Chapter 3.docx

**Chapter 3** **Prenatal Development and Birth** **Conception** The first step in the development of an individual human being happens at conception, when each of us receives a combination of genes that will shape our experiences throughout the rest of our lives. **The Process of Conception** Typically, a woman releases one egg cell (ovum) from one of her ovaries each month, around the middle of her menstrual cycle. If the ovum isn't fertilized, it travels down the fallopian tube to the uterus, where it disintegrates and is expelled during menstruation. However, if intercourse occurs during the few days when the ovum is in the fallopian tube, a sperm cell from the male's ejaculation may travel through the woman's reproductive system and fertilize the ovum. **Conception** Every cell in the human body contains 23 pairs of chromosomes, or strings of genetic material. However, sperm and ovum, collectively called gametes, contain 23 single (unpaired) chromosomes. At conception, the chromosomes from the egg and sperm combine to form 23 pairs in a new cell, the zygote. Twenty-two of these pairs, known as autosomes, carry most of the genetic information. The 23rd pair, the sex chromosomes, determine the sex of the individual. The X chromosome, one of the two sex chromosomes, is large and carries many genes, while the Y chromosome is small and carries few genes. Zygotes with two X chromosomes develop into females, and those with one X and one Y chromosome develop into males. As a woman's cells only contain X chromosomes, all her eggs carry X chromosomes. A man's sperm is split evenly between X and Y chromosomes, so the sex of the offspring is determined by the sex chromosome in the sperm. **Multiple Births** Most human infants are conceived and born individually. However, about 3.1 out of every 100 births in Canada result in multiple births, typically twins. Approximately two-thirds of these twins are fraternal, or dizygotic, originating from two separate sets of eggs and sperm. These twins are genetically as similar as any pair of siblings and can be of different sexes. The remaining one-third are identical, or monozygotic, twins, resulting from a single zygote that splits into two. As they develop from the same zygote, identical twins start life with identical genes. Research involving identical twins is a key strategy in behavior genetics. The annual number of multiple births in Canada has risen by about a third since the 1990s. This increase is partly due to the growing number of women over 35 giving birth for the first time. Two factors link multiple births to maternal age. Firstly, women over 35 are more likely to naturally conceive multiples, though the reasons for this are not fully understood. Secondly, women over 35 are more likely to have difficulties conceiving and therefore more likely to undergo assisted human reproduction procedures, including ovulation stimulation drugs. Women of all ages who use these procedures have a higher likelihood of multiple births compared to those who conceive naturally. **Assisted Human Reproduction** Assisted human reproduction (AHR) and related research are now regulated in Canada. The updated legislation safeguards the health and well-being of Canadians undergoing AHR treatment and the children born as a result. It also outlines the requirements and restrictions related to reproductive materials like sperm, ova, and embryos, the provision of services, and research and technologies. **Research Report** **Twins in Genetic and Epigenetic Research** Researchers in developmental psychology have long compared identical and fraternal twins to understand heredity's role in human development. The premise is that if identical twins (who share the same genes) raised apart are more similar than fraternal twins or non-twin siblings (who share similar, but not identical genes) raised together, then heredity influences the trait under study. For instance, correlations from several studies on twins' intelligence test scores suggest a stronger relationship the closer the correlation is to +1.00. Here are the correlations: - Identical twins reared together: **0.86** - Identical twins reared apart: **0.72** - Fraternal twins reared together: **0.60** - Non-twin siblings reared apart: **0.24** As you can see, intelligence test scores are more strongly correlated in identical twins than in fraternal twins or non-twin siblings, even when the identical twins are raised in different families. These numbers indicate a significant role of heredity in intelligence. Researchers from the University of Western Ontario and the University of British Columbia in Canada have studied the heritability of attitudes. They surveyed 195 pairs of identical twins and 141 pairs of fraternal twins and found that genetic factors accounted for about 35% of the differences in attitudes. The study revealed a high genetic influence on twins' attitudes towards various issues, activities, and social settings, such as abortion on demand, roller-coaster rides, playing organized sports, and the death penalty for murder. The studies indicate that both intelligence and attitudes have a strong genetic basis. However, the role of the environment is also significant. This is evident from the fact that identical twins, even those raised in the same home, do not have perfect correlation (+1.00) in terms of these psychological traits. This suggests that factors beyond genetics, such as environment, play a crucial role. Furthermore, the correlation decreases for identical twins raised separately, reinforcing the influence of the environment. Scientists are examining prenatal development components, including genetic, environmental, epigenetic, and intrauterine factors, to understand phenotypic differences. They've found that monozygotic twins, despite originating from a single zygote, can develop minor genetic differences post zygote division. Maternal environmental factors like diet, stress, and exposure to adverse conditions during pregnancy also influence phenotypic differences. The epigenome, which can both modify and be modified by in utero conditions, plays a significant role. Over a lifetime, lifestyle variables such as diet, smoking, fitness, and stress levels can further alter epigenetic markers in identical twin pairs, leading to phenotypic changes, including disease frequency and onset. Fertility drugs and in vitro fertilization (IVF) are among the Assisted Human Reproduction (AHR) procedures available to couples facing fertility issues. IVF, also known as the "test-tube baby" method, involves fertilizing an egg and sperm in a lab dish and then implanting the embryo into a woman's uterus. The egg and sperm can come from the prospective parents or donors. In IVF labs, numerous embryos are typically created and cryopreserved before implantation. Newer cryopreservation methods involve using cryoprotectants and super-cooled liquid nitrogen to freeze the embryos almost instantly. This vitrification protocol significantly enhances the survival rate of embryos during thawing, implantation, and pregnancy. It also reduces the need for multiple embryo transfers, thereby lowering the risk of multiple gestations. Several studies, including a large-scale Australian one, have found no significant side effects of cryopreservation on children's development. However, the success rate of IVF is not high, particularly for older women. About 31% of Canadian women under 35 achieve a live birth through IVF, but the success rate drops to around 15% for women over 40. While younger women can harvest, freeze, and store their eggs for future use, there's no guarantee that these "younger" eggs will increase the chances of successful fertilization when these women are older. Multiple births are more common with IVF due to the practice of transferring several embryos at once, increasing risks for both mother and babies. This has sparked a global debate on defining successful Assisted Human Reproduction (AHR) outcomes. Some argue for a single, term-gestation, live baby per fertility cycle, while others consider one or more babies as success, provided couples are aware of the associated risks. Single Embryo Transfer (SET) is likely to become the international norm in IVF treatment, with Nordic countries already having high SET rates (\~70%) and a consistent \~30% pregnancy rate per embryo transfer. To reduce multiple births from IVF, Canadian guidelines recommend transferring no more than two embryos for women under 35 and no more than four for women over 39, unless there are exceptional circumstances. Artificial insemination, a technique where sperm are directly injected into a woman's uterus during her fertile period, is more successful and less likely to result in multiple births than IVF. The sperm can be from the woman's partner or a donor, making it a viable option for couples with male fertility issues or for women who wish to conceive without a male partner. However, it carries some infection risk as it is invasive. Assisted human reproductive techniques have raised concerns, especially when anonymous donors are involved, as it's impossible to determine the children's genetic heritage. To address this, Canada's Assisted Human Reproduction Act mandates a personal health information registry with non-identifying medical information about the donors, allowing children conceived through donations to access their medical histories. **Pregnancy and Prenatal Development** Pregnancy is a state where a woman's body nurtures a developing embryo or fetus. Prenatal development, also known as gestation, is the transformation of a zygote into a newborn. The process culminating in childbirth encompasses two distinct experiences: those of the pregnant woman and the developing zygote, embryo, and fetus. **The Mother's Experience** Pregnancy is customarily divided into trimesters, three periods of three months each. +-----------------+-----------------+-----------------+-----------------+ | **Trimester** | **Events** | **Prenatal | **Serious | | | | Care** | Problems** | +=================+=================+=================+=================+ | First | -Missed period | -Confirmation | -Ectopic | | trimester: From | | of pregnancy | pregnancy | | first day of | -Breast | | | | last menstrual | enlargement | -Calculation of | -Abnormal urine | | period (LMP) to | | due date | or blood tests | | 12 weeks after | -Abdominal | | | | LMP | thickening | -Blood and | -Increased | | | | urine tests | blood pressure | | | | (and other | | | | | tests, if | -Malnutrition | | | | needed) | | | | | | -Bleeding | | | | -Monthly doctor | | | | | visits to | -Miscarriage | | | | monitor vital | | | | | functions, | | | | | uterine growth, | | | | | weight gain, | | | | | and sugar and | | | | | protein in | | | | | urine | | +-----------------+-----------------+-----------------+-----------------+ | Second | -Weight gain | -Monthly doctor | -Gestational | | trimester: From | | visits continue | diabetes | | 12 weeks after | \- "Showing" | | | | LMP to 24 weeks | | -Ultrasound to | -Excessive | | after LMP | -Fetal | measure fetal | weight gain | | | movements felt | growth and | | | | | locate placenta | -Increased | | | -Increased | | blood pressure | | | appetite | | | | | | | -Rh | | | | | incompatibility | | | | | of mother and | | | | | fetus | | | | | | | | | | -Miscarriage 13 | | | | | to 20 weeks | | | | | | | | | | -Premature | | | | | labour 21+ | | | | | weeks | +-----------------+-----------------+-----------------+-----------------+ | Third | -Weight gain | -Weekly visits | -Increased | | trimester: From | | beginning at | blood pressure | | 25 weeks after | -Breast | 32nd week | | | LMP to | discharge | | -Bleeding | | beginning of | | -Ultrasound to | | | labour | | assess position | -Premature | | | | of fetus, if | labour | | | | needed | | | | | | -Bladder | | | | -Treatment of | infection | | | | Rh | | | | | incompatibility | | | | | , | | | | | if needed | | | | | | | | | | -Pelvic exams | | | | | to check for | | | | | cervical | | | | | dilation | | +-----------------+-----------------+-----------------+-----------------+ **First Trimester** Pregnancy starts when the zygote implants in the woman's uterus lining. The zygote releases chemicals that halt the woman's menstrual cycle. Some of these chemicals are expelled in the urine, enabling pregnancy detection shortly after conception. Other chemicals trigger physical changes like breast enlargement. During pregnancy, the cervix thickens and produces mucus to protect the developing embryo from harmful organisms. The uterus shifts position, exerting pressure on the bladder and leading to frequent urination. Other symptoms like fatigue and breast tenderness may disrupt sleep. Morning sickness, characterized by nausea and often vomiting, is another common symptom that can occur at any time of the day or night. First trimester prenatal care is crucial to prevent congenital anomalies as all the baby's organs form during the first eight weeks. Early prenatal care can detect maternal conditions like STIs that could affect prenatal development. Health professionals can advise women to avoid drugs and alcohol early in prenatal development to prevent congenital anomalies. Early prenatal care is also vital for the pregnant woman's health. For instance, in rare cases, a zygote implants in a fallopian tube instead of the uterus, resulting in an ectopic pregnancy. Early surgical removal of the zygote is essential for the woman's future fertility. Approximately **15%** of pregnancies result in miscarriage, also known as spontaneous abortion. An early-term miscarriage can resemble a menstrual period from a woman's perspective, but usually involves more discomfort and blood loss. After a late-term miscarriage, medical attention is crucial as the woman's body might not fully expel the embryo. **Second Trimester** During the **second trimester** of pregnancy, which spans from the end of **week 12 to week 24**, morning sickness typically subsides, leading to an increased appetite. The woman gains weight as the uterus expands to accommodate the growing fetus. As a result, the pregnancy becomes visible, or the woman begins to "show". Additionally, the woman starts to feel the fetus's movements, usually between the **16th and 18th weeks**. During monthly prenatal checkups, both the mother's and baby's vital functions are monitored, and the baby's growth in the womb is tracked. Ultrasound tests are typically conducted, and the baby's sex can be identified after about the **13th week**. Monthly urine tests are performed to check for gestational diabetes, a type of diabetes that occurs only during pregnancy. If a woman has any form of diabetes, including gestational diabetes, she must be closely monitored during the **second trimester**. This is because her baby may grow too quickly, potentially leading to premature labor or a baby that is too large for vaginal delivery. The risk of miscarriage decreases in the **second trimester**, but a small number of fetuses may still die between the **13th and 20th weeks** of pregnancy. Premature labor after the **21st week** can lead to the birth of a living but extremely small baby. While a small percentage of these infants survive, the majority face significant health challenges. **Third Trimester** At **25 weeks**, a woman enters her **third trimester** of pregnancy, characterized by weight gain and abdominal enlargement. The woman's breasts may start to secrete colostrum in preparation for nursing. During the third trimester, most women feel a stronger emotional connection to the fetus. Individual fetal behaviors, such as hiccupping or thumb-sucking, may become apparent in the final weeks of pregnancy. Additionally, most women observe regular periods of activity and rest in the fetus. Prenatal checkups continue monthly until **week 32**, after which most women start weekly visits to their doctor or midwife. Monitoring blood pressure becomes crucial as some women may develop a life-threatening condition called **toxemia of pregnancy** during the third trimester. This condition, signaled by a sudden increase in blood pressure, can lead to a stroke in a pregnant woman. **Prenatal Development** The prenatal period is the stage in the human lifespan where change happens most rapidly. This process follows two developmental patterns: - **Cephalocaudal pattern**: Development starts from the head and moves downward. For instance, the brain forms before the reproductive organs. - **Proximodistal pattern**: Development proceeds in an orderly manner from the body's centre towards the extremities. In other words, structures closer to the body's centre, like the rib cage, develop before the fingers and toes. **Table 3.2 Milestones of Prenatal Development** +-----------------------------------+-----------------------------------+ | Stage/Timeframe | Milestones | +===================================+===================================+ | Germinal Stage | Sperm and ovum unite, forming a | | | zygote containing genetic | | Day 1: Conception | instructions for the development | | | of a new and unique human being. | +-----------------------------------+-----------------------------------+ | Days 10 to 14: Implantation | The zygote burrows into the | | | lining of the uterus. Specialized | | | cells that will become the | | | placenta, umbilical cord, and | | | embryo are already formed. | +-----------------------------------+-----------------------------------+ | Embryonic Stage | All the embryo's organ systems | | | form during the six-week period | | Weeks 3 to 8: Organogenesis | following implantation. | +-----------------------------------+-----------------------------------+ | Fetal Stage | The fetus experiences significant | | | growth, from **2.5 cm and 7 g** | | Weeks 9 to 38: Growth and Organ | to approximately **51 cm and 3.2 | | Refinement | kg**. By the **12th week**, the | | | sex of most fetuses can be | | | determined. Viability becomes | | | possible by the **24th week** due | | | to changes in the brain and | | | lungs, but optimal development | | | requires an additional **14 to 16 | | | weeks** in the womb. Most neurons | | | form by the **28th week**, with | | | their connections starting to | | | develop soon after. In the final | | | eight weeks, the fetus gains the | | | ability to hear and smell, | | | becomes sensitive to touch, | | | responds to light, and even | | | begins to learn. | +-----------------------------------+-----------------------------------+ **The Germinal Stage** The **germinal stage** of gestation spans the first two weeks, from conception to implantation. In this stage, cells differentiate into two types: those that will form the fetus's body and those that will create the structures necessary for its development. Cell division occurs swiftly, and by the fourth day, the zygote comprises dozens of cells. By **day 5**, cells form a hollow, fluid-filled sphere known as a blastocyst. Within the blastocyst, cells that will eventually form the embryo start to cluster together. On **day 6 or 7**, the blastocyst contacts the uterine wall and by the **12th day**, it is fully embedded in the uterine tissue, a process known as implantation. Some cells from the blastocyst's outer wall merge with uterine lining cells to start forming the placenta, an organ that facilitates the transfer of oxygen, nutrients, and other substances between the mother's and baby's blood. The placenta's specialized structures allow the mother's and baby's blood to come close without mixing. Like the zygote, the placenta secretes hormones that halt the mother's menstrual periods and maintain the connection between the placenta and the uterus. Other hormones from the placenta make the woman's pelvic bones more flexible, induce changes in the breasts, and increase the mother's metabolic rate. Simultaneously, the blastocyst's inner cells start to specialize. One cell group forms the umbilical cord, which connects the embryo to the placenta, and its vessels carry blood to and from the mother. Other cells form the yolk sac, which produces blood cells until the embryo's blood-cell-producing organs develop. Some cells form the amnion, a fluid-filled sac where the baby floats until just before birth. By the **12th day**, the cells that will form the embryo's body are also formed. **The Embryonic Stage** The **embryonic stage** starts at implantation, about two weeks post-conception, and lasts until the end of the **8th week**. By the time many women suspect they're pregnant, typically three weeks after conception, the embryo's cells begin to specialize and unite to lay the groundwork for all the body's organs. For instance, neurons, the nervous system cells, form a structure known as the neural tube, which will develop into the brain and spinal cord. A primitive heart and kidney precursors also form during the **3rd week**, along with three sacs that will evolve into the digestive system. In **week 4**, the embryo's neural tube expands to form the brain, spots that will become eyes appear, the heart starts beating, and the backbone and ribs become visible as bone and muscle cells align. The face begins to form, and the endocrine system starts developing. By **week 5**, the embryo, now about 6.5 millimetres long and 10,000 times larger than the zygote, shows rapid development of arms and legs. Each hand displays five fingers, and the eyes develop corneas and lenses. The lungs also start to form. In **week 6**, the embryo's brain starts producing electrical activity patterns, and it begins to move in response to stimuli. The gonads or sex glands (ovaries in females and testes in males) develop, their development being dependent on the presence or absence of androgens (male sex hormones, such as testosterone). In the presence of androgens, the gonads become testes, while in their absence, the gonads develop into ovaries. During the 7th week of embryonic development, embryos start to move spontaneously. They have visible skeletons and fully developed limbs. The bones start to harden, and muscles mature, allowing the embryo to maintain a semi-upright posture. The eyelids close to protect the developing eyes, and the ears are fully formed. Tooth buds can be detected in the jawbones through X-rays. In the 8th week, the final week of the embryonic stage, the liver and spleen start functioning, enabling the embryo to produce and filter its own blood cells. The heart is well developed and pumps blood efficiently throughout the body. The embryo's movements increase as its brain's electrical activity becomes more organized. Connections between the brain and the rest of the body are well established, and the digestive and urinary systems are functional. By the end of the 8th week, organogenesis, or organ development, is complete. **The Fetal Stage** The fetal stage is the final phase of prenatal development, starting from the end of the 8th week until birth. During this stage, the fetus grows from approximately 2 grams and 2.5 centimeters to a newborn baby weighing around 3.2 kilograms and measuring about 50 centimeters at around 38 weeks. This stage is characterized by the refinement of organ systems, particularly the lungs and brain, which are crucial for survival outside the womb. A small number of babies born as early as weeks 20 or 21 can survive. By the end of week 22, viability, or the ability to live outside the womb, is achieved by 20 to 33% of babies. If a baby remains in the womb until the end of week 23, their survival chances increase to 38 to 58%. By the end of week 24, the survival rate rises to 58 to 87%. The additional weeks in the womb likely enhance lung function efficiency. Nowadays, most premature babies are treated with drugs that speed up lung development, leading to a significant increase in the survival rates of even the earliest-born preemies since the beginning of the 21st century. **The Fetal Brain** While the foundational structures of all body's organ systems are formed during the embryonic stage, most brain development and refinement occurs during the fetal stage. Neurons, the specialized cells of the nervous system, start developing as early as week 3 of the embryonic stage. However, the rate of neural formation significantly accelerates between the 10th and 18th weeks of the fetal stage, a process referred to as neuronal proliferation. Between the 13th and 21st weeks of fetal development, newly formed neurons migrate to their permanent locations in the brain. During migration, neurons consist only of cell bodies, which contain the nucleus and carry out all vital cell functions. Once neurons reach their final destinations, they begin to form connections, or synapses. ![](media/image2.png)Synapses are tiny spaces where neural impulses travel from one neuron to another via neurotransmitters, the chemical messengers. Changes in fetal behavior, such as alternating periods of activity and rest and the onset of yawning, indicate that synapse formation is taking place. These observable changes reassure physicians that fetal brain development is progressing normally. Synapse formation necessitates the growth of two neuronal structures: axons and dendrites. Axons, tail-like extensions, can range from **1 to 200 millimetres** in length within the brain and can even grow over a metre long, such as between the spinal cord and the body's extremities. Dendrites are tentacle-like branches extending from the cell body. Dendrite development is believed to be highly susceptible to negative environmental factors like maternal malnutrition and placental functioning defects. Alongside neuronal migration, glial cells start to develop. These cells act as the "glue" that binds neurons together, shaping the major structures of the brain. As a result, the brain starts to take on a more mature appearance, which can be observed using modern technologies like magnetic resonance imaging (MRI). **Sex Differences** Between the 4th and 8th week of conception, the **SRY gene** on the Y chromosome triggers the male embryo to start producing **androgens**. These hormones are crucial for the development of the gonads-**testes in males** and **ovaries in females**. They also lead to the formation of male genitals. In the absence of androgens, female genitals develop regardless of the embryo's chromosomal status. Female embryos exposed to androgens, due to the mother's medication or a genetic disorder like **congenital adrenal hyperplasia**, can develop genitals that appear male. Prenatal androgens influence the development of the brain, but sex differences in the brain don't always lead to sex differences in behavior. However, there are structural differences in the prenatal brain, with some regions being larger (due to more densely packed neurons) and others smaller. This results in certain areas of the brain being more masculine in males and more feminine in females. These differences may contribute to sex differences in cognitive functioning, spatial and verbal abilities, physical aggression, communication skills, and sexual orientation development later in life. They may also play a role in neuropsychiatric disorders like major depressive disorder in females and autism spectrum disorders in males. It's also becoming clear that all body organs are sexually differentiated to some extent, which could explain sex differences in disease patterns later in life. Before birth, there are distinct growth patterns in boys and girls during the second and third trimesters. Females tend to grow more slowly as determined by measures like head width and circumference, femur length, weight, and overall length. Male fetuses are more responsive to touch, while female fetuses are more responsive to sounds. Despite newborn boys being typically longer and heavier, female infants are one to two weeks ahead in bone development at birth. This advantage in skeletal development continues through childhood and early adolescence, enabling girls to acquire coordinated movements and motor skills, especially those involving the hands and wrists, earlier than boys. The gap widens each year until mid-teens, when boys catch up and surpass girls in general physical coordination. **Prenatal Behaviour** Before the scientific study of prenatal development, pregnant women observed fetal responses to sounds. Modern techniques like ultrasound imaging and fetal heart rate monitoring have significantly increased our understanding of fetal behavior. By the 32nd or 33rd week, fetuses can distinguish between familiar and novel stimuli. Newborns seem to remember prenatal stimuli such as their mother's heartbeat, the smell of amniotic fluid, and stories or music heard in the womb. For instance, when fetuses were exposed to their mother's voice and a stranger's voice reading the same poem, they showed different heart-rate patterns, suggesting they can recognize their mother's voice. Individual behavioral differences are also noticeable in fetuses. Studies have shown that very active fetuses tend to become very active children. Conversely, less active fetuses who are more responsive to maternal stimulation are more likely to be fearful and shy as children. **Issues in Prenatal Development** Prenatal development can be affected by external factors, but most of these issues are rare, preventable, and don't necessarily lead to lasting effects on the child. In Canada, approximately **4.3%** of newborns have a congenital anomaly, which is an abnormality present at birth that could cause physical or mental disability, or even death. **Genetic Disorders** Many disorders are inherited through the function of dominant and recessive genes. Autosomal disorders are caused by genes on autosomes, which are chromosomes that are not sex chromosomes. Sex-linked disorders, on the other hand, are caused by genes located on the X chromosome. **Autosomal Disorders** Most disorders caused by recessive genes are identified in infancy or early childhood. For instance, a recessive gene can lead to a condition known as phenylketonuria (PKU), which affects a baby's ability to digest the amino acid phenylalanine. This can result in toxin accumulation in the brain and developmental delay. PKU occurs in about 1 in every 12,000 to 17,000 babies. If a baby with PKU avoids foods containing phenylalanine, they can prevent intellectual delay. Since milk contains phenylalanine and is harmful to PKU babies, early diagnosis is crucial. Therefore, all Canadian provinces conduct universal PKU screening shortly after birth. PKU, like many recessive disorders, is more common in Caucasian babies compared to other ethnic groups. Similarly, sickle-cell disease, another recessive disorder that causes red blood cell abnormalities, is more prevalent among West African and African American infants. Sickle-cell disease can lead to insufficient oxygen supply to the body's tissues. However, with early diagnosis and antibiotic treatment, over **90%** of children diagnosed with the disease can survive into adulthood. Tay-Sachs disease, a recessive disorder, affects 1 in every 3000 babies born to couples of Eastern European Jewish descent. French Canadians in the Gaspé region of Québec are also at risk, carrying the gene for a severe form of Tay-Sachs disease at a rate 10 times higher than the general population. Babies with Tay-Sachs are likely to experience severe intellectual delay and blindness, with very few surviving past the age of 3. Disorders caused by dominant genes, like Huntington's disease, are typically diagnosed in adulthood. This disease leads to brain deterioration and impacts both psychological and motor functions. In Canada, the risk of Huntington's is **1 in 10,000**, and a child with a parent who has Huntington's has a **50%** chance of developing the disease. A blood test can now detect the Huntington's gene, enabling individuals with a parent with this disease to make informed decisions about having children and preparing for the potential onset of this serious disorder in their later years. **Sex-Linked Disorders** Most sex-linked disorders are caused by recessive genes. A common one is red-green color blindness, which affects **7 to 8%** of men and **0.5%** of women, making it difficult for them to distinguish between adjacent red and green colors. However, most people learn to compensate for this and lead normal lives. Hemophilia is a more serious sex-linked recessive disorder. People with hemophilia lack the blood clotting components, causing their bleeding to not stop naturally. This disorder is found in approximately **1 in 5000** baby boys and is almost unknown in girls. Fragile-X syndrome is another sex-linked disorder, affecting **1 in 4000** males and **1 in 8000** females. Individuals with this disorder have a "fragile" or damaged spot on the X chromosome, which can cause developmental delay that worsens as the child ages. **Chromosomal Errors** A variety of problems can be caused by a child having too many or too few chromosomes, a condition referred to as a chromosomal error or chromosomal anomaly. Like genetic disorders, these are distinguished by whether they involve autosomes or sex chromosomes. **Trisomies** Trisomy is a condition where a child has three copies of a specific autosome. The most common is trisomy 21, also known as Down syndrome, where the child has three copies of chromosome 21. This leads to intellectual delay, distinctive facial features, and potential health issues like hypothyroidism, hearing loss, or heart anomalies. In Canada, the incidence of this anomaly has remained steady, averaging **1 in \~750 births**. Mothers over the age of 35 are at the highest risk of having a child with trisomy 21, accounting for **\~48%** of all Down syndrome births, but only **\~19%** of all live births. Trisomies have also been identified in the 13th and 18th pairs of chromosomes. These disorders are more severe than trisomy 21, with few children with trisomy 13 or trisomy 18 living past the age of 1 year. The likelihood of having a child with one of these disorders also increases with a woman's age. **Sex-Chromosome Anomalies** Sex chromosome anomalies include conditions like Klinefelter's syndrome and Turner's syndrome: **Klinefelter's syndrome (XXY)** is the most common, occurring in **1 or 2 out of every 1000 males**. Boys with this condition typically appear normal but have underdeveloped testes and low sperm production in adulthood. While most are not intellectually delayed, many have language and learning disabilities. At puberty, they undergo both male and female changes, such as penis enlargement and breast development. ![](media/image4.png)**Turner's syndrome (XO)** affects individuals who are anatomically female but exhibit stunted growth. They also have a higher risk of malformations in internal organs like the heart and kidneys. Without hormone therapy, most do not menstruate or develop breasts at puberty. However, about **10%** experience normal puberty and can conceive and carry children to term. Many others can achieve successful pregnancies with the help of donor ova. **Teratogens: Maternal Diseases** Prenatal development can be affected by teratogens, which are agents that can harm an embryo or fetus. Each organ system is most susceptible to damage when it's developing the fastest. As most organ systems develop rapidly during the first eight weeks of gestation, this period carries the highest risk of teratogen exposure. The discussion on teratogens begins with a look at viral infections. **Viral Infections** Certain viruses can penetrate the placental barriers and directly affect the embryo or fetus. Rubella, or German measles, for instance, causes a brief, mild reaction in adults but can be fatal to a fetus. Most infants exposed to rubella during the embryonic stage may experience some level of hearing loss, visual impairment, and/or heart anomalies. It's recommended that standard vaccinations be updated before pregnancy, and some vaccines, like the influenza vaccine, are safe for both the mother and baby during pregnancy. Insect-borne diseases, such as the Zika virus transmitted by mosquitoes, pose significant risks to fetal development. Prenatal risks of Zika infection include adverse birth outcomes like microcephaly and other neurological deficits. Until an effective vaccine is available, pregnant women or those planning a pregnancy should take extra precautions to avoid Zika infection, especially when traveling to warmer regions of the Americas and Caribbean. For safety, they can check the Government of Canada's travel health notices before planning a trip. Cytomegalovirus (CMV), a lesser-known viral infection from the herpes group, is transmitted through body fluids. Up to **60%** of all women carry CMV, but most are asymptomatic. A Canadian study found that **0.2 to 2.4%** of babies whose mothers have CMV get infected prenatally. The risk to the fetus is highest when the mother gets infected or has a reactivation of the infection during pregnancy. About **10%** of infected newborns show serious CMV symptoms, including deafness, central nervous system damage, and intellectual delay. Additionally, **5 to 17%** of infected newborns who don't initially show symptoms later develop varying degrees of abnormality. HIV, the virus causing AIDS, can be transmitted from mother to fetus. It can cross the placenta, be contracted during delivery, or passed through breast milk. The HIV infection rate among pregnant women in Canada is estimated at **2 per 1000**. Interestingly, a Canadian study found that **60%** of HIV-infected women intend to become pregnant. However, it's been shown that HIV-positive pregnant women who take anti-HIV drugs, give birth via Caesarean section, and feed their babies formula significantly reduce the risk of transmitting the disease to their children. Infants who contract HIV from their mothers usually fall sick within the first two years of life due to the virus weakening their immune systems. This vulnerability allows other infectious agents, like the bacteria causing pneumonia and meningitis, to invade their bodies. Even if they don't show symptoms, these children must limit their exposure to viruses and bacteria. Notably, HIV-positive children cannot receive vaccines using live viruses, such as the polio vaccine. Several sexually transmitted infections (STIs) such as syphilis, genital herpes, and gonorrhea can lead to various congenital anomalies. The bacterium causing syphilis is particularly harmful during the last 26 weeks of prenatal development, leading to anomalies in the eyes, ears, and brain. Genital herpes, typically transmitted from mother to infant during birth, results in death for a third of infected babies, while another 25 to 30% experience blindness or brain damage. Therefore, doctors often recommend surgical delivery for women with herpes. Gonorrhea, which can cause blindness in infants, is also usually transmitted during birth. To prevent damage from gonorrhea, newborns' eyes are typically treated with a special ointment. **Teratogens: Drugs** Any drug, even those generally considered safe like antibiotics, can potentially cause birth defects. Therefore, doctors usually inquire about the possibility of pregnancy in women of childbearing age before prescribing medications. Unless a drug is crucial for a woman's health, it's recommended to avoid all drugs during pregnancy. Determining the effects of various drugs (both prescription and nonprescription, legal, and illicit) on prenatal development is complex, as many pregnant women take multiple drugs. Other factors such as maternal stress, lack of social support, poverty, and inadequate prenatal care often coincide with illegal drug use. Despite these complexities, several drugs appear to impact infant development independently of other factors. **Prescription and Over-the-Counter Drugs** The thalidomide tragedy of the 1960s involved a mild tranquilizer prescribed to pregnant women for severe morning sickness. Unfortunately, this drug led to serious limb malformations in thousands of exposed fetuses. Moreover, even common prescription drugs used for anxiety and depression, such as benzodiazepine tranquilizers and selective serotonin reuptake inhibitors (SSRIs), have been found to have teratogenic effects. Benzodiazepines are linked with increased risks of preterm delivery, low birth weight, low Apgar score, neonatal intensive-care-unit admissions, and respiratory distress syndrome. SSRIs have been associated with preterm deliveries among women who started treatment after the first trimester. While doctors generally recommend avoiding unnecessary medications during pregnancy, some pregnant women may need to take certain drugs to manage health conditions that could pose risks to both them and their unborn children. These conditions can include epilepsy, heart diseases, diabetes, asthma, and certain psychiatric disorders. In these cases, the benefits of the medication are weighed against potential teratogenic effects. The goal is to find a balance where the mother's condition is effectively managed with a drug and dosage that minimizes risk to the unborn child. Unlike prescription drugs, over-the-counter medicines are often taken casually without a doctor's consultation. Many, like acetaminophen, are generally safe for pregnant women unless overused. However, it's recommended that pregnant women discuss their regular medications, including vitamins and supplements, with their doctors at the start of their pregnancy. This allows doctors to advise on the safety of these substances and suggest safer alternatives if needed. Typically, doctors prefer older, thoroughly tested drugs. **Tobacco** Infants born to mothers who smoke tend to be about 150 grams lighter than those born to non-smoking mothers, which can lead to various short and long-term risks. Smoking during pregnancy is associated with higher rates of miscarriage, stillbirth, premature birth, neonatal death, low birth weight, and neurobehavioral disorders. However, smoking rates during pregnancy are declining in Canada, now at about 12%. Younger women (15-24 years) are more likely to smoke during pregnancy, but about half quit by their third trimester. **Alcohol** Research shows that alcohol can negatively impact prenatal development, affecting an ovum even before ovulation or during its journey to the uterus. A zygote can also be affected by alcohol before it implants in the uterine lining. Heavy drinkers or those with an alcohol use disorder are at a significant risk of having infants with fetal alcohol syndrome (FAS). These children are typically smaller with smaller brains, often have heart anomalies and hearing losses, and distinctive facial features such as small, wide-set eyes, a somewhat flattened nose, a thin upper lip, and a long, flattened space between the nose and mouth. As they grow, they are usually shorter with smaller heads, and their intelligence test scores often indicate a mild developmental delay. Even those FAS children without intellectual delays often face learning and behavioral difficulties. Fetal Alcohol Spectrum Disorder (FASD) is a term used to describe a range of effects caused by alcohol consumption during pregnancy. It includes Fetal Alcohol Syndrome (FAS) at one end, characterized by severe effects, and Fetal Alcohol Effects (FAE) at the other, representing milder or partial effects. A child with FAE may not show physical signs of FAS, but secondary issues like mental health problems or learning and behavioral difficulties may emerge during childhood. In Canada, the prevalence of FASDs is approximately 0.5% and FAS is about 0.1% in the general population. However, these rates are estimated to be 16 times and 38 times higher, respectively, among Indigenous populations. In Canada, alcohol consumption during pregnancy is decreasing, with about 10% of pregnant women reporting alcohol use. However, 3% of these women engage in binge drinking and 5% admit to drinking throughout their pregnancy. The rates are significantly higher among Indigenous women, with 40% consuming alcohol and about 22% binge drinking during pregnancy. Both younger (under 21) and older (over 30) women are more likely to consume alcohol during pregnancy than those aged 21 to 30. Even moderate drinking can lead to learning and behavioral difficulties in children. Therefore, the safest course is for pregnant women to abstain from alcohol completely. This also applies to women trying to conceive, as they may unknowingly continue to drink into their first trimester. A concerning finding is that women who smoked during pregnancy were also more likely to consume alcohol, amplifying the risks to the developing fetus. Research on the effects of marijuana use during pregnancy has been mixed, partly due to the previous illegality of non-medical cannabis use in Canada until October 2018, which hindered comprehensive research. It's also challenging to isolate the effects of cannabis as pregnant users are more likely to also smoke cigarettes, drink alcohol, and use other illicit substances. However, cannabinoids like THC do pass from the mother to the fetus, affecting both. Consistent findings suggest that marijuana use during pregnancy can lead to reduced preterm growth rate, size, and weight, increased spontaneous preterm births, and more neonatal care unit admissions. Emerging evidence also suggests potential neurobehavioral and neurocognitive risks associated with smoking cannabis during pregnancy and breastfeeding. **Illicit Drugs** Both heroin and methadone, often used to treat heroin addiction, can lead to miscarriage, premature labor, and early death. Additionally, 60 to 80% of babies born to heroin-addicted mothers are also addicted, experiencing withdrawal symptoms like high-pitched cries, irritability, tremors, vomiting, convulsions, and sleep problems that can last up to four months. Cocaine use by pregnant women is linked to developmental issues in children. However, it's challenging to isolate the effects of cocaine from other factors like poverty and use of other substances. Some studies suggest that cocaine alone may not have long-term effects on cognitive or social development. Yet, it can cause pregnancy complications like placental disruption and premature labor, negatively affecting the fetus. Increased prenatal substance exposure is associated with behavioral problems by age 5, impacting physical and psychological outcomes throughout life. **Teratogens: Other Harmful Influences on Prenatal Development** Maternal factors such as diet, age, and physical and mental health can negatively impact prenatal development. These characteristics can indirectly affect prenatal development by altering the genetic expression and consequently, the functioning of the placenta. **Diet** Certain nutrients, such as folic acid, are crucial for prenatal development. Found in foods like beans and spinach, insufficient folic acid is linked to neural tube defects like spina bifida. These effects can occur early in pregnancy, often before a woman realizes she's pregnant. Therefore, it's recommended that women planning to conceive consume at least 400 micrograms of folic acid daily. A study in Québec found that multivitamin supplements can compensate for lower levels of micronutrients from diet, but they can also raise iron and folic acid levels above the recommended amounts. Despite supplementation, dietary intake of fiber and potassium often remains low, while sodium and fat intake tend to exceed recommended levels. Adequate calorie and protein intake is crucial for pregnant women to prevent malnutrition. Malnutrition during pregnancy, especially in the last three months, increases the risk of delivering a low-birth-weight infant (under 2500 grams) who may face intellectual challenges in childhood. Prenatal malnutrition, along with various obstetrical complications, has been identified as a significant risk factor for the development of mental disorders in adulthood. The impact of maternal malnutrition is most profound on the developing nervous system. Studies on rats have shown that restricted protein intake during fetal and early postnatal periods leads to reduced brain weight and learning capacity. Similar effects have been observed in human studies where severe prenatal malnutrition led to fetal or newborn death. These infants had smaller brains and fewer, smaller brain cells. Furthermore, studies suggest that the adverse effects of prenatal malnutrition can persist throughout the individual's lifespan. Canadian guidelines recommend that a woman with a normal body mass index (BMI) should gain between 11.5 to 16.0 kilograms during a single pregnancy. Underweight women should gain more, while overweight or obese women should gain less. By following Canada's Food Guide and the Healthy Eating and Pregnancy guidelines from early pregnancy, a woman is likely to achieve the necessary weight gain. Adhering to dietary guidelines is particularly challenging for pregnant Indigenous women in remote communities due to limited access to nutritious food. To cope with food insecurity, these communities have altered consumption patterns, resorting to more rationing and food sharing. There's been an increased reliance on store-bought food, which often makes healthy options less affordable than calorie-dense, nutrient-poor foods like processed items high in sugar and fat. This is problematic for pregnant women whose nutritional needs increase. On average, ultra-processed foods now make up over half of the calories in Indigenous diets. While traditional foods remain a moderate source of protein and essential nutrients, there's been a shift away from hunting, fishing, and gathering due to increasing costs. This shift is exacerbated by reduced availability of traditional foods due to climate change, diminished game, and plant stocks, and in some cases, environmental and biological contamination. **Age** In Canada, there's been a trend since the early 1990s of women delaying their first pregnancy until their 30s, accounting for about 43% of firstborns. Over half of women giving birth in Canada are now 30 or older, and about 22% are 35 or older. While most older mothers have uncomplicated pregnancies and deliver healthy babies, the risks associated with pregnancy do increase with age. Their babies are more likely to weigh less than 2.5 kilograms at birth, partly due to a higher incidence of multiple births among older mothers. Infants born to women over 35, regardless of whether it's a single or multiple birth, have a higher risk of issues like heart malformations and chromosomal disorders. Teenage mothers, compared to mothers in their 20s, have higher rates of congenital anomalies. Teenage pregnancy is linked to a higher risk of non-chromosomal congenital anomalies such as neural tube and central nervous system anomalies, gastrointestinal and female genitalia anomalies, and musculoskeletal/integumental anomalies like cleft lip/palate and club foot. However, teenage mothers in Canada are less likely to receive adequate prenatal care, maintain a healthy diet, have sufficient multivitamin and folic acid intake, and avoid exposure to smoke, alcohol, and drugs. They are more likely to experience mood disorders, sexually transmitted infections, and partner abuse. These factors make it challenging to identify the causal factors but highlight the need for improved preventive measures to mitigate negative outcomes for both mother and baby due to lifestyle factors. **Chronic Illnesses** Conditions like heart disease, diabetes, obesity, lupus, hormone imbalances, and epilepsy can negatively impact prenatal development. The emerging field of fetal-maternal medicine aims to manage pregnancies in women with these conditions to ensure the health of both mother and fetus. For instance, pregnancy can disrupt a diabetic woman's blood sugar control, potentially damaging the fetus's nervous system or causing rapid growth. To prevent this, fetal-maternal specialists must find a diet, medication, or a combination that stabilizes the mother's blood sugar without harming the fetus. Similarly, these specialists assist women with epilepsy in balancing their need for antiepileptic medication against potential fetal harm. **Maternal Mental Health** Psychologists suggest that a mother's emotions can impact prenatal development. Fetuses of mothers experiencing severe distress, such as anxiety or depression, are more likely to develop emotional, cognitive, or behavioral disorders in childhood and adulthood. This is believed to be due to changes in body chemistry caused by these stressful states, leading to differences in hormones and other chemicals that can affect the fetus. Some studies associate maternal stress hormones with reduced fetal growth rates. However, it's unclear whether this is a direct result of emotion-related hormones or an indirect effect of the mother's emotional state. For instance, a stressed or depressed mother might eat less or have a weakened immune system, both of which could hinder fetal growth. Providing social support and counseling to stressed and at-risk pregnant women can improve prenatal and infant health and development, particularly in high-risk families. **Teratogens: Mutagenic, Environmental, and Epimutagenic** Currently, teratogens fall within three broad categories: mutagenic, environmental, and unknown (Brent, 2004a; Hill, 2018). The unknown category is mostly composed of epigenetic factors and a single teratogen may fit more than one category. **Mutagenic Teratogens** Mutagens, a type of teratogens, can cause alterations to genomic DNA. Exposure to mutagens like radiation or biological or chemical toxins can lead to germinal mutations, affecting conception and the normal development of the embryo and fetus. For instance, if gametes are exposed to high levels of X-rays, it can result in infertility, or if conception occurs, the resulting genetic mutation can lead to implantation failure or miscarriage. In some cases, embryos exposed to mutagens may develop somatic mutations, which are chromosomal or genetic errors that can cause congenital anomalies and can be passed on to future generations. **Environmental Teratogens** Environmental agents can directly impact prenatal development by damaging cells or disrupting their normal development. These agents can interfere with cell proliferation in the embryo, affecting the formation of specific body tissues like neurons, muscles, and bones. They can also disrupt cell migration, which is the movement of differentiated cells to their genetically predetermined locations. For instance, this can occur when neural cells migrate along glial cells to their proper location in the brain. Additionally, these agents can cause structural and functional abnormalities in cells, such as when damaged neurons disrupt neural networks in the brain. For many Indigenous peoples living on reserves, pollutants found in traditional food sources can be directly transmitted through the environment. Pregnant Indigenous women are particularly concerned about the transfer of heavy metals like mercury, cadmium, arsenic, and lead to the fetus. Prenatal exposure to these pollutants can lead to preterm birth, low birth weight, and small for gestational age infants, who are at a higher risk of morbidity and multiple adult diseases, including cardiovascular diseases, diabetes, and cancers. Specifically, high levels of mercury and lead can impair neurocognitive development in fetuses and children. The dietary intake of these metals by Indigenous people living on reserves in Canada exceeds the national consumption guideline levels. **Epimutagenic Teratogens** Mutagens causing direct cell damage account for about 15 to 25% of congenital anomalies, and environmental factors account for another 10%. This leaves around two-thirds unaccounted for, with scientists suspecting that a large proportion of these "unknown" factors may be epigenetic. Epimutagens cause alterations to the epigenome (epimutations) without changing the genomic DNA. These epimutations, influenced by genetic, ecological, and even social and cultural factors, are usually limited to one generation as they're typically reset after conception. However, there are instances where acquired epimutations can be passed on to subsequent generations. For example, a parent's diet can cause enduring changes in successive generations, independent of their own dietary changes. This suggests that our current dietary habits could impact future generations through epimutagenic processes. Most human epigenetic research is currently based on epidemiological and demographic studies, but the hope is to discover precise molecular epigenetic mechanisms that underlie human health, disease, and longevity, leading to effective interventions, therapies, and preventions for current and future generations. **Paternal Influences: Preconceptual and Prenatal** Recent research has highlighted the father's role in reproductive risk, finding that fathers, on average, pass on about 55 genetic mutations to their children, compared to a mother's 14. The production, abnormalities, or performance of sperm can contribute to conditions like infertility, decreased fertility, and miscarriage. Additionally, DNA damage to sperm has been linked to conditions in offspring such as congenital anomalies, childhood cancer, and neurobehavioral disorders. Genetic and epigenetic effects significantly impact prenatal development, particularly during the first two trimesters. Contamination can occur through toxins in seminal fluids or indirect exposure to toxic agents from work clothes, shoes, and equipment. Higher reproductive risks are associated with men in specific occupations, such as janitors, painters, printers, firefighters, woodworkers, and those in agriculture, arts, and textile industries. This risk is suspected to be due to exposure to toxic substances like heavy metals, solvents, wood preservatives, pesticides, hydrocarbons, and radiation. Sperm affected by these factors up to two to three months before conception can impact prenatal development. Concerns are growing over the potential impact of fathers-to-be's unhealthy lifestyles and adverse experiences on their offspring, including factors like poor diet, obesity, smoking, alcohol intake, exposure to toxins, early-life traumas, and ongoing psychosocial stress. Current research suggests that paternal epimutagenic changes can be passed on to future generations. The father's age has been linked to adverse birth outcomes and congenital anomalies. Both teenage fathers and those in their 40s or older are associated with these risks. The average age of Canadian fathers at the birth of their first biological child has risen to over 28 years, raising concerns. A study of Icelandic families found that fathers pass on exponentially more mutations as they age, doubling every 16.5 years from puberty, while a mother's contribution of mutations remains relatively constant regardless of her age. Notably, an increase in paternal age is associated with a higher incidence of disorders such as autism and schizophrenia in offspring. Physical abuse during pregnancy is a significant threat to maternal and child health, leading to complications like premature labor, premature detachment of the placenta, and low birth weight. The prevalence of physical abuse increases during pregnancy, affecting approximately 6% of pregnant women in Canada. Almost two-thirds of this violence is perpetrated by the woman's husband, boyfriend, or ex-husband. Preventive measures could include screening newly pregnant women or those planning to conceive for potential abuse, along with addressing other lifestyle risk factors such as lack of paternal care and support, exposure to second-hand smoke, and unhealthy nutrition during pregnancy. **Fetal Assessment and Treatment** Genetic testing during pregnancy presents several concerns. These include medical risks for both the mother and the fetus, intense emotional and social impacts on the mother and family members as they contemplate actions based on test results, and privacy and confidentiality issues related to how genetic test results can affect insurability, employment, and social interactions. Since 2017, Canada's Genetic Non-Discrimination Act provides legal protection against discrimination based on genetic information in areas like insurance, employment, and human rights. Genetic counsellors can help women at risk of having a child with a congenital anomaly understand potential outcomes and choices. Preconception and first-trimester screening procedures assess the potential for developmental complications and determine if prenatal diagnostic testing is needed or desired. If diagnostic tests detect abnormalities, a genetics counsellor can help the mother and her family make informed decisions about her options. Ultrasonography, which monitors fetal growth by producing images from sound wave echoes, is a standard part of prenatal care in Canada. Other tests like chorionic villus sampling (CVS) and amniocentesis can identify chromosomal errors and genetic disorders before birth. CVS involves extracting cells from the placenta for laboratory tests during early prenatal development. Amniocentesis, performed between weeks 14 and 16 of pregnancy, involves extracting amniotic fluid containing fetal cells, which are then tested to diagnose chromosomal and genetic disorders. CVS is often used when a mother's medical condition requires early diagnosis of fetal abnormalities. Generally, amniocentesis has a lower risk of miscarriage and fetal injury than CVS, making it the preferred prenatal diagnostic technique. It's routinely recommended as a screening tool for Down syndrome and other chromosomal disorders in pregnant women over age 35. Various laboratory tests using maternal blood, urine, and amniotic fluid samples are used to monitor fetal development. The presence of alpha-fetoprotein in a pregnant woman's blood can indicate prenatal anomalies, including brain and spinal cord abnormalities. Additionally, a laboratory test can assess the maturity of fetal lungs, which is crucial when early delivery is advised due to the mother's health. Fetoscopy is a procedure that involves inserting a small camera into the womb to directly observe fetal development. This technique allows doctors to surgically correct certain anomalies and perform procedures like fetal blood transfusions and bone marrow transplants. Fetoscopy is also used to collect blood samples from the umbilical cord. These samples can be tested in a lab to assess fetal organ function, diagnose genetic and chromosomal disorders, and detect fetal infections. For instance, fetal blood tests can help identify a bacterial infection slowing fetal growth. Once diagnosed, the infection can be treated by injecting antibiotics into the amniotic fluid, which the fetus will swallow, or directly into the umbilical cord. **Birth and the Neonate** Once gestation is complete, the fetus must be born---an event that holds some pain for the mother as well as a good deal of joy for most parents. **Birth Choices** Traditionally, childbirth practices are determined by cultural norms. However, in modern Canada, parents have the flexibility to choose various aspects of their childbirth experience. This includes deciding who will be present during the birth, whether to use medication for pain management during labour and delivery, and the location of the birth. **The Location of Birth** Canadian parents can choose from several childbirth settings: a traditional hospital maternity unit, a hospital-based birth centre that offers a homelike environment and allows family presence, a standalone birth centre attended primarily by midwives or a physician, or the comfort of their own home. In Canada, most births (\~97.8%) occur in hospitals. Home deliveries are considered suitable for uncomplicated pregnancies with adequate prenatal care. Provided a trained birth attendant is present, the complication rate for home deliveries is comparable to that of hospital deliveries. **Midwives** Midwifery, a regulated healthcare profession in most parts of Canada, involves the care of women before, during, and after pregnancy. Midwives are licensed to oversee deliveries and care for newborns. To become a midwife in Canada, graduation from a recognized midwifery education program is required. **Drugs During Labour and Delivery** Expectant mothers have choices regarding the use of drugs during labour and delivery. Analgesics can alleviate pain, while sedatives or tranquilizers can lessen anxiety. Anaesthesia, often administered later in labour, can block pain either entirely or in specific body areas. An epidural, a type of local anaesthesia, can reduce the mother's pushing strength, slow the birthing process, and potentially necessitate additional medical procedures like an episiotomy or the use of vacuum suction or forceps. These interventions can increase complication risks and may delay early mother-baby contact. Researching the effects of labor drugs on a baby's behavior or development is challenging. Most drugs administered during labor cross the placenta, enter the fetal bloodstream, and can linger for days. Consequently, babies born to mothers who received any type of drug during labor are often slightly more lethargic, have breastfeeding difficulties, gain less weight, and sleep more in the initial weeks. There are limited well-controlled studies on the long-term effects of analgesics and tranquilizers. The key advice is for new mothers who received medication during childbirth to remember that their baby is also affected by these drugs, which can influence the baby's behavior in the first few days. Understanding this effect and knowing it will wear off can help maintain a healthy long-term mother-child relationship. Despite this, many women opt for natural childbirth, often using the Lamaze method in Canada. This approach involves selecting a labor coach, attending childbirth classes for psychological preparation, and learning techniques like using the term 'contraction' instead of 'pain'. The belief that natural childbirth benefits the baby motivates the mother to endure labor without pain-relieving medication. Relaxation and breathing techniques help manage the discomfort of contractions. **The Physical Process of Birth** Labour is generally divided into three stages. The first stage involves two key processes: dilation and effacement of the cervix, the opening at the bottom of the uterus. During this stage, the cervix must dilate, like a camera lens opening, and flatten out (effacement). By the time of delivery, the cervix typically dilates to about 10 centimetres. Stage 1 of labor is traditionally divided into phases. The early or latent phase features infrequent and typically mild contractions. The active phase begins when the cervix dilates to 3-4 centimetres and continues until it reaches 8 centimetres, with contractions becoming more frequent and intense. The final two centimetres of dilation occur during the transition phase, which is often the most painful due to closely spaced, strong contractions. However, the transition phase is usually the shortest. ![](media/image6.png)Figure 3.6 illustrates the average durations of different phases of labor for both first-time and subsequent births. However, it doesn't capture the significant individual differences that can occur. For instance, the first stage of labor in women giving birth to their first child can vary greatly, lasting anywhere from 3 to 20 hours. This highlights the wide range of experiences women can have during childbirth. After the transition phase of labor, mothers usually feel the urge to push to aid the baby's emergence. Once the cervix is fully dilated, the birth attendant encourages this pushing, marking the start of stage 2, the actual delivery. The baby's head moves past the cervix, through the birth canal, and out of the mother's body. This stage is often less distressing for women as they can actively participate in the delivery by pushing. Stage 2 typically lasts under an hour and seldom exceeds two hours. The brief stage 3 involves the delivery of the placenta and other uterine material. **Caesarean Deliveries** Most babies are delivered headfirst, facing the mother's spine. However, about 3% of babies are in different positions, such as feet or bottom first (breech presentations). In Canada, breech babies are usually delivered via Caesarean section (C-section) instead of vaginally. Performing a C-section before labor begins significantly reduces infant mortality and morbidity compared to vaginal delivery or a C-section after labor starts. C-sections are also recommended in cases of fetal distress, stalled labor, a large fetus, or maternal health conditions that could worsen with vaginal delivery or pose risks to the baby. Therefore, C-sections can prevent complications and save lives in many situations. While most doctors agree that a Caesarean section is necessary in some cases, the procedure is somewhat controversial. Critics argue that it's often performed unnecessarily, leading to potential complications such as excessive blood loss, blood clots, and infection, as well as increased healthcare costs. In the late 1960s, only about 5% of babies in Canada were delivered by C-section, but by 2001, this figure had risen to over 21%, one of the highest rates globally. The Society of Obstetricians and Gynaecologists of Canada does not endorse elective C-sections and recommends that the decision be based on an informed discussion of the risks and benefits between a woman and her doctor. **Birth Complications** During childbirth, some babies may experience fetal distress, indicated by a sudden change in heart rate. The cause of this distress is often unknown, but it can be due to pressure on the umbilical cord. If the cord gets trapped between the baby's head and the cervix, contractions can cause the blood vessels in the cord to collapse, preventing blood flow to the baby. This leads to anoxia, or oxygen deprivation, which can cause death or brain damage. However, quick surgical intervention, such as a Caesarean section, can prevent long-term effects. During birth, infants may experience complications such as dislocated shoulders or hips, fractures, or temporary facial paralysis due to nerve compression. These issues are typically not severe and resolve with minimal or no treatment. If a woman's blood pressure fluctuates significantly during labor, or if labor progresses too slowly (remaining in stage 1 for over 24 hours), a Caesarean section may be necessary. This can occur if the baby's head position prevents sufficient pressure on the cervix for dilation. Continuing labor in such cases could cause permanent damage to the mother's body. Postpartum, women typically need about a month to recover. This period involves various hormonal changes necessary for breastfeeding and resumption of the menstrual cycle. Some women may experience postpartum depression. However, most women recover quickly, both physically and emotionally, from pregnancy and childbirth. **Assessing the Neonate** In the first month of life, a baby is known as a neonate. The Apgar scale, established in 1953, is commonly used to assess the health of newborns in hospitals, birthing centres, and home births attended by professional midwives. The baby is scored from 0 to 2 on five different criteria. A perfect score of 10 is rare immediately after birth due to most infants having some blueness in their fingers and toes. However, 85 to 90% of infants score 9 or 10 at a second assessment, typically five minutes after birth. A score of 7 or above is considered safe, while a score of 4 to 6 indicates the baby may need assistance with breathing. A score of 3 or below signifies a critical condition. Standard screening procedures in Canada now include the detection of rare metabolic disorders in newborns, thanks to the introduction of new tandem mass spectrometry technology. This technology can efficiently and cost-effectively run multiple tests simultaneously, allowing for the presymptomatic detection of inborn metabolic anomalies. Early detection enables early treatment, leading to improved outcomes for infants and their families. The Brazelton Neonatal Behavioral Assessment Scale is commonly used by health professionals to monitor a newborn's development during the first couple of weeks after birth. This assessment includes the neonate's responses to stimuli, reflexes, muscle tone, alertness, cuddliness, and self-soothing ability. The scores from this test can help identify children who may have significant neurological problems. **Low Birth Weight** The weight classification of a neonate is a crucial part of their assessment. Neonates weighing less than 2500 grams are categorized as having low birth weight (LBW). In Canada, the percentage of LBW infants has been gradually increasing over the past few decades, currently accounting for approximately 6.4% of all newborns. LBW infants have higher hospitalization rates and an increased incidence of illness and mortality. Most low birth weight (LBW) infants are preterm, meaning they are born before the 38th week of gestation. However, it's possible for a baby to complete 38 or more weeks of gestation and still be classified as LBW. Some preterm babies have a weight appropriate for their gestational age, while others are smaller than expected. These small-for-date neonates, who seem to have experienced slowed fetal growth, generally have poorer prognoses compared to infants with weights appropriate for their gestational age. Low birth weight (LBW) infants show significantly less responsiveness at birth and during early life compared to other infants. Infants born more than 6 weeks prematurely often suffer from respiratory distress syndrome (also known as hyaline membrane disease), which is characterized by severe breathing difficulties due to underdeveloped lungs. In 1990, a treatment was introduced where surfactant, a chemical facilitating oxygen and carbon dioxide exchange in the blood, was administered to preterm neonates. This therapy has successfully decreased the mortality rate among very-low-birth-weight infants. Most low birth weight (LBW) babies weighing over 1500 grams catch up to their peers within the first few years of life, though at varying rates. However, those weighing less than 1500 grams remain smaller and have higher rates of neonatal and long-term health issues, including motor and sensory impairment, lower intelligence test scores, and school problems. Boys are more susceptible to the long-term effects of low birth weight. A study of over 700 six-year-olds found a higher rate of learning disabilities and other issues in LBW boys compared to their normal-birth-weight peers. Interestingly, LBW girls showed no differences from their normal-birth-weight counterparts. The disparity between LBW and normal-birth-weight boys persisted into age 11. Addressing socioeconomic disparities could help reduce low birth weight (LBW) rates among low-income, at-risk mothers. A review of programs in Manitoba aimed at improving pregnancy outcomes found that providing unconditional prenatal income to the lowest income women led to positive results. These included reductions in LBW, preterm births, and hospital stay lengths, as well as increased initiation of breastfeeding. **Policy Question** **What Legal Protection Exists for the Pregnant Mother and Her Fetus?** Society has established laws to safeguard individual rights and outline penalties for violations. In the context of a pregnant woman and her fetus, the aim is to protect the interests of both. However, due to their intrinsic relationship, conflicts between their respective needs can pose legal dilemmas. While the physical relationship between mother and fetus is clear, defining this relationship in legal terms often results in an imperfect representation. Canadian law, which does not recognize a fetus as a human being, does not classify the termination of a fetus as homicide or infanticide. This perspective, rooted in common law, was incorporated into the first Canadian Criminal Code of 1892, and continues today. Laws against procuring a miscarriage were established, and in 1969, Section 287 made abortions illegal, with exceptions for doctors if a mother's health or life was at risk. In 1982, the Canadian Charter of Rights and Freedoms declared everyone's right to life, liberty, and security. Around the same time, Henry Morgentaler challenged the abortion law by establishing non-hospital abortion clinics. In 1988, the Supreme Court of Canada ruled that the abortion law violated Section 7 of the Charter, as it interfered with a woman's body and liberty. This led to the modification of Section 287, effectively decriminalizing abortions and implying that a fetus is not protected under the Charter. Consequently, abortions at any stage of pregnancy are not prohibited in Canada. By the end of the 20th century, legal dilemmas arose concerning the rights of a pregnant woman versus the well-being of her fetus. Three court cases highlight these challenges. One case involved Winnipeg Child Family Services and a pregnant woman addicted to glue sniffing, which can cause permanent damage to the fetus. The agency aimed to detain her for treatment until childbirth, but this was deemed a violation of the mother's rights. The case reached the Supreme Court of Canada in 1997, which ruled in favor of the mother's rights over the fetus's, based on the Charter of Rights and Freedoms. This decision raised concerns about potential scrutiny and incarceration of pregnant women for lifestyle choices that could harm the fetus, leading to questions about who sets the standard for maternal behavior. The judgment reaffirmed that a fetus has no legal rights, though it retains a moral right to be treated well. The Dobson v. Dobson case involved a pregnant woman who had a car accident at 27 weeks of pregnancy, resulting in her child having permanent mental and physical issues. The child's grandfather sued the mother for negligence. Legal precedent allows a child born alive to take legal action against a third party for prenatal injuries, as seen in cases of thalidomide-induced congenital anomalies. The courts had to decide if the mother could be sued as a third party. The New Brunswick Courts ruled in favor of the boy's compensation. However, this ruling was overturned by the Supreme Court in 1999, emphasizing the unique relationship between a mother and her fetus. The statement suggests that the relationship between a mother and her fetus is unique and inseparable until birth. This means that the mother's actions cannot be compared to those of a third party when it comes to potential harm to the fetus. The mother and fetus are considered as one entity, and any harm to the fetus is not viewed in the same way as harm inflicted by an external party. Additionally, the statement highlights the challenge of defining a standard of care that a pregnant mother should adhere to for her fetus. Any attempt to establish such a standard could infringe on the mother's privacy and autonomy. It's a delicate balance between ensuring the well-being of the fetus and respecting the rights and freedoms of the mother. This underscores the complexity of legal and ethical issues surrounding pregnancy and fetal rights. Brenda Drummond, an Ontario woman, was initially charged with attempted murder after she shot a pellet into her full-term fetus's head. The boy was born two days later, and his health critically deteriorated until a brain scan revealed the pellet, which was then surgically removed. The mother didn't disclose the incident until after the operation. In court, the judge ruled that the fetus couldn't be considered a separate victim from its mother at the time of the shooting, leading to the dismissal of the case as the fetus has no separate legal rights. However, Drummond was later charged with failing to provide the necessities of life for her newborn when she didn't inform doctors about the shooting, endangering his health. She pleaded guilty to this charge and received a suspended sentence. **List of Key Terms** **Amnion:** fluid-filled sac in which the fetus floats until just before it is born. **Anoxia:** oxygen deprivation experienced by a fetus during labour and/or delivery. **assisted human reproduction (AHR):** "any activity undertaken for the purpose of facilitating human reproduction" Health Canada. (2001a). **axons**: tail-like extensions of neurons. **body mass index (BMI)**: a ratio of weight to height that estimates healthy and unhealthy body composition. **Caesarean section (C-section)**: delivery of an infant through incisions in the abdominal and uterine walls. **cell bodies**: the part of a neuron that contains the nucleus and is the site of vital cell functions. **cell migration**: the movement of cells to their genetically predetermined destinations in the body **cell proliferation**: the increase in cell numbers by means of cell growth and cell division. **cephalocaudal pattern**: growth that proceeds from the head downward. **congenital anomaly**: an abnormality presents at birth. **cryopreservation**: preserving cells or tissues through a freezing process that stops all biological activity. **Dendrites**: branch-like protrusions from the cell bodies of neurons **embryonic stage**: the second stage of prenatal development, from week 2 through week 8, during which the embryo's organ systems form. **Epimutagens**: agents that cause abnormal gene silencing or expression without changing the genomic DNA. **fetal stage**: the third stage of prenatal development, from week 9 to birth, during which growth and organ refinement take place. **Gametes**: cells that unite at conception (ova in females; sperm in males). **germinal stage**: the first stage of prenatal development, beginning at conception and ending at implantation (approximately two weeks). **glial cells**: specialized cells in the brain that support neurons. **Gonads**: sex glands (ovaries in females; testes in males). **Implantation**: attachment of the blastocyst to the uterine wall. **low birth weight (LBW)**: newborn weight below 2500 grams. **Microcephaly**: a condition characterized by incomplete brain development and a smaller-than-expected head circumference, which can lead to neurological disorders such as intellectual disabilities and delays in motor and sensory development. **Mutagens**: agents that cause changes (mutations) in genomic DNA. **Neonate**: baby between birth and 1 month of age. **Neurons**: specialized cells of the nervous system. **neurobehavioural disorders**: cognitive and behavioural disorders that are associated with brain dysfunction, such as autism spectrum disorder, ADHD, and dyslexia. **Neurotransmitters**: chemical messengers that travel across the synapses and enable neurons to communicate with other neurons. **Organogenesis**: process of organ development. **Placenta**: specialized organ that allows substances to be transferred from mother to embryo and from embryo to mother without their blood mixing. **proximodistal pattern**: growth that proceeds from the middle of the body outward. **respiratory distress syndrome**: a disease in which poorly developed lungs of infants cause serious breathing difficulties. **Synapses**: tiny spaces across which neural impulses flow from one neuron to the next. **umbilical cord**: organ that connects the embryo to the placenta. **Viability**: ability of the fetus to survive outside the womb. **Vitrification:** the use of cryoprotectants along with rapid cooling to prevent the fluid in biological tissues (e.g., eggs, semen, embryos) from forming ice crystals (which act like glass shards on cell structures) and from dehydrating; the tissue becomes an intact, non-crystalline, glass-like solid that can be preserved for years. **Zygote**: a single cell created when sperm and ovum unite.

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