WEEK 4_ FETAL GROWTH AND DEVELOPMENT.pdf

WEEK 4: FETAL GROWTH AND DEVELOPMENT NCMA 217 - Maternal and Child Health Nursing (LECTURE) 2ND YEAR - BS NURSING | FIRST SEM (PRELIMS) which is why, at birth, the entire inner surface of OUTLINE...

WEEK 4: FETAL GROWTH AND DEVELOPMENT NCMA 217 - Maternal and Child Health Nursing (LECTURE) 2ND YEAR - BS NURSING | FIRST SEM (PRELIMS) which is why, at birth, the entire inner surface of OUTLINE the uterus is stripped away, leaving the organ 1. Embryonic Structure and Fetal Structures highly susceptible to hemorrhage and infection a. The Decidua After fertilization, the corpus luteum in the ovary b. Chorionic Villi continues to function rather than atrophying, c. The Amniotic Membranes because of the influence of human chorionic d. The Amniotic Fluid gonadotropin (hCG), a hormone secreted by the e. The Umbilical Cord trophoblast cells. 2. Fetal Development This causes the uterine endometrium to continue 2.1. Origin of Organ Systems to grow in thickness and vascularity, instead of 3. Milestones of Fetal Growth and Development sloughing off as in a usual menstrual cycle. 3.1. First Trimester (Period of Organogenesis Most Critical) The endometrium is now termed the decidua (the 3.2. Second Trimester (Period of Continuous Latin word for “falling off”), because it will be Growth & Development) discarded after the birth of the child. 3.3. Third Trimester (Period of Most Rapid Growth) B. Chorionic Villi 3.3.1. Fetal Circulation Once implantation is complete, the trophoblast layer of cells of the blastocyst begins to mature 1. Embryonic Structure and Fetal Structures rapidly. As early as the 11th or 12th day, miniature villi that resemble probing fingers, termed chorionic villi, reach out from the single A. The Decidua layer of cells into the uterine endometrium to Term used for the thick vascular endometrium begin formation of the placenta. At term, almost after implantation 200 such villi will have formed (Knuppel, 2007). The decidua has three separate areas: All chorionic villi have a central core of connective tissue and fetal capillaries. A double layer of trophoblast cells surrounds these. The outer of the two covering layers is the syncytiotrophoblast,or the syncytial layer. This layer of cells produces various placental hormones, such as hCG, somatomammotropin (human placental lactogen [hPL]), estrogen, and progesterone. The middle layer, the cytotrophoblast or Langhans’ layer, is present as early as 12 days’ gestation. It appears to function early in pregnancy to protect the growing embryo and fetus from certain infectious organisms such as the spirochete of syphilis. This layer of cells disappears, however, between the 20th and 24th 1. Decidua basalis, the part of the endometrium weeks. This is why syphilis is not considered to that lies directly under the embryo (or the portion have a high potential for fetal damage early in where the trophoblast cells establish pregnancy, only after the point at which communication with maternal blood vessels) cytotrophoblast cells are no longer present 2. Decidua capsularis, the portion of the (Ainbinder, Ramin, & DeCherney, 2007). The endometrium that stretches or encapsulates the layer appears to offer little protection against viral surface of the trophoblast invasion at any point. 3. Decidua vera, the remaining portion of the uterine lining. As the embryo continues to grow, it pushes the decidua capsularis before it like a blanket. Eventually, the embryo enlarges so much that this action brings the decidua capsularis into contact with the opposite uterine wall (the decidua vera). Here, the two decidua areas fuse,  mother during pregnancy. Because the outer chorionic villi layer is only one cell thick after the third trimester minute breaks do occur and allow occasional fetal cells to cross into the maternal bloodstream, as well as fetal enzymes such as alpha-fetoprotein (AFP) from the fetal liver. About 100 maternal uterine arteries supply the mature placenta. To provide enough blood for exchange, the rate of uteroplacental blood flow in pregnancy increases from about 50 mL/min at 10 weeks to 500 to 600 mL/min at term. The woman’s heart rate, total cardiac output, and blood volume increase to supply blood to the placenta Uterine perfusion, and thus placental circulation, is most efficient when the woman lies on her left side. This position lifts the uterus away from the inferior vena cava, preventing blood from being trapped in the woman’s lower extremities. If the woman lies on her back and the weight of the uterus compresses the vena cava, placental circulation can be so sharply reduced that supine hypotension (very low maternal blood pressure and poor uterine circulation) occurs (Knuppel, 2007). At term, the placental circulatory network has grown so extensively that a placenta weighs 400 The Placenta to 600 g (1 lb), onesixth the weight of the baby. If The placenta (Latin for “pancake,” which is a placenta is smaller than this, it suggests that descriptive of its size and appearance at term) circulation to the fetus may have been arises out of the continuing growth of trophoblast inadequate. A placenta larger than this may also tissue. indicate that circulation to the fetus was Its growth parallels that of the fetus, growing from threatened, because it suggests that the placenta a few identifiable cells at the beginning of was forced to spread out in an unusual manner pregnancy to an organ 15 to 20 cm in diameter to maintain a sufficient blood supply. The fetus of and 2 to 3 cm in depth, covering about half the a woman with diabetes may also develop a surface area of the internal uterus at term. larger-than-usual placenta from excess fluid collected between cells. Circulation As early as the 12th day of pregnancy, maternal Endocrine Function blood begins to collect in the intervillous spaces Aside from serving as the conduit for oxygen and of the uterine endometrium surrounding the nutrients for the fetus, the syncytial (outer) layer chorionic villi. By the third week, oxygen and of the chorionic villi develops into a separate, other nutrients, such as glucose, amino acids, important hormone-producing system. fatty acids, minerals, vitamins, and water, osmose from the maternal blood through the cell 1. Human Chorionic Gonadotropin. layers of the chorionic villi into the villi capillaries. ○ The first placental hormone produced, From there, nutrients are transported to the hCG, can be found in maternal blood developing embryo. and urine as early as the first missed Placental osmosis is so effective that all except a menstrual period (shortly after few substances are able to cross from the implantation has occurred) through mother into the fetus. Because almost all drugs about the 100th day of pregnancy. are able to cross into the fetal circulation, it is ○ Because this is the hormone analyzed important that a woman take no nonessential by pregnancy tests, a false-negative drugs (including alcohol and nicotine) during result from a pregnancy test may be pregnancy (Rogers-Adkinson & Stuart, 2007). obtained before or after this period. For practical purposes, because the process of ○ The woman’s blood serum will be osmosis is so effective, there is no direct completely negative forhCG within 1 to 2 exchange of blood between the embryo and the weeks after birth. Testing for hCG after BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 2  birth can be used as proof that placental of these nutrients are always available to tissue is no longer present. the fetus (Taylor & Lebovic, 2007). ○ The purpose of hCG is to act as a fail-safe measure to ensure that the Placental proteins corpus luteum of the ovary continues to The placenta also produces several plasma produce progesterone and estrogen. proteins. The function of these has not been well ○ This is important because, if the corpus documented, but it is thought that they may luteum should fail and the level of contribute to decreasing the immunologic impact progesterone fall, the endometrial lining of the growing placenta through being part of the will slough and the pregnancy will be complement cascade (Knuppel, 2007). lost. hCG also may play a role in suppressing the maternal immunologic C. The Amniotic Membranes response so that placental tissue is not detected and rejected as a foreign substance. 2. Estrogen ○ Estrogen (primarily estriol) is produced as a second product of the syncytial cells of the placenta. ○ Estrogen contributes to the woman’s mammary gland development in preparation for lactation and stimulates uterine growth to accommodate the developing fetus. 3. Progesterone ○ Estrogen is often referred to as the Chorionic Membrane Amniotic Membrane “hormone of women”; progesterone as Outermost fetal Second the “hormone of mothers.” membrane membrane / ○ This is because, although estrogen Purpose: to form inner lining influences a female appearance, the sac that Purpose: progesterone is necessary to maintain contains the Produces the endometrial lining of the uterus amniotic fluid/ to amniotic fluid during pregnancy. support the and produces ○ It is present in serum as early as the amniotic fluid phospholipids fourth week of pregnancy, as a result of that initiates the the continuation of the corpus luteum. release of After placental synthesis begins (at prostaglandins about the 12th week), the level of which can cause progesterone rises progressively during uterine the remainder of the pregnancy. contractions and ○ This hormone also appears to reduce may be trigger the contractility of the uterus during that initiates pregnancy, preventing premature labor. labor 4. Human Placental Lactogen (Human Chorionic Somatomammotropin). ○ hPL is a hormone with both The chorionic villi on the medial surface of the growth-promoting and lactogenic trophoblast (those that are not involved in (milk-producing) properties. implantation, because they do not touch the ○ It is produced by the placenta beginning endometrium) gradually thin, leaving the medial as early as the sixth week of pregnancy, surface of the structure smooth (the chorion increasing to a peak level at term. It can laeve, or smooth chorion). be assayed in both maternal serum and The smooth chorion eventually becomes the urine. chorionic membrane, the outermost fetal ○ It promotes mammary gland (breast) membrane. Its purpose is to form the sac that growth in preparation for lactation in the contains the amniotic fluid. mother. A second membrane lining the chorionic ○ It also serves the important role of membrane, the amniotic membrane or amnion, regulating maternal glucose, protein, forms beneath the chorion. Early in pregnancy, and fat levels so that adequate amounts these membranes become so adherent that they BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 3  seem as one at term. At birth they can be seen The most important purpose of amniotic fluid is covering the fetal surface of the placenta, giving to shield the fetus against pressure or a blow that surface its typically shiny appearance. There to the mother’s abdomen. Because liquid is no nerve supply, so when they spontaneously changes temperature more slowly than air, it also rupture at term or are artificially ruptured, neither protects the fetus from changes in temperature. woman nor child experiences any pain. As yet another function, it aids in muscular In contrast to the chorionic membrane, the development, because it allows the fetus amniotic membrane not only offers support to freedom to move. Finally, it protects the umbilical amniotic fluid but also actually produces the fluid. cord from pressure, protecting the fetal oxygen In addition, it produces a phospholipid that supply. Even if the amniotic membranes rupture initiates the formation of prostaglandins, which before birth and the bulk of amniotic fluid is lost, can cause uterine contractions and maybe the some will always surround the fetus in utero, trigger that initiates labor because new fluid is constantly formed. Amniotic fluid is slightly alkaline, with a pH of about 7.2. D. The Amniotic Fluid Checking the pH of the fluid at the time of rupture helps to differentiate it from urine, which is acidic (pH 5.0–5.5). IMPORTANT INFO Amniotic Fluid Alkaline fluid which is composed of 99% water and 1% solid particles containing albumin, urea, uric acid, creatinine, lecithin, sphingomyelin, bilirubin, and vernix caseosa Should be clear, colorless to straw-colored with tiny specks of vernix caseosa 800 – 1200 ml at term Amniotic fluid is constantly being newly formed Very important as it serves many functions and reabsorbed by the amniotic membrane, so it never becomes stagnant. Some of it is absorbed Functions of amniotic fluid by direct contact with the fetal surface of the Shock absorber placenta. ○ shield fetus against pressure or a The major method of absorption, however, blow to the mothers abdomen – occurs because the fetus continually swallows Thermoregulator the fluid. In the fetal intestine, it is absorbed into ○ because liquid changes temperature the fetal bloodstream. From there, it goes to the more slowly than air umbilical arteries and to the placenta, and it is Prevents compression of the cordprevents exchanged across the placenta. pressure, protecting the fetal oxygen supply At term, the amount of amniotic fluid has Aids in muscular development increased so much it ranges from 800 to 1200 ○ allows the fetus the freedom to move mL If for any reason the fetus is unable to swallow Normal (esophageal atresia or anencephaly are the two 800-1200 mL most common reasons), excessive amniotic fluid,or hydramnios(more than 2000 mL in total, More than 2000 ml or pockets of fluid larger than 8 cm on hydramnios may be due to DM excessive fluid ultrasound), will result. Hydramnios also tends to shifts into the amniotic space occur in women with diabetes, because hyperglycemia causes excessive fluid shifts into Less than 300ml oligohydramnios due to the amniotic space (Bush & Pernoll, 2007). disturbance of kidney function Color: Early in fetal life, as soon as the fetal kidneys Green - meconium stained become active, fetal urine adds to the quantity of Gray- infection the amniotic fluid. A disturbance of kidney Gold- Hemolytic disease (Rh Incompatibility) function may cause oligohydramnios, or a Brown – Fetal death reduction in the amount of amniotic fluid (less Bloody – vasa previa / abruptio placenta than 300 mLin total, or no pocket on ultrasound larger than 1 cm) (Knuppel, 2007). BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 4 E. The Umbilical Cord Ectoderm Mesoderm Endoderm The umbilical cord is formed from the fetal membranes (amnion and chorion) and Nervous system -Supporting -Lining of the provides a circulatory pathway that connects - Skin, hair, nails structures of the pericardial the embryo to the chorionic villi of the - Sebaceous body pleura placenta. glands -Dentin of teeth and peritoneal - Sense organs -Upper portion cavities Its function is to transport oxygen and - Mucous of Lining of the GI nutrients to the fetus from the placenta and to membranes of the urinary tract, respiratory return waste products from the fetus to the anus, mouth, system tract, tonsils, placenta. and -Reproductive parathyroid, It is about 53 cm (21 in) in length at term and nose system thyroid, about 2 cm (3 ⁄4 in) thick. - Tooth enamel -Cardiovascular thymus glands The bulk of the cord is a gelatinous - Mammary system -Lower urinary glands -Lymph vessels system mucopolysaccharide called Wharton’s jelly, which gives the cord body and prevents pressure on the vein and arteries that pass through it. The outer surface is covered with amniotic membrane. An umbilical cord contains only one vein (carrying blood from the placental villi to the fetus) but two arteries (carrying blood from the fetus back to the placental villi). The number of veins and arteries in the cord is always assessed and recorded at birth because about 1% to 5% of infants are born with a cord that contains only a single vein and artery. From 15% to 20% of these infants are found to have accompanying chromosomal disorders or congenital anomalies, particularly of the kidney and heart (Lubusky et al., 2007).Blood can be withdrawn from the umbilical vein or transfused At the time of implantation, a blastocyst already into the vein during intrauterine life for fetal has differentiated to a point at which two assessment or treatment (termed percutaneous separate cavities appear in the inner structure: umbilical blood sampling [PUBS]). (1) a large one, the amniotic cavity, which is In about 20% of all births, a loose loop of cord is lined with a distinctive layer of cells, the found around the fetal neck (nuchal cord) at birth. ectoderm, and (2) a smaller cavity, the yolk If this loop of cord is removed before the sac, which is lined with endoderm cells. newborn’s shoulders are born, so that there is no In humans, the yolk sac appears to supply traction on it, the oxygen supply to the fetus nourishment only until implantation. After that, its remains unimpaired (Jackson, Melvin, & Downe, main purpose is to provide a source of red blood 2007). Because the umbilical cord contains no cells until the embryo’s hematopoietic system is nerve supply, it can be cut at birth without mature enough to perform this function (at about discomfort to either the child or woman the 12th week of intrauterine life). The yolk sac then atrophies and remains only as a thin white 2. FETAL DEVELOPMENT streak discernible in the cord at birth. Between the amniotic cavity and the yolk sac, a third layer 2.1 Origin of Organ Systems of primary cells, the mesoderm, forms. The embryo will begin to develop at the point where the three cell layers (ectoderm, entoderm, and A. Primary germ layers mesoderm) meet, called the embryonic shield. Involved in organogenesis Each of these germ layers of primary tissue. Ectoderm, Mesoderm, Endoderm Knowing the origins of body structures helps to explain why certain screening procedures are ordered for newborns with congenital malformations. A radiographic examination of the kidney, for example, may be ordered for a child born with a heart defect. A child with a malformation of the urinary tract is often BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 5  investigated for reproductive abnormalities as II. End of 8th Gestational Week (8th week, 2nd well. month) All organ systems are complete, at least in a Length: 2.5 cm (1 in) rudimentary form, at 8 weeks’ gestation (the end Weight: 20 g of the embryonic period). During this early time of Organogenesis is complete. organogenesis (organ formation), the growing The heart, with a septum and valves, is beating structure is most vulnerable to invasion by rhythmically. teratogens (any factor that adversely affects the Facial features are definitely discernible. fertilized ovum, embryo, or fetus, such as Arms and legs have developed. cigarette smoking). External genitalia are forming, but sex is not yet distinguishable by simple observation. The primitive tail is regressing. 3. MILESTONES OF FETAL GROWTH AND The abdomen bulges forward because the fetal DEVELOPMENT intestine is growing so rapidly. An ultrasound shows a gestational sac, FIRST TRIMESTER diagnostic of pregnancy (Fig. 9.8). PERIOD OF ORGANOGENESIS MOST CRITICAL I. End of 4th Gestational Week (4th week, 1st Month) At the end of the fourth week of gestation, the human embryo is a group of rapidly growing cells but does not yet resemble a human being. Length: 0.75–1 cm Weight: 400 mg The spinal cord is formed and fused at the midpoint. Lateral wings that will form the body are folded forward to fuse at the midline. The head folds forward and becomes prominent, representing about one-third of the entire structure. The back is bent so that the head almost touches the tip of the tail. The rudimentary heart appears as a prominent bulge on the anterior surface. Arms and legs are budlike structures. Rudimentary eyes, ears, and nose are discernible. III. End of 12th Gestational Week (First Trimester) Length: 7–8 cm Weight: 45 g Nail beds are forming on fingers and toes. Spontaneous movements are possible, although they are usually too faint to be felt by the mother. Some reflexes, such as the Babinski reflex, are present. Bone ossification centers begin to form. Tooth buds are present. Sex is distinguishable by outward appearance. Urine secretion begins but may not yet be evident in amniotic fluid. The heartbeat is audible through Doppler technology. BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 6  SECOND TRIMESTER FOCUS: LENGTH OF FETUS I. End of 16th Gestational Week Length: 10–17 cm Weight: 55–120 g Fetal heart sounds are audible by an ordinary stethoscope. Lanugo is well formed Liver and pancreas are functioning. Fetus actively swallows amniotic fluid, demonstrating an intact but uncoordinated swallowing reflex; urine is present in amniotic fluid. Sex can be determined by ultrasound. III. End of 24th Gestational Week Length: 28–36 cm Weight: 550 g Meconium is present as far as the rectum Active production of lung surfactant begins. Eyebrows and eyelashes become well defined. Eyelids, previously fused since the 12th week, now open. Pupils are capable of reacting to light. When fetuses reach 24 weeks, or 601 g, they have achieved a practical low-end age of viability (earliest age at which fetuses could survive if born at that time), if they are cared for after birth II. End of 20th Gestational Week in a modern intensive care facility. Length: 25 cm Hearing can be demonstrated by response to Weight: 223 g sudden sound. Spontaneous fetal movements can be sensed by the mother. Antibody production is possible. The hair forms on the head, extending to include eyebrows. Meconium is present in the upper intestine. Brown fat, a special fat that will aid in temperature regulation at birth, begins to be formed behind the kidneys, sternum, and posterior neck. Vernix caseosa begins to form and cover the skin. Passive antibody transfer from mother to fetus begins. Definite sleeping and activity patterns are distinguishable (the fetus has developed biorhythms that will guide sleep/wake patterns throughout life). THIRD TRIMESTER Period of Most Rapid Growth FOCUS: Weight of Fetus I. End of 28th Gestational Week Length: 35–38 cm Weight: 1200 g Lung alveoli begin to mature, and surfactant can be demonstrated in amniotic fluid. BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 7  Testes begin to descend into the scrotal sac from Sole of the foot has only one or two crisscross the lower abdominal cavity. creases, compared with the full crisscross The blood vessels of the retina are formed but pattern that will be evident at term. thin and extremely susceptible to damage from Amount of lanugo begins to diminish. high oxygen concentrations (an important Most babies turn into a vertex (head down) consideration when caring for preterm infants presentation during this month. who need oxygen). II. End of 32nd Gestational Week IV. End of 40th Gestational Week (Third Length: 38–43 cm Trimester) Weight: 1600 g Length: 48–52 cm (crown to rump, 35–37 cm) Subcutaneous fat begins to be deposited (the Weight: 3000 g (7–7.5 lb) former stringy, “little old man” appearance is Fetus kicks actively, hard enough to cause the lost) mother considerable discomfort. Fetus responds by movement to sounds outside Fetal hemoglobin begins its conversion to adult the mother’s body. hemoglobin. The conversion is so rapid that at Active Moro reflex is present. birth, about 20% of hemoglobin will be adult in Iron stores, which provide iron for the time during character. which the neonate will ingest only milk after Vernix caseosa is fully formed. birth, are beginning to be developed. Fingernails extend over the fingertips. Fingernails grow to reach the end of fingertips. Creases on the soles of the feet cover at least two thirds of the surface III. End of 36th Gestational Week IMPORTANT INFO Length: 42–48 cm Weight: 1800–2700 g (5–6 lb) FETAL GROWTH AND DEVELOPMENT Body stores of glycogen, iron, carbohydrate, and 266-280 days (37-42 weeks) calcium are deposited. 280/28 = 10 lunar months Additional amounts of subcutaneous fat are 280/30 = 9.7 calendar months deposited. BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 8 FETAL CIRCULATION day, such as from sun rays), it causes no 1. As early as the third week of intrauterine life, fetal damage. However, in large doses (e.g., the blood begins to exchange nutrients with the amount of radiation necessary to treat cancer of maternal circulation across the chorionic villi. the cervix), serious fetal defects or death can Blood arriving from the placenta is highly occur oxygenated. The timing of the teratogenic insult makes a 2. Blood enters at the umbilical vein ( carries significant impact on damage done to the fetus. If oxygenated blood) because the direction of the a teratogen is introduced before implantation, blood is toward the fetal heart. either the zygote is destroyed or it appears 3. Special structures present in the fetus then shunt unaffected. If the insult occurs when the main blood flow to first supply the most important body systems are being formed (in the second to organs of the body. Brain, liver, heart and eighth weeks of embryonic life), a fetus is very kidneys. vulnerable to injury. During the last trimester, the 4. Blood flows from the umbilical vein going to potential for harm again decreases because all ductus venosus- an accessory vessel that directs the organs of a fetus are formed and are merely oxygenated blood directly to the fetal liver. maturing. 5. Then blood empties into the fetal inferior vena Two exceptions to the rule that deformities cava -- --so oxygenated blood is directed to the usually occur in early embryonic life are the right side of the heart 6 effects caused by the organisms of syphilis and 6. Enters Right atrium then going into left atrium toxoplasmosis. These two infections can cause through Foramen ovale. Then left atrium going to abnormalities in organs that were originally aorta formed normally. 7. Small amount of blood that returns to the heart A third factor determining the effects of a via the vena cava does leave the right atrium via teratogen is the teratogen’s affinity for specific the adult circulatory route then through tricuspid tissue. Lead and mercury, for example, attack valve into the right ventricle, and then into the and disable nervous tissue. Thalidomide, a drug pulmonary artery and lungs to service the lung once used to relieve nausea in pregnancy, tissue. However, the larger portion of even this causes limb defects. Tetracycline, a common blood is shunted away from the lungs through antibiotic, causes tooth enamel deficiencies and, ductus arteriosus directly into the descending possibly, long-bone deformities. The rubella virus aorta can affect many organs: the eyes, ears, heart, 8. Most blood flow from the Descending aorta is and brain are the four most commonly attacked. transported to umbilical arteries( called arteries though they are transporting deoxygenated Teratogenic Maternal Infections blood) they are carrying blood away from the 1. Toxoplasmosis fetal heart) back through umbilical cord going to ○ Toxoplasmosis, a protozoan infection, is placental villi where new oxygen takes place spread most commonly through contact with uncooked meat, although it may Preventing Fetal Exposure to Teratogens also be contracted through handling cat A teratogen is any factor, chemical or physical, stool in soil or cat litter (Friars, 2007). that adversely affects the fertilized ovum, ○ As many as 1 in 900 pregnancies may embryo, or fetus. At one time, it was assumed be affected by toxoplasmosis. that a fetus in utero was protected from chemical ○ A woman experiences almost no or physical injury by the presence of the amniotic symptoms of the disease except for a fluid and by the absence of any direct placental few days of malaise and posterior exchange between mother and fetus. When cervical lymphadenopathy. Even in light infants were born with disorders, it was attributed of these mild symptoms, to the influence of fate, bad luck, or, in some ○ If the infection crosses the placenta, the cultures, evil spirits. Today, it is acknowledged infant may be born with central nervous that a fetus is extremely vulnerable to system damage, hydrocephalus, environmental injury. microcephaly, intracerebral calcification, and retinal deformities. Effects of Teratogens on a Fetus ○ Pre Pregnancy serum analysis can be Several factors influence the amount of damage done to identify women who have never a teratogen can cause. The strength of the had the disease and so are susceptible teratogen is one of these. For example, radiation (about 50% of women). is a known teratogen. In small amounts ○ Instruct pregnant women to avoid (everyone is exposed to some radiation every undercooked meat and also not to BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 9  change a cat litter box or work in soil in microcephaly, spasticity) or with eye damage an area where cats may defecate to (optic atrophy, chorioretinitis), hearing avoid exposure to the disease. impairment, or chronic liver disease. The child’s ○ If the diagnosis is established by serum skin may be covered with large petechiae analysis during pregnancy, therapy with (“blueberry-muffin” lesions). sulfonamides may be prescribed. However, diagnosis in the mother or infant can ○ Pyrimethamine, an antiprotozoal agent, be established by the isolation of CMV antibodies may also be used. This drug is an anti in blood serum. folic acid drug, so it is administered with Unfortunately, there is no treatment for the caution early in pregnancy to prevent infection even if it presents in the mother with reducing folic acid levels. enough symptoms to allow detection. Because 2. Rubella there is no treatment or vaccine for the disease, The rubella virus usually causes only a mild rash routine screening for CMV during pregnancy is and mild systemic illness in a woman, but the not recommended. teratogenic effects on a fetus can be devastating Women can help prevent exposure by thorough (Johnson & Ross, 2007). hand washing before eating and avoiding crowds Fetal damage from maternal infection with of young children at daycare or nursery settings. rubella (German measles) includes hearing impairment, cognitive and motor challenges, 4. Herpes Simplex Virus (Genital Herpes Infection) cataracts, cardiac defects (most commonly The first time a woman contracts a genital herpes patent ductus arteriosus and pulmonary infection, systemic involvement occurs. The virus stenosis), intrauterine growth restriction (IUGR), spreads into the bloodstream (viremia) and thrombocytopenic purpura, and dental and facial crosses the placenta to a fetus posing substantial clefts, such as cleft lip and palate. fetal risk (ACOG, 2007). Typically, a rubella titer from a pregnant woman If the infection takes place in the first trimester, is obtained on the first prenatal visit. A titer severe congenital anomalies or spontaneous greater than 1:8 suggests immunity to rubella. A miscarriage may occur. titer of less than 1:8 suggests that a woman is If the infection occurs during the second or third susceptible to viral invasion. A titer that is greatly trimester, there is a high incidence of premature increased over a previous reading or is initially birth, intrauterine growth restriction, and extremely high suggests that a recent infection continuing infection of the newborn at birth. has occurred. Unless recognized and treated, the fetal mortality A woman who is not immunized before and morbidity rates are as high as 80% (ACOG, pregnancy cannot be immunized during 2007). pregnancy because the vaccine uses a live virus If a woman has had herpes simplex virus type 1 that would have effects similar to those occurring infections before the genital herpes invasion or if with a subclinical case of rubella. After a rubella the genital herpes (type 2) infection is a immunization, a woman is advised not to become recurrence, antibodies to the virus in her system pregnant for 3 months, until the rubella virus is prevent spread of the virus to a fetus across the no longer active. placenta. All pregnant women should avoid contact with If genital lesions are present at the time of birth, children with rashes. Infants who are born to however, a fetus may contract the virus from mothers who had rubella during pregnancy may direct exposure during birth. For women with a be capable of transmitting the disease for a time history of genital herpes and existing genital after birth. Because of this, an infant may be lesions, cesarean birth is often advised to reduce isolated from other newborns during the newborn the risk of this route of infection. period. This awareness of the placental spread of herpes simplex virus has increased the importance of 3. Cytomegalovirus obtaining information about exposure to genital Cytomegalovirus (CMV), a member of the herpes herpes or any painful perineal or vaginal lesions virus family, is another teratogen that can cause that might indicate this infection at prenatal visits. extensive damage to a fetus while causing few Intravenous or oral acyclovir (Zovirax) can be symptoms in a woman (Lilleri et al.,2007). administered to women during pregnancy (Karch, It is transmitted from person to person by droplet 2009). The primary mechanism for protecting a infection such as occurs with sneezing. fetus, however, focuses on disease prevention. If a woman acquires a primary CMV infection Urging women to practice safe sex is important during pregnancy and the virus crosses the to lessen their exposure to this and other placenta, the infant may be born severely sexually transmitted infections. Advising neurologically challenged (hydrocephalus, adolescents to obtain a vaccine against HPV BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 10  (Gardasil) should lessen the incidence of genital the disease was treated during herpes infection in the future pregnancy. c. The newborn with congenital syphilis 5. Other Viral Diseases may have congenital anomalies, It is difficult to demonstrate other viral extreme rhinitis (sniffles), and a teratogens, but rubeola (measles), characteristic syphilitic rash, all of which coxsackievirus, infectious parotitis (mumps), identify the baby as high risk at birth varicella (chickenpox), poliomyelitis, influenza, (Chakraborty & Luck, 2007). When the and viral hepatitis all may be teratogenic. baby’s primary teeth come in, they are Parvovirus B19, the causative agent of erythema oddly shaped (Hutchinson teeth). infectiosum (also called fifth disease), a common viral disease in school age children, if contracted B. Lyme disease during pregnancy, can cross the placenta and a. Lyme disease, a multisystem disease attack the red blood cells of a fetus. Infection with caused by the spirochete Borrelia the virus during early pregnancy is associated burgdorferi, is spread by the bite of a with fetal death. If the infection occurs late in deer tick. The highest incidence occurs pregnancy, the infant may be born with severe in the summer and early fall. The largest anemia and congenital heart disease (Barankin, outbreaks of the disease are found on 2008). the east coast of the United States (Mullen, 2007). After a tick bite, a typical A. Syphilis skin rash, erythema chronicum migrans a. Syphilis, a sexually transmitted infection, (large, macular lesions with a clear is of great concern for the maternal–fetal center), develops. Pain in large joints population despite the availability of such as the knee may develop. Infection accurate screening tests and proven in pregnancy can result in spontaneous medical treatment, as it is growing in miscarriage or severe congenital incidence and places a fetus at risk for anomalies. intrauterine or congenital syphilis b. To spread the spirochete, the tick must (Walker, 2009). Early in pregnancy, be present on the body possibly as long when the cytotrophoblast layer of the as 24 hours. After returning home from chorionic villi is still intact, the causative an outing, therefore, a woman should spirochete of syphilis, Treponema inspect her body carefully and pallidum, cannot cross the placenta and immediately remove any ticks found. If damage the fetus. When this layer she has any symptoms that suggest atrophies at about the 16th to 18th week Lyme disease or knows she has been of pregnancy, however, the spirochete bitten, she should contact her primary then can cross and cause extensive health care provider immediately. damage. If syphilis is detected and c. Treatment of Lyme disease for pregnant treated with an antibiotic such as women differs from that for nonpregnant benzathine penicillin in the first trimester, women. The drugs used for nonpregnant a fetus is rarely affected. If left untreated adults, tetracycline and doxycycline, beyond the 18th week of gestation, cannot be used during pregnancy hearing impairment, cognitive challenge, because they cause tooth discoloration osteochondritis, and fetal death are and, possibly, long-bone malformation in possible. a fetus. A course of penicillin will be b. For this reason, serologic screening (by prescribed to reduce symptoms in the either a VDRL or a rapid plasma reagin pregnant woman. test) should be done at a first prenatal d. Because the symptoms of Lyme disease visit; the test may then be repeated are chronic but not dramatic (a migratory again close to term (the 8th month) if rash and joint pain), women may not exposure is a concern. Even when a report them at a prenatal visit unless woman has been treated with they are educated about their appropriate antibiotics, the serum titer importance and are asked at prenatal remains high for more than 200 days; an visits if such symptoms are present. increasing titer, however, suggests that reinfection has occurred. In an infant 6. Potentially Teratogenic Vaccines born to a woman with syphilis, the Live virus vaccines, such as measles, HPV, serologic test for syphilis may remain mumps, rubella, and poliomyelitis (Sabin type), positive for up to 3 months even though are contraindicated during pregnancy because BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 11  they may transmit the viral infection to a fetus incidence of congenital deformities and cognitive (Rojas, Wood, & Blakemore, 2007). Care must impairment. It was assumed in the past that be taken in routine immunization programs to these defects were the result of the mother’s make sure that adolescents about to be poor nutritional status (drinking alcohol rather vaccinated are not pregnant. Women who work than eating food), not necessarily the direct result in biologic laboratories where vaccines are of the alcohol. manufactured are well advised not to work with However, alcohol has now been firmly isolated as live virus products during pregnancy. a direct teratogen. Fetuses cannot remove the breakdown products of alcohol from their body. 7. Teratogenic Drugs The large buildup of this leads to vitamin B Many women, assuming that the rule of being deficiency and accompanying neurologic cautious with drugs during pregnancy applies damage. only to prescription drugs, take over-the-counter Women during pregnancy should be screened for drugs or herbal supplements freely. Although not alcohol use because an infant born with fetal all drugs cross the placenta (heparin, for alcohol syndrome (FAS) not only is small for example, does not because of its large molecular gestational age but can be cognitively challenged size), most do. Also, even though most herbs are (Shankar, Ronis, & Badger, 2007). safe, ginseng, for example, used to improve Women are best advised, therefore, to abstain general well-being, or senna, used to relieve from alcohol completely. Be certain to ask about constipation, may not be safe (Der Marderosian binge drinking (consuming more than five & Beutler, 2007). alcoholic drinks in an evening) as women may Any drug or herbal supplement, under certain refer to this as only “occasional drinking.” Refer circumstances, may be detrimental to fetal women with alcohol addiction to an alcohol welfare. Therefore, during pregnancy, women treatment program as early in pregnancy as should not take any drug or supplement not possible to help them reduce their alcohol intake. specifically prescribed or approved by their physician or nurse-midwife. 9. Teratogenicity of Cigarettes A woman of childbearing age and ability should Cigarette smoking is associated with infertility in not take any drug other than one prescribed by a women. Cigarette smoking by a pregnant woman physician or nurse-midwife to avoid exposure to has been shown to cause fetal growth restriction a drug should she become pregnant. (Lawrence & Haslam, 2007). In addition, a fetus The use of recreational drugs during pregnancy may be at greater risk for being stillborn puts a fetus at risk in two ways: the drug may (Hogberg & Cnattingius, 2007) and, after birth, have a direct teratogenic effect, and intravenous may be at greater risk than others for sudden drug use risks exposure to diseases such as HIV infant death syndrome. Low birth weight in and hepatitis B (Donnelly et al., 2008). infants of smoking mothers results from Narcotics such as meperidine (Demerol) and vasoconstriction of the uterine vessels, an effect heroin have long been implicated as causing of nicotine. This limits the blood supply to a fetus. intrauterine growth restriction (IUGR). The use of Another contributory effect may be related to marijuana alone apparently does not, although inhaled carbon monoxide. Secondary smoke, or the long-term effects of marijuana during inhaling the smoke of another person’s pregnancy are still unstudied. Cocaine, cigarettes, may be as harmful as actually particularly its crack form, is potentially harmful to smoking the cigarettes. All prenatal healthcare a fetus because it causes severe settings should be smoke-free environments for vasoconstriction in the mother, compromising this reason. placental blood flow and perhaps dislodging the The best way to urge women to discontinue placenta. Its use is associated with spontaneous smoking is to educate them about the risks to miscarriage, preterm labor, meconium staining, themselves and their fetus at a first prenatal visit. and IUGR (Rojas, Wood, & Blakemore, 2007). It may be effective to encourage women to sign a An area of recreational drug use that needs to be contract with a health care provider to try to stop examined is that of inhalant abuse (“huffing”). or to join a smoking-cessation program. Substances frequently used as inhalants include gasoline, butane lighter fluid, Freon, glue, and 10. Radiation nitrous oxide (NIOSH, 2007). Rapidly growing cells are extremely vulnerable to destruction by radiation. That makes radiation a 8. Teratogenicity of Alcohol potent teratogen to unborn children because of Evidence over the years has shown that when their high proportion of rapidly growing cells. women consume a large quantity of alcohol Radiation produces a range of malformations during pregnancy, their babies show a high depending on the stage of development of the BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 12  embryo or fetus and the strength and length of exposure. If the exposure occurs before implantation, the growing zygote apparently is killed. If the zygote is not killed, it survives apparently unharmed. The most damaging time for exposure and subsequent damage is from implantation to 6 weeks after conception (when many women are not yet aware that they are pregnant). The nervous system, brain, and retinal innervation are most affected. As a rule, therefore, all women of childbearing age should be scheduled for pelvic x-ray examinations only in the first 10 days of a menstrual cycle (when pregnancy is unlikely because ovulation has not yet occurred), except in emergency situations. A serum pregnancy test can be done on all women who have reason to believe they might be pregnant before diagnostic tests involving x-rays are scheduled. BATCH 2025 TRANSCRIBED BY: AJ & MJ | PLEASE DO NOT REMOVE THIS TO GIVE CREDIT FOR THEIR EFFORTS. 13