Fetal Development Stages PDF

THE GROWING FETUS  STAGES OF FETAL DEVELOPMENT Terms use to denote fetal growth Name Time period Ovum From ovulation to fertilization Zygote From fertilization to implantation Embryo From implantation to 5-8 wks Fetus From 5-8 wks until term Con...

THE GROWING FETUS  STAGES OF FETAL DEVELOPMENT Terms use to denote fetal growth Name Time period Ovum From ovulation to fertilization Zygote From fertilization to implantation Embryo From implantation to 5-8 wks Fetus From 5-8 wks until term Conceptus Developing embryo or fetus and placental structures throughout pregnancy Ovum Zygote Embryo Fetus – 9 weeks Newborn FERTILIZATION: The Beginning of Pregnancy I. Fertilization : The Beginning of Pregnancy Fertilization (conception ,impregnation,or fecundation ) -the union of an ovum and a spermatozoon in the outer third of a fallopian tube, the ampullar portion. General consideration:  only one ovum reaches maturity each month.  once released, fertilization must occur fairly quickly  ovum is only capable of fertilization for only 24 hours (48 hours at the most)  after that, it atrophies and becomes nonfunctional. The total critical time span then, for fertilization to be successful is about 72 hours ( 48 hrs before ovulation plus 24 hrs afterward). Ovum Zona Pellucida – ring of mucupolysaccharide fluid surrounding an ovum. Corona radiata - circle of cells Zona Pellucida and Corona radiata - increase the bulk of the ovum and serve as protective buffers against injury.  Ovum is propelled into a nearyby fallopian tube by currents initiated by the fimbriae-the fine hairlike structures that line the openings of the fallopian tube. A combination of peristaltic action of the tube and movements of the tube cilia help propel the ovum along the length of the tube.  Sperm normal amount of semen per ejaculation – 2.5 ml of fluid Number of sperms/cc/ml – 50-200 million or average of 400 million sperm per ejaculation. Sperms are capable of fertilizing even for 3-4 days after ejaculation.  Normal life span of sperms – 7 days  Sperms, once deposited in the vagina, will generally reach the cervix within 90 seconds. reaches outer fallopian tube within 5 minutes ( this is why douching is not an effective contraceptive)  Spermatozoa move by means of their flagella (tails) and uterine contractions through the cervix and the body of the uterus and into the fallopian tubes, toward the waiting ovum.  Capacitation – the final process that sperm must undergo to be ready for fertilization. - consists of changes in the plasma membrane of the sperm head , which reveal the sperm- binding receptor site. - all of the spermatozoa that achieve capacitation reach the ovum and cluster around the protective  Hyaluronidase( a proteolytic enzyme) – released by the spermatozoa and acts to dissolve the layer of cells protecting the ovum.  Zygote- the resulting structure when chromosomal material of the of the ovum and spermatozoon fuse immediately after the penetration of the ovum. * ZYGOTE Zygote – 46 chromosomes chromosomes – DNA-containing structure of cellular organism autosomes – chromosomes that do not determine the sex * Sperm ( 22 autosomes and 1 X or 1 Y sex chromosomes ) * Ova ( 22 autosomes and 1 X sex chromosome)  Only fathers determine the sex of their children. Ex. The union of Y-carrying sperm and a mature ovum results in a baby boy (XY). If xx – results in a baby girl  Fertilization is never a certain occurrence because it depends on at least three separate factors: 1. equal maturation of both sperm and ovum, 2. the ability of the sperm to reach the ovum, 3. The ability of the sperm to penetrate the zona pellucida and cell membrane and achieve fertilization. Implantation Fertilization is complete – over 3-4 days – zygote migrates toward the body of uterus --- mitotic cell division or cleavage begins (blastomere) --- 1st cleavage occurs at about 24 hrs --- cleavage divisions continue to occur at a rate of one about every 22 hrs --- consists of 16 to 50 cells by the time the zygote reaches the body of the uterus --- now known as morula. Morula continues to multiply as it floats freely in the uterine cavity for 3 or 4 more days --- large cells tend to collect at the the periphery of the ball, leaving a fluid space sorrounding the inner cell mass---now known as blastocyst ( the structure that attaches to the uterine endometrium). The cells in the outer ring are trophoblast cells. They are part of the structure that will later form the placenta and membranes. The inner cell mass ( embryoblast cells) is the portion of the structure that will form the embryo.  Trophoblast – are cells in the outer ring. Part of the structure that will later form the placenta and membranes. They produce proteolytic enzymes that dissolve any tissue they touch. The action allows the blastocyst to burrow deeply into the endometrium and receive basic nourishment of glycogen and mucoprotein from the endometrial gland.  THE INNER CELL MASS - while trophoblast is developing into the placenta, which will nourish the fetus, the inner cell mass is forming the fetus itself. Three layers of the inner cell mass: 1. The ectoderm – forms the skin and nervous system. 2. The mesoderm – forms bones and muscles and also the heart and blood vessels, including those in the placenta. 3. The endoderm – forms mucous membranes and glands. * the three layers together are known as the embryonic plate. Implantation, or contact between the growing structure and the uterine endometrium, occurs approximately 8 to 10 days after fertilization. After 3rd or 4th day of free floating ( about 8 days since ovulation) –the blastocyst sheds the last residues of the corona and zona pellucida. The structure brushes against the rich uterine endometrium, a process termed apposition. It attaches to the surface of the endometrium (adhesion) and settles down into its soft folds ( invasion ).  …and settles down into its soft folds ( Invasion ). 6 day-old human embryo implanting  Implantation point is usually high in the uterus, on the posterior surface. Abnormal Implantation This drawing illustrates a phenomenon known as implantation bleeding. Maternal blood fills the cavities in the trophoblast. The trophoblast surrounds the whole embryo and just before it is completely covered some of blood in the superficial cavities might leak into the uterine cavity and escape via the vagina. This implantation bleeding occurs exactly at the time of the expected Once implanted, the zygote becomes an embryo EMBRYONIC AND FETAL STRUCTURES  The placenta, which will serve as the fetal lungs, kidneys, and digestive tract in utero, begins growth in early pregnancy in coordination with embryo growth. The decidua - after fertilization, the corpus luteum continues to function because of the influence of hCG. Uterine endometrium continues to grow in thickness and vascularity. Endometrium is now termed decidua and will be discarded only after birth. A. The Decidua ( latin: falling off ) - the name given to the endometrium during pregnancy. Three separate areas: 1. Decidua Basalis – lies directly under the embryo. 2. Decidua capsularis – the portion of the endometrium that stretches or encapsulates the surface the surface of the trophoblast. 3. Decidua vera – the remaining portion of the The Decidua - as embryo continues to grow, it pushes the decidua capsularis before it like a blanket. - Eventually, enlargement brings the structure into contact with the opposite uterine wall. - At birth, the entire inner surface of the uterus is stripped away, leaving the organ highly susceptible to hemorrhage and infection. B. Chorionic Villi - initially the ovum appears to be covered with fine, downy hair surrounding the ovum. - these proliferate and branch from about 3 weeks after fertilisation , forming the chorionic villi. - - at term, almost 200 villi will have formed. - - it is most profuse in the area where the blood supply is the richest – that is, the basal decidua. - - the villi erode the walls of maternal blood vessels as they penetrate the decidua, opening them up to form a lake of maternal blood in which they float. A few villi are more deeply attached to the decidua and are called TWO OUTER COVERING : 1. The syncytiotrophoblast- capable of breaking down tissue as in the process of embedding. It erodes the walls of the blood vessels of the decidua, making nutrients in the maternal blood accesible to the developing organism. - produces hCG, somatomammotropin, estrogen and progesterone TWO OUTER COVERING : 2. The cytotrophoblast – The hormone is responsible for informing the corpus luteum that a pregnancy has begun. The corpus luteum continues to produce estrogen and progesterone. Menstruation then is supressed. - protect the growing embryo and fetus from certain infectious organisms such as spirochete of syphilis.  Cytotrophoblast or Langhans layer –is present as early as 12 days gestation. - disappears between the 20th and 24th week. - the reason why syphillis is considered to have a high potential for fetal damage late in pregnancy. C. THE PLACENTA ( latin for pancake )  arises out of trophoblast tissue  it serves as the fetal lungs, kidneys, and gastrointestinal tract and as a separate endocrine organ throughout pregnancy.  its growth parallels that of the fetus, growing from a few identifiable cells at the beginning of pregnancy to an organ 15  Placental Circulation 12th day of pregnancy – maternal blood begins to collect in the intervillous spaces of the uterine endometrium sorrounding the chorionic villi. 3rd week : oxygen and other nutrients, such as glucose, amino acids, fatty acids, minerals, vitamins, and water diffuse from the maternal blood through the cell layers of the chorionic villi to the villi capillaries. From there: nutrients are transported back to the developing embryo. Note: There is no direct exchange of blood between the embryo and the mother during the pregnancy. The exchange is carried out only by selective osmosis through the chorionic villi. Minute break allow occasional fetal cells to cross as chorionic villi is only one cell thick. Placental osmosis is so effective that all but a few substances are able to cross from the mother into the fetus. It is important that a woman take no nonessential drugs ( including alcohol and nicotine) during pregnancy.  Mechanisms by Which Nutrients Cross the Placenta Mechanism Description Diffusion When there is a greater concentration of a substance on one side of a semipermeable membrane than on the other, substances of correct molecular weight cross the membrane from the area of higher concentration to the area of lower concentration. Oxygen, carbon dioxide, sodium, and chloride cross the placenta by this method. Facilitated diffusion To ensure that the fetus receives enough concentrations of necessary growth substances, some substances cross the placenta more rapidly or more easily without the expenditure of energy. A carrier moves the substance into and through the membrane. Glucose is an example of a substance that crosses by this process. Active transport This process requires energy and action of an enzyme to facilitate transport. Essential amino acids and water-soluble vitamins cross the placenta against the pressure gradient or from an area of lower molecular concentration to an area of greater molecular concentration. Pinocytosis Absorption by the cellular membrane of microdroplets of plasma and dissolved substances. Gamma globulin, lipoproteins, phospholipids, and other molecular structures that are too large for diffusion and that cannot participate in active transport cross in this manner. Viruses that infect the fetus can also cross in this manner. Cotyledons - as the number of chorionic villi increases with pregnancy, the villi form an increasingly complex communication network with the maternal blood. - intervillous spaces grow larger and larger, becoming separated by a series of partitions or septa. - in a mature placenta, there as many as 30 separate segments, called cotyledons. - these compartments are what make the maternal side of the placenta at term look rough and uneven. Cotyledons Duncan/Shultz presentation Blood supply - 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 50ml/min at 10 weeks to 500 to 600 ml/min at term. - no additional maternal arteries appear after the first 3 months of pregnancy; instead, to accommodate the increased blood flow, the arteries increase in size. _ Systematically, the mother’s heart rate, total cardiac output, and blood volume increase to supply the placenta.  Uterine perfusion and placental circulation is most efficient when the mother lies on her left side. This position lifts the uterus away from the inferior vena cava, preventing blood from being trapped in her lower extremities. If the mother lies on her back and the weight of the uterus compresses the vena cava, placental circulation can be so sharply reduced that supine hypotension occurs.  At term, placental circulatory network has grown so extensively that a placenta weighs 400 to 600 g( 1 lb ). Smaller placenta : suggests that circulation to the fetus may have been inadequate. Bigger placenta : may indicate that circulation to the fetus was threatened, because the placenta was forced to spread out in an unusual manner to maintain a sufficient blood supply. E.g., mother with diabetes ( probably from excess fluid collected between the cells)  Endocrine Function in pregnancy 1. Human Chorionic Gonadotropin - first hormone produced - can be found in maternal blood and urine as early as the first missed menstrual period ( shortly after implantation has occurred) - a false-negative result from a pregnancy test may be reported before or after this period. - mother’s serum will be completely negative for hCG within 1 to 2 weeks after birth. - testing for hCG after birth can be used as proof that all of the placental tissue has been delivered. Role of hCG a. act as a fail-safe measure to ensure that the corpus luteum of the ovary continues to produce progesterone and estrogen. - if corpus luteum should fail and the level of progesterone fall, this would cause endometrial sloughing, with loss of pregnancy followed by a rise of pituitary gonadotropins to induce menstrual cycle. b. Supressess the maternal immunologic response so that placental tissue is not rejected c. If fetus is male, it exerts an effect on the fetal testes to begin testosterone production, because hCG structure is similar to that of LH. 2. Estrogen - produced as a second product of the syncytial cells of the placenta. - contributes to the mother’s mammary gland in preparation for lactation and stimulates uterine growth to accommodate the developing fetus. - “ hormone of women” 3. Progesterone - “ hormone of mothers” - necessary in pregnancy to maintain the endometrial lining of the uterus. - present in serum as early as the 4th week of pregnancy. - rises progressively during the remainder of pregnancy - helps prevent premature labor as it reduces the contractility of the uterine musculature during 4. Human Placental lactogen ( Human Chorionic Somatomammotropin) - a hormone with both growth-promoting and lactogenic (milk-producing) properties. - produced by the placenta as early as the 6th week of pregnancy. - be assayed in both maternal serum and urine. - promotes mammary gland growth in preparation for lactation in the mother. - also serves the important role of regulating maternal glucose, protein, and fat levels so that adequate amount of these nutrients are always available to the fetus.  THE AMNIOTIC MEMBRANES Formation of Chorion - the chorionic villi on the medial surface of the trophoblast gradually thin, leaving the medial surface of the structure smooth (smooth chorion ) - smooth chorion eventually becomes the chorionic membrane, the outermost fetal membrane. - once it becomes smooth, it offers support to the sac that contains the amniotic fluid. Formation of Amnion - second membrane lining the chorionic membrane - forms beneath the chorion - at birth, they can be seen covering the fetal surface of the placenta, giving that surface its typically shiny appearance. - no nerve supply - spontaneously rupture at term or artificially ruptured - produces the amniotic fluid - also produces a phospholipid that initiates the formation of prostaglandins, which can cause uterine contractions and may be the trigger that initiates labor. Amnion/Chorion The Amniotic Fluid - is constantly being newly formed by the amniotic membrane, so it never becomes stagnant. - slightly alkaline, with a pH of about 7.2 - absorption : a. direct contact with the fetal surface of the placenta b. fetus continually swallows the fluid, the major method of absorption c. in the fetal intestine, it is absorbed into the fetal bloodstream – umbilical arteries – to placenta – exchanged across the placenta. Amount at term – 800-1,200 mL Hydramnios – excessive amniotic fluid - more than 2,000 mL - commonly due to : esophageal atresia or anencephaly - also tends to occur in women with diabetes Oligohydramnios – reduction in the amount of amniotic fluid - due to the disturbance in the fetal kidney function - less than 300 mL Function of amniotic fluid: -serves as important protective mechanism for fetus. - shield against pressure or a blow to the mother’s abdomen. - protects fetus from changes of temperature - probably aids in muscular development, because it allows the fetus the freedom to move. - protects the umbilical cord from pressure, protecting the fetal oxygen supply. D. The umbilical Cord UMBILICAL CORD/FUNIS i. Description - is formed from the fetal membranes ( amnion and chorion ) - provides a circulatory pathway that connects the embryo to the chorionic villi of the placenta. ii. Function - transport oxygen and nutrients to the fetus from the placenta and to iii. Characteristics - about 53 cm (21 in) in length at term - about 2 cm ( ¾ in ) thick - bulk of the cord is gelatinous mucopolysaccharide called “ Wharton’s jelly “, it gives the cord body and prevents pressure on the vein and arteries that pass through it. - outer surface is covered with amniotic membrane.  - umbilical cord contains : 1 vein ( carrying blood from the placental villi to the fetus), and 2 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. - blood can be withdrawn from the umbilical vein or transfused into the vein during intrauterine life for fetal assessment or treatment. - rate of blood flow: 350 mL/min at term and rapid - cord is unlikely to twist or knot due to its rapidity  - in about 20% of all births, a loose loop of cord is found around the fetal neck ( nuchal cord). - wall of umbilical cord arteries are lined with smooth muscle. Constriction of these muscles after birth contributes to hemostasis and helps prevent hemorrhage. - it does not contain nerve supply, thus it can be cut at birth without discomfort to either the child or mother. Umbilical cord Dry umbilical cord  ORIGIN AND DEVELOPMENT OF ORGAN SYSTEMS A. Stem Cells B. Zygote Growth C. Primary Germ Layers D. Cardiovascular System E. Fetal Circulation F. Fetal Hemoglobin G. Respiratory System H. Nervous System I. Endocrine System J. Digestive System K. Musculoskeletal System L. Reproductive System M. Urinary System N. Integumentary system O. Immune system  A. Stem Cells 1. Totipotent stem cells ( zygote cells ) - occurs during the first 4 days of life - so undifferentiated that they have the potential to form a complete human being. 2. Pluripotent stem cells - in another 4 days, the structure implants and becomes an embryo- begin to show diferentiation and are no longer capable of becoming any body cell – slated now to become specific body cells, such as nerve, brain, or skin cells. 3. Multipotent stem cells - specific that they have set a sure course toward what body organ they will create. 2 types of Cloning: 1. Reproductive cloning - the nucleus is removed from an oocyte and the nucleus of an adult cell is transferred into the oocyte, the embryo has the potential to grow into an infant that is identical to the adult donor. 2. Therapeutic cloning - pluripotent stem cells are removed and allowed to grow in the laboratory, these have the potential to be able to supply any type of body cell needed by the adult donor.  B. Zygote Growth Development proceeds in a cephalocaudal direction.  C. Primary Germ layer 1. Ectoderm : a distinctive layer of cells, arises from amniotic cavity which is the largest. 2. Entoderm : arises from the yolk sac , a smaller cavity - yolk sac appears to supply nourishment only after implantation. - after that, its main purpose is to provide a source of red blood cells until the embryo’s hematopoetic system is mature enough to perform this function. - it then atrophies and remains only as white streak discernible in the cord at birth. 3. Mesoderm – 3rd layer Implications of the Primary Germ layers: - each of these germ layers, primary tissue develops into specific body systems ( see table) - coexisting congenital defects found in newborns usually arise from the same layer. ex. Esophageal and tracheal fistula ( entoderm ) Heart and kidney defects ( mesoderm) Bladder and urethral defects ( entoderm ) Note: - Rubella infection is serious in pregnancy as it can infect all three germ layers, thereby causing congenital anomalies - Screening procedures are ordered for newborns with congenital malformations. e.g radiographic exam of the kidney with a child born with heart defects. Germ Layer Body Portions Formed Ectoderm Central nervous system (brain and spinal cord) Peripheral nervous system Skin, hair, and nails Sebaceous glands Sense organs Mucous membranes of the anus, mouth, and nose Tooth enamel Mammary glands Mesoderm Supporting structures of the body ( connective tissue, bones, cartilage, muscle, ligaments and tendons ) Dentin of teeth Upper portion of the urinary system ( kidneys and ureters ) Reproductive system Heart Circulatory system Blood cells Lymph vessels Entoderm Lining of pericardial, pleura, and peritoneal cavities Lining of the gastrointestinal tract, respiratory tract, tonsils, parathyroid, thyroid, thymus glands Lower urinary system ( bladder and urethra )  At 8 week’s gestation ( the end of embryonic period), all organ system are complete. Organogenesis – the growing structure is most vulnerable to invasion by teratogens ( see fig 8.5 Critical periods of fetal growth.p 191, Pillitteri) D. Cardiovascular System One of the first system to become functional in intrauterine life. Forms as early as the 16th day of life and beats as early as the 24th day. 6th or 7th week: septum that divides the heart into chambers is developed. 10th to 12th week : heartbeat maybe heard thru a Doppler instrument 11th week : ECG After 28th wk : 5 beats/min thru a fetal heart rate rhythm strip.  d1. Fetal Circulation  3rd week of intrauterine life, fetal blood begins to exchange nutrients with maternal circulation across the chorionic villi.  Fetus derives oxygen and excretes carbon dioxide from the placenta.  The blood flow is to supply the cells of the lungs.  Specialized structures present in the fetus shunt blood flow to supply the most important organs of the body: the brain, the heart, and kidneys.  Blood from the placenta is highly oxygenated.  Blood enters the fetus through the umbilical vein (called a vein even though it carries Fetal circulation  This vein carries the blood to the inferior vena cava through an accessory structure, the ductus venosus, which allows oxygenated blood to be supplied directly to the fetal liver.  Oxygenated blood then empties into the inferior vena cava and is carried to the right side of the heart.  The blood then enters the right atrium, into the left atrium through an opening in the atrial septum, called foramen ovale.  From the left atrium, it follows the course of normal circulation into the left ventricle and into the aorta.  Ductus arteriosus- shunts away from the lungs small amount of blood that returns to the heart directly into the descending aorta.  Most of the blood flow from the descending aorta is transported by the umbilical arteries ( called arteries, even though they are now transporting deoxygenated blood, bec they are carrying blood away from the fetal heart) back through the umbilical cord to the placental villi, where new oxygen exchange takes place.  80% - blood oxygen saturation level of the fetus Rapid fetal heart rate ( 120 to 160/min ) is necessary to supply oxygen to cells. d2. Fetal hemoglobin Compose of two alpha and two gamma chains ( adult: two alpha and two beta chains) More concentrated Has greater oxygen affinity 17.1g/100mL hg level (adult : 11g/100 mL) 53% hct level ( adult : 45% )  E. Respiratory System 3rd week: respiratory and digestive tracts exist as single tube. Initially it is a solid structure, canalizes then by end of 4th week, a septum begins to divide the esophagus and trachea- at the same time, lung buds appear on the trachea. Note: Diaphragmatic hernia or intestine still present in the chest occurs if the diaphragm fails to close completely by end of 7th week. Important respiratory developmental milestones : Alveoli and capillaries begin to form between the 24th and 28th weeks. 3 mos : spontaneous respiratory practice movts begin Specific lung fluid with a low surface tension and low viscosity forms in alveoli to aid in expansion of the alveoli at birth; it is rapidly absorbed after birth. Surfactant , formed at about the 24th week.  F. Nervous Begins to developSystem extremely early in pregnancy, during the 3 rd and 4th weeks of life. Milestones : 3rd week : neural plate ( thickened portion of the ectoderm) is apparent. - top portion differentiates into the neural tube, which form into brain and spinal cord. 8th week : brain waves can be detected by EEG All parts of the brain form in utero. The eye and inner ear develop as projections of the original neural tube. 24 weeks : ear is capable of responding to sound; eyes exhibit a pupillary reaction, indicating that sight is present. Note: - Meningocele ( spinal cord disorder ) – may occur because of lack of folic acid.  G. Endocrine System Fetal adrenal glands supply a precursor for estrogen synthesis by the placenta. The fetal pancreas produces the insulin needed by the fetus ( insulin does not cross the placenta from the mother to the fetus ) The thyroid and parathyroid glands play vital roles in metabolic function and calcium balance. H. Digestive System 4th week ; separates from the respiratory tract 16th week : meconium forms GIT tract is sterile before birth, vitamin K level is low 32 weeks or 1,500 g : sucking and swallowing reflexes matures 36 weeks: ability of the GIT to secrete enzymes essential to carbohydrate and protein digestion is mature. Liver is active throughout gestation - functions as filter between the incoming blood and fetal circulation - and a deposit site for fetal store such as iron and glycogen  I. Musculoskeletal System 11th week : fetus can be seen moving through ultrasound 20 weeks : quickening can be felt by the mother  J. Reproductive Child’s sex isSystem determined at the moment of conception 8th week : can be ascertained through chromosomal analysis 6th week: gonads ( testes and ovaries ) form Testes first form in the abdominal cavity 34th to 38th week : testes descend into the scrotal sac Note: * If testes is formed : testosterone is secreted influencing the sexually neutral genital duct to form other male organs ( maturity of the wolffian, or mesonephric, duct ).  * if no testosterone : female organs will form ( maturation of the müllerian, or paramesonephric, duct). Importance : * if mother should take an androgen-like substance during this stage of pregnancy, a child who is chromosomally female would appear more male than female at birth. * if deficient testosterone is secreted by the testes, both the müllerian duct and the wollfian duct could develop (pseudo-hermaphroditism, or intersex ).  K. Urinary System End of 4th week : kidneys are present but is not essential as the placenta clears the fetus of waste products. 12th week : urine is formed 16th week: urine is excreted into the amniotic fluid At term : fetal urine is being excreted at the rate of 500 mL/day. Oligohydramnios ( amount of amniotic fluid that is less than normal ) suggests that fetal kidneys are not secreting adequate urine.  L. Integumentar yaSystem The skin of fetus appears thin and almost translucent until subcutaneous fat begins to be deposited at about 36 weeks. Skin is covered by : lanugo - soft downy hairs) vernix caseosa - a cream cheese-like substance, important for lubrication and for keeping the skin from macerating in utero.  M. Immune System Third trimester : IgG maternal antibodies cross the placenta into the fetus - give the fetus temporary passive immunity against diseases for which the mother has antibodies. - includes poliomyelitis, rubella, rubeola, diptheria, tetanus, infectious parotitis, hep B, and pertussis. - fetus is susceptible to herpes virus as there is little or no immunity at all - level of immunity peaks at birth and then decreases over the next 8months while the infant begins to build up his or her own stores of IgG, IgA and IgM. 2 months : immunization is started as passive immunity declines MILESTONES of FETAL GROWTH and DEVELOPMENT MILESTONES of FETAL GROWTH and DEVELOPMENT Day 1: fertilization: all human chromosomes are present; unique human life begins.  Day 6: embryo begins implantation in the uterus. Day 22: heart begins to beat with the child's own blood, often a different type than the mothers'. Week 3: By the end of third week the child's backbone spinal column and nervous system are forming. The liver, kidneys and intestines begin to take shape. Week 4: Length: 0.75 to 1 cm Weight : 400 mg Week 5: Eyes, legs, and hands begin to develop. Week 6: Brain waves are detectable; mouth and lips are present; fingernails are forming. Week 7: Eyelids, and toes form, nose distinct. The baby is kicking and swimming. Week 8: Every organ is in place, bones begin to replace cartilage, and fingerprints begin to form. By the 8th week the baby can begin to hear. Length : 2.5 cm ( 1 in ) Weight : 20 g Organogenesis is complete. The heart, with septum and valves, is beating rythmically. Facial features are definitely discernible. Arms and legs are developed. External genitalia are present, but sex is not distinguishable by simple observation. The primitive tail is regressing. Abdomen appears large because the fetal intestine is growing rapidly. Sonogram shows a gestational sac, diagnostic of pregnancy.  Weeks 9 and 10: Teeth begin to form, fingernails develop. The baby can turn his head, and frown. The baby can hiccup. Weeks 10 and 11: The baby can "breathe" amniotic fluid and urinate. Week 11: the baby can grasp objects placed in its hand; all organ systems are functioning. The baby has a skeletal structure, nerves, and circulation. Week 12( First trimester ): The baby has all of the parts necessary to experience pain, including nerves, spinal cord, and thalamus. Vocal cords are complete. The baby can suck its thumb. Length : 7 to 8 cm Weight :45 g Sex is distinguishable by outward appearance Kidney secretion has begin Heartbeat is audible through Doppler Week 14: At this age, the heart pumps several quarts of blood through the body every day.  Week 15: The baby has an adult's taste buds. Month 4: Bone Marrow is now beginning to form. The heart is pumping 25 quarts of blood a day. By the end of month 4 the baby will be 8-10 inches in length and will weigh up to half a pound. Week 17: The baby can have dream (REM) sleep. Week 19: Babies can routinely be saved at 21 to 22 weeks after fertilization, and sometimes they can be saved even younger. Week 20: The earliest stage at which Partial birth abortions are performed. At 20 weeks the baby recognizes its' mothers voice. Length : 25 cm Weight : 223 g Spontaneous fetal movements can be felt by the mother Antibody production is possible. Hair forms extending to include eyebrows and hair in the head. Meconium is present in the upper intestine. Brown fat starts to develop Vernix caseosa begins to form. End of 24th Gestational week ( Second Trimester ) The baby practices breathing by inhaling amniotic fluid into its developing lungs. The baby will grasp at the umbilical cord when it feels it. Most mothers feel an increase in movement, kicking, and hiccups from the baby. Oil and sweat glands are now functioning.  Length: 28 to 36 cm Weight: 550g Pupils are capable of reacting to light. Achieved a practical low-end age of viability if they are cared in a modern intensive care facility and has a weight of 601 g. Hearing can be demonstrated by response to sudden sound.  Months 7 through 9: Eyeteeth are present. The baby opens and closes his eyes. baby is using four of the five senses (vision, hearing, taste, and touch.) He knows the difference between waking and sleeping, and can relate to the moods of the mother. The baby's skin begins to thicken, and a layer of fat is produced and stored beneath the skin. Antibodies are built up, and the baby's heart begins to pump 300 gallons of blood per day. Approximately one week before the birth the baby stops growing, and "drops" usually head down into the pelvic cavity.  End of 40th Gestational week Length: 48 to 52 cm Weight: 1,800 to 2,700g ( 5 to 6 lb) Fetus kick actively Fetal hemoglobin begins its conversion to adult hemoglobin Vernix caseosa is fully formed. Creases of the soles of the feet cover at least two thirds of the surface. MEASUREMENT of the LIFE of FETUS MEASUREMENT of the LIFE of FETUS Ovulation age Gestational age – measured from the first day of the last menstrual cycle Lunar mos – 4 weeks period Trimesters – 3 mos period Lunar mos – 10 mos ( 40 wks or 280 days ) Determination of Estimated Birth Date Traditionally, this date has been referred to as the estimated date of confinement ( EDC). Changed to EDB as women are no longer “confined’ after childbirth. If fertilization occurred early in a menstrual cycle, the pregnancy will probably end “early” If ovulation and fertilization occurred later in the cycle, the pregnancy will end “late”. Because of these, a pregnancy ending 2 weeks before or 2 weeks after the calculated EDB is considered. Nagele’s Rule : standard method to predict the length of pregnancy. 1. Determine the last normal menstrual period (LMP). 2. Consider the FIRST DAY of the LMP. 3. Consider the month in numerical term. for example : Jan = 1 April = 4 Feb = 2 May = 5 and so forth. For the first 3 months of the year, add 12 to the numerical value. for example : January : 1 + 12 = 13 February : 2 + 12 = 14 March : 3 + 12 = 15  4. Now use the Nagele’s Formula : subtract 3 months and add 7 days to the first day of LMP. example A : Given LMP is January 5 – 10. Numerical value of January is 13: 13 5 - 3 10 5 + 7 - 10 12 EDD is October 12. Example B : Given LMP is September 12 – 17. Numerical value of September is 9. 9 12 -3 6 12 + 7 6 19 Note: The Nagele’s Rule is just an estimate. It is said that 4% of all babies arrive “on time” using this rule, whereas 60% appear 1 to 7 days early or late. Estimating Age of Gestation LMP : Jan. 2, 2016 Clinic Visit : July 29, 2016 Computation: Jan 31 – Jan 2 = 29 Feb = 28 March = 31 April = 30 May = 31 June = 30 July = 29 _______ 208 / 7 = 29.7 or : 29 x 7 = 203 – 208 = 5 29 weeks and 5 days in months : 29/ 4 weeks = 7.2 months or 7 x 4 = 28 – 29 = 1 week therefore AOG is : 7 months , 1 week and 5 days ASSESSMENT OF GROWTH AND DEVELOPMENT ASSESSMENT OF FETAL GROWTH AND DEVELOPMENT IMPORTANCE: * Fetal growth and development can be compromised if : - a fetus has a metabolic or chromosomal disorder that interferes with normal growth, - if the supporting structures such as the placenta or cord do not form normally - or if environmental influences, such as cigarette smoking or alcohol consumption interfere with fetal growth. Nursing responsibilities: 1. Seeing that a signed consent form has been obtained as needed. 2. Scheduling the procedure 3. Explaining the procedure to the woman and her support person 4. Preparing the woman physically and psychologically 5. Providing support during the procedure 6. Assessing both fetal and maternal responses to the procedure 7. Providing any necessary follow-up care 8. Managing equipment and specimens A. Health History 1. nutritional intake 2. personal habit 3. any accidents or experienced intimate partner abuse B. Estimating Fetal Growth a. Estimating Fundic Height by McDonald’s Method ( indicator of uterine size in early pregnancy)  EQUIPMENT : A centimeter tape measure PROCEDURE : 1. Explain the procedure to the mother. 2. Ask the mother to empty her bladder. A full bladder displaces the uterus causing an inaccurate measurement. 3. Position mother on dorsal recumbent. 4. Drape. 5. Measure the distance abdominally from the top of the symphysis pubis over the curve of the abdomen to the top of the uterine fundus. Fundic height ( FH ) in cm correlates well with weeks of gestation between 20-31 weeks. LIMITATION: - inaccurate in women with obesity, polyhydramnios and uterine fibroids. ESTIMATING GESTATIONAL AGE BY MCDONALD’S RULE - This knowledge is exceedingly vital in the event of a high-risk pregnancy. PROCEDURE: 1. Explaining the procedure to the client. 2. Have the woman void. 3. Measure the fundal height (FH) using McDonald’s Method ( from the symphysis pubis to the top of the fundus ). 4. Compute using the McDonald’s Rule :  a. Duration of pregnancy in lunar months : FH in cm x 2 divided by 7 b. Duration of pregnancy in weeks : FH in cm x 8 divided by 7 example : FH : 34 cm 34 x 8 = 272 272 / 7 = 38 – 39 weeks ASSESSIN G Fetal well-being C. Assessing Fetal Well-Being 1. Fetal movement – a. Sandovsky method : felt by the mother ( quickening ) begins approximately 18 to 20 weeks of pregnancy and peaks at 28 to 38 weeks. - a healthy fetus moves at least 10x/day. how to assess fetal movement: * let the mother lie in recumbent position after a meal * record how many fetal movements she feels over the next hour. ( min. twice every 10 min or an average of 10-12 x/hour) * if less than 10 movements let the mother repeat the test for the next half hour. * if still less within two hours – call hlth care provider another protocol …. b. Cardiff method ( count-to-Ten) * the mother records the time interval it takes for her to feel 10 fetal movements. Usually, this occurs within 60 minutes. 2. Fetal Heart Rate ( FHR ) FHR beat - 120 to 160 per minute whole pregnancy - can be heard and counted as early as 10th to 11th week of pregnancy by doppler tech. - fetal heart rate of less than 90 bpm is high risk for miscarriage at 5 to 8 weeks of pregnancy  Variability is categorized as: a. Absent ( none apparent) b. Minimal ( extremely small fluctuations) c. Moderate ( amplitude range of 6-25 beats per minute ) d. Marked ( amplitude range over 25 beats)   If a 20-minute period passes without any fetal movement, it may mean only that the fetus is sleeping. If the mother is given an oral carbohydrate snack, such as orange juice, her blood glucose level may increase enough to cause fetal movement. 11. Triple Screening - or analysis of three indicators ( MSAFP, unconjugated estriol, and hCG) - done to yield even more reliable results. 12. Chorionic Villi Sampling - a biopsy and chromosomal analysis of chorionic villi that is done at 10 to 12 weeks of pregnancy. 14. Percutaneous Umbilical Blood Sampling - the aspiration of blood from the umbilical vein for anaylsis. - if fetus is found to be anemic, blood may be transfused using the same procedure. 15. Amnioscopy - the visual inspection of the amniotic fluid through the cervix and membranes with an amnioscope ( a small fetoscope ). - use to detect meconium staining.  16. Fetoscopy - fetus is visualized by inspection through a fetoscope ( an extremely narrow, hollow tube inserted by amniocentesis technique). -used for the following purposes: * to confirm the intactness of the spinal column. * to obtain biopsy samples of the fetal tissue and fetal blood samples * to perform elemental surgery  17. Biophysical Profile - combines five parameters ( fetal reactivity, fetal breathing movements, fetal body movement, fetal tone, and amniotic fluid volume) into one assessment.