Chapter 9: Normal Pregnancy and Care of Developing Fetus PDF

THE GROWING FETUS  STAGES OF FETAL DEVELOPMENT  1. F E RT IL IZAT I ON a. Equal maturation of both sperm and ovum b. Ability of the sperm to reach the ovum c. Ability of the sperm to penetrate the zona pellucida and cell membrane Functional Ovum: 24-48 ho...

THE GROWING FETUS  STAGES OF FETAL DEVELOPMENT  1. F E RT IL IZAT I ON a. Equal maturation of both sperm and ovum b. Ability of the sperm to reach the ovum c. Ability of the sperm to penetrate the zona pellucida and cell membrane Functional Ovum: 24-48 hours Functional Sperm: 48-72 hours Successful: 72 hours  2. IMPL ANTATION usually occurs high in the uterus on the posterior surface. If the point of implantation is low in the uterus, the growing placenta may occlude the cervix and make birth of the child difficult (placenta previa) because the placenta can block the birth canal  Serves as a buffer against injury After penetration 32 cells of 23 chromosomes ovum and 23 chromosomes sperm Mitotic cell division 16-50 cells occurs  TERM USED TO DENOTE FETAL GROWTH Name Time Period Ovum From ovulation to fertilization Zygote From fertilization to implantation Embryo From implantation to 5-8 weeks Fetus From 5-8 weeks until term Conceptus Developing embryo or fetus and placenta structures throughout pregnancy 3. EMBRYONIC AND FETAL STRUCTURES  A. THE DECIDUA Uterine endometrium to continue to grow in thickness and vascularity instead of sloughing off as in a usual menstrual cycle  B. CHORIONIC VILLI: 11th to 12th day Reach out from throphoblast cells into the endometrium to begin formation of the placenta. Central Core: Connective tissues and cappiliaries and produces placental hormones Middle Layer: Langhans layer  C. THE PL ACENTA: Grows from a few identifiable trophoblastic cells at the beginning of pregnancy to an organ 15 to 20 cm in diameter and 2 to 3 cm in depth, covering about half the surface area of the internal uterus at term placenta provides nutrients to and removes wastes from the fetus from the third month of pregnancy until birth. The placenta is formed from the chorion, its chorionic villi, and the adjacent decidua basalis.  D. CIRCUL ATION: 12th day: maternal blood begins to collect in the intervillous spaces of the uterine endometrium surrounding the chorionic villi. 3rd week: O2 and other nutrients are transported to the embryo Uteroplacenta blood flow: 50ml/min to 500-600ml/min at term The uteroplacental circulation carries oxygenated arterial blood from the maternal circulation to the intervillous spaces—large spaces separating chorionic villi in the placenta. B Heart rate and Cardiac output increases Placenta weighs 400-600g (smaller vs bigger placenta)  ENDOCRINE FUNCTION 1. Human Chorionic Gonadotropin: Fail-safe measure to ensure the corpus luteum of the ovary continues to produce progesterone and estrogen so the endometrium of the uterus is maintained. Suppressing the maternal immunologic response so placental tissue is not detected and rejected as a foreign substance. 2. Progesterone: necessary to maintain the endometrial lining of the uterus during pregnancy 3. Estrogen: contributes to the woman’s mammary gland development in preparation for lactation and stimulates uterine growth to accommodate the developing fetus. 4. Human Placental Lactogen (Human Chorionic Somatomammotropin) hPL is a hormone with both growth- promoting and lactogenic Serves the important role of regulating maternal glucose, protein, and fat levels so adequate amounts of these nutrients are always available to the fetus.  AMNIOTIC MEMBRANES A dual-walled sac with the chorion as the outmost part and the amnion as the innermost part A M N I O T I C F LU I D Term: 800-1200ml Purpose: shield the fetus against pressure or a blow to the mother’s abdomen protects the fetus from changes in temperature muscular development protects the umbilical cord from pressure Hydramnios (more than 2,000 ml in total or pockets of fluid larger than 8 cm on ultrasound) oligohydramnios or a reduction in the amount of amniotic fluid. Amniotic fluid: 7.2 (alkaline) Vs Urine: 5.0 to 5.5 (acidic)  UMBILICAL CORD is formed from the fetal membranes, the amnion and chorion, and provides a circulatory pathway that connects the embryo to the chorionic villi of the placenta. Its function is to transport oxygen and nutrients to the fetus from the placenta and to return waste products from the fetus to the placenta. Wharton Jelly 21 inch and 0.75 inch at term One vein (carries blood from placenti villa to fetus), two arteries (carries blood from fetus back to placental villi)- Record Cord Coil (hypocoiling vs hypercoiling)  ORIGIN AND DEVELOPMENT OF ORGAN SYSTMES Following the moment of fertilization, the zygote, which later becomes an embryo and then a fetus, begins to grow at an active pace. 1. Stem Cells- the first 4 days of life, zygote cells are termed totipotent stem cells, or cells so undifferentiated they have the potential to grow into any cell in the human body After 4 days: cells begin to show differentiation or lose their ability to become any body cell pluripotent stem cells VS multipotent 2. Zygote Growth Cephalocaudal P R I M A RY G E R M L AY E R S Body organ systems develop from specific tissue layers called germ layers. At the time of implantation, the blastocyst already has differentiated to a point at which three separate layers of these cells are present: the ectoderm, the endoderm, and the mesoderm 8 weeks gestation (the end of the embryonic period). During this early time of organogenesis (organ formation), the growing structure is most vulnerable to invasion by teratogens CARDIOVASCULAR SYSTEM Cardiovascular System Is the first system to function. Simple blood cells joined to the walls of the yolk sac progress to become a network of blood vessels and a single heart tube, which forms as early as the 16th day of life and beats as early as the 24th day  FETAL CIRCUL ATION Differs from extrauterine circulation because the fetus derives oxygen and excretes carbon dioxide not from gas exchange in the lungs but from exchange in the placenta.  FETAL HEMOGLOBIN It has a different composition (two α and two γ chains compared with two α and two β chains of adult hemoglobin). HbF is a form of haemoglobin which has a stronger oxygen affinity than adult hemoglobin, this increases oxygen transport to the fetus within the uterus by capturing oxygen from the placental vasculature which has much lower oxygen tension than in the lungs. R E S P I RAT O RY S Y S T E M Other important respiratory developmental milestones include: Spontaneous respiratory practice movements begin as early as 3 months gestation and continue throughout pregnancy. 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 shortly after birth. Surfactant (Lecitin and sphingomyelin)-, a phospholipid substance, is formed and excreted by the alveolar cells of the lungs beginning at approximately the 24th week of pregnancy. This decreases alveolar surface tension on expiration, preventing alveolar collapse and improving the infant’s ability to maintain respirations in the outside environment at birth. Check for Fetal lung maturity; bethametasone  NERVOUS SYSTEM A neural plate (a thickened portion of the ectoderm) is apparent by the third week of gestation. The top portion differentiates into the neural tube, which will form the central nervous system (brain and spinal cord), and the neural crest, which will develop into the peripheral nervous system. All parts of the brain (cerebrum, cerebellum, pons, and medulla oblongata) form in utero, although none are completely mature at birth. Brain growth continues at high levels until 5 or 6 years of age. By 24 weeks, the ear is capable of responding to sound, and the eyes exhibit a pupillary reaction, indicating sight is present. DIGESTIVE SYSTEM Forms during the 4th week – fetus begins to swallow amniotic fluid during second trimester. Atresia Rapid intestinal growth by 6th wk: Omphalocele and Gastrochisis Meconium: is a sterile, dark greenish brown, semisolid residue of bile and embryonic secretions plus cellular waste (epithelial tissue) and hair swallowed in utero. Presence of meconium in amniotic fluid before delivery usually indicates fetal hypoxia Check for passage of Meconium Hypoglycemia and hyperbilirubenia-liver function is still immature  ENDOCRINE SYSTEM Fetal pancreas produces insulin (insulin don’t cross the placenta) Thyrpid and parathyroid glands: metabolic function and calcium balance  MUSCULOSKELETAL SYSTEM Bones and muscles are developed from mesoderm by 4 th week. Muscle contract spontaneously by 7th week and can be seen to move in utz as early as 11th week.  REPRODUCTIVE SYSTEM Can be determined as early as 8 weeks or 10 weeks Wolfian or Mullerian duct Born with undescended testes  URINARY SYSTEM Urine is formed on the 12th week and excreted into amniotic fluid by 16th week of gestation. Fetal urine: 500ml/day  INTEGUMENTARY SYSTEM 36 weeks: subcutaneous fat begins to deposited underneath Lanugo and Vernix caseosa present at birth  IMMUNE SYSTEM The immunoglobulin that crosses the placenta from maternal antibodies is IgG 20th-24thweek (passive acquired immunity). Temporary passive immunity against: Polio, rubella, rubeola, diptheria, mumps, hep b and pertusis  https://www.youtube.com/watch? v=EhUOkTPW7L0 ASSESSMENT OF FETAL GROWTH  Health History GDM, HD, Medications, Food Intake, COVID19, Injuries Physical Assessment Weight Aappearance Assessing Fetal Growth and Health Fetal Growth: McDonald's rule is the measurement of the fundal height from the symphysis pubis. Fetal Heart Rate Fetal Movement 10 kicks under 1 hr  In rhythm strip testing, the fetal heart rate is assessed if a good baseline heart rate or a degree of variability is present. The results are categorized as absent (none apparent), minimal (extremely small fluctuations), moderate (a range of 6-25 beats per minute), and marked (range over 25 beats per minute).  A nonstress test monitors an unborn baby's heart rate for 20 to 30 minutes to see if it changes as the fetus moves and during contractions. It is called "nonstress" because doing it places no stress on the fetus. Vibroacoustic Stimulation Acoustic stimulator applied to the abdomen No spontaneous acceleration occurs within 5 mins-apply 1 to 2 sound stimulation.  ULTRASOUND Diagnose pregnancy as early as 6 weeks gestation. Before the procedure: Confirm the presence, size, and Full bladder location of the placenta and amniotic fluid. Prevent hypotension- Establish a fetus is growing and has place towel on the right no gross anomalies such as hydrocephalus; buttock Anencephaly; or spinal cord, heart, Gel shoukl be warm kidney, and bladder concerns. Establish the sex if a penis is revealed. Establish the presentation and position of the fetus. Predict gestational age by measurement of the biparietal diameter of the head or Crown-to- rump measurement. Discover complications of pregnancy To detect a retained placenta or poor uterine involution in the new mother  BIPARIETAL DIAMETER Ultrasonography may be used to predict fetal maturity by measuring the biparietal diameter (side-to-side measurement) of the fetal head.  D OP P L E R PL ACENTAL UM B IL IC AL VE LOC IM E T RY GRADING Placentas can be graded by measures the velocity at ultrasound based on the which red blood cells in particular amount of calcium deposits present in the uterine and fetal the base. vessels travel. Placentas are graded as: 0: between 12 and 24 weeks 1: 30 to 32 weeks 2: 36 weeks 3: 38 weeks (Because fetal lungs are apt to be mature by 38 weeks, a grade 3 placenta suggests the fetus is mature.)  AMNIOTIC NUCHAL FLUID TRANSLUCENC VOLUME Y Between 28 and 40 weeks, the total pockets of amniotic fluid revealed by sonogram average 12 to 15 cm. BIOPHYSICAL PROFILE  MAGNETIC RESONANCE IMAGING A fetal assessment technique because it can identify structural anomalies or soft tissue disorders  MATERNAL SERUM A number of trophoblast cells pass into the maternal bloodstream beginning at about the seventh week of pregnancy Maternal Serum α- Maternal Serum for Fetoprotein Pregnancy-Associated Plasma Protein A AFP is a substance is a protein secreted by produced by the fetal the placenta; liver that can be found low levels in maternal in both amniotic fluid blood are associated with and maternal serum fetal chromosomal (maternal serum α- anomalies, fetoprotein [MSAFP]) (trisomies 13, 18, and 21 Assessed at the 15th or small-for-gestational- week of pregnancy, age (SGA) babies) between 85% and 90% A high PAPP-A level may of neural tube anomalies predict an LGA baby and 80% of babies with Down syndrome can be detected by this method  QUADRUPLE SCREENING Quadruple screening analyzes four indicators of fetal health: AFP, unconjugated estriol (UE; an enzyme produced by the placenta that estimates general well-being), hCG (also produced by the placenta), and inhibin A (a protein produced by the placenta and corpus luteum associated with Down syndrome)  FETAL GENDER Although fetal gender is usually determined by an ultrasound screen at about 4 months, it can be determined as early as 7 weeks by analysis of maternal serum.  INVASIVE FETAL TESTING Amniotic fluid (obtained through amniocentesis, Fig. 9.14) can be analyzed for: AFP Acetylcholinesterase Bilirubin determination. Chromosome analysis. Color. Normal amniotic fluid is the color of water; late in pregnancy, it may have a slightly yellow tinge. A strong yellow color suggests a blood incompatibility (the yellow results from the presence of bilirubin released from the breakdown of red blood cells). A green color suggests meconium staining, a phenomenon Fibronectin: is a glycoprotein that plays a part in helping the placenta attach to the uterine decidua, found in cervical mucous/vagina in later pregnancy as an indicator of preterm labor Inborn errors of metabolism: Examples of illnesses that can be detected in this way are sickle cell disease, cystic fibrosis, muscular dystrophy, Tay-Sachs disease, and maple syrup urine disease (an amino acid disorder)  Lecithin and sphingomyelin are the protein components of the lung enzyme surfactant that the alveoli begin to form at the 22nd to 24th weeks of pregnancy. An L/S ratio of 2:1 is traditionally accepted as lung maturity. Phosphatidylglycerol and desaturated phosphatidylcholine. These are additional compounds, in addition to lecithin and sphingomyelin, found in surfactant. Mature lung function, if they are present in the sample of amniotic fluid, it can be predicted with even greater confidence that respiratory distress syndrome is not likely to occur  PERCUTANEOUS UMBILICAL BLOOD SAMPLING To ensure the blood obtained is fetal blood, it is submitted to a Kleihauer– Betke test, which measures the difference between adult and fetal hemoglobin. If a PUBS test reveals that the fetus is anemic, blood may be transfused into the cord using this same technique An intrauterine transfusion provides blood to an Rh-positive fetus when fetal red blood cells are being destroyed by the Rh-sensitized mother's immune system. This treatment is meant to keep the fetus healthy until the baby is mature enough to be delivered.  FETOSCOPY The use of a fetoscopy, in which the fetus is visualized by inspection through a fetoscope (an extremely narrow, hollow tube inserted by amniocentesis technique), can be yet another way to assess fetal well-being  Confirm the intactness of the spinal column.  Obtain biopsy samples of fetal tissue and fetal blood samples.  Determine meconium staining is not present.  Perform elemental surgery, such as inserting a polyethylene shunt into the fetal ventricles to relieve hydrocephalus or anteriorly into the fetal bladder to relieve a stenosed urethra. It may be possible to repair a neural tube defect such as meningocele or improve the outcome of myelomeningocele by fetoscopy  ASSESSING FETAL WELL-BEING Fetal Movement ▪ Triple Screening Fetal Heart Rate ▪ Chorionic Villi Sampling Ultrasound ▪ Amniocentesis Placental Grading ▪ Lecithin/Sphingomyelin Amniotic Fluid Volume Ration Assessment ▪ Percutaneous Umbillical Electrocardiography Blood Sampling Magnetic Resonance ▪ Amnioscopy Imaging ▪ Fetoscopy Maternal Serum Alpha- Fetoprotein --END--