Fetal Development, Screenings, and Diagnostics

FETAL DEVELOPMENT 9 weeks- Delivery Fetal Maturation ◦ Period of refinement for structure & function. ◦ Viability defined as ability for a fetus to survive outside the uterus. ◦ Defined by fetal weight & pregnancy duration. ◦ Definition of viability varies by state. ◦ Threshold is between 22-25 weeks. Placental Roles ◦ Week 10 ◦ Takes over production of progesterone & secretes copious amounts. ◦ Week 11 ◦ Produces enough progesterone and estrogen to maintain pregnancy. ◦ Metabolic and nutrient exchange between fetal and maternal circulations. ◦ Placental functions: oxygenation, nutrition, and excretion. Umbilical Cord ◦ 2 umbilical arteries: ◦ Carry waste and deoxygenated blood away from fetus. ◦ 1 umbilical vein: ◦ Carries oxygenated blood from placenta to fetus. ◦ Covered in Wharton’s Jelly: ◦ Special connective tissue surrounds for cushioning. Fetal Circulation ◦ https://www.youtube.com/watch?v=-IRkisEtzsk ◦ Most circulating blood is shunted away from the lungs via 3 shunts. ◦ Ductus Venosus ◦ Constricts when umbilical cord blood flow stops. ◦ Foramen Ovale ◦ Closes when infant breathes. ◦ Ductus Arteriosus ◦ Constricts as arterial 02 rises. Review of Systems Hematopoietric Respiratory ◦ Antigenic factors that determine blood type are present around week 6. ◦ Weeks 3-17: ◦ Rh- moms are at risk for isoimmunization for any pregnancy >6 weeks gestation. ◦ Weeks 16-24: ◦ Respiratory track develops. ◦ Bronchi, vascular structures, & primitive alveoli formed. ◦ 24 weeks- term: ◦ Alveoli mature & begin to secrete surfactant. ◦ > 32 weeks: ◦ Sufficient surfactant levels present; > chance of survival. Review of Systems Gastrointestinal ◦ 18-22 weeks: Hepatic ◦ Bile will help form meconium. ◦ Amniotic fluid swallowed by fetus. ◦ 1st stool called meconium. ◦ 26-30 weeks: ◦ Brown fat development starts. ◦ 36 weeks: ◦ Ready to “go.” ◦ Lack of vitamin K + the gut being sterile = inability to synthesize coagulation factors. ◦ Why we administer I.M Vitamin K @ delivery. Review of Systems Renal ◦ 5th week: ◦ Kidneys formed. Neurologic ◦ 4th week: ◦ Neural tubes formed *Why preconception Folic Acid is so important. ◦ 9th week: ◦ Functional. ◦ Fetal stressors can cause long term CNS damage. ◦ Stressors: ◦ Fetal urine contributes to amniotic fluid index. ◦ Poor nutrition, drugs, environmental exposures, hypoxia. ◦ Damage: ◦ Cerebral palsy, learning & intellectual disabilities, neuromuscular impairment. Review of Systems Endocrine ◦ 12th week: ◦ Islets of Langerhans develop. ◦ 20th week: ◦ Insulin produced. ◦ Maternal hyperglycemia = Fetal hyperglycemia which results in fetal hyperinsulinemia . ◦ Macrosomia ◦ Blocks lung maturation Reproductive ◦ XY = Male ◦ 28th week testes descend. ◦ XX= Female ◦ 16th week oogenesis established. ◦ Pseudomenstruation ◦ External genitalia well defined by 12 th week. ◦ Maternal estrogen can cause mammary glad engorgement in both sexes. ◦ May leak “witch’s milk” as newborn Review of Systems Musculoskeletal ◦ Defects in bony fusion can cause forms of spina bifida. ◦ Sutures & Fontanels ◦ Adaptations in the skull which allow for head to mold in birth canal. ◦ Weeks 11-12: ◦ Practice breathing begins. ◦ Weeks 16-20: ◦ Fetal movement felt by mother. ◦ Called “quickening” Integumentary ◦ Skin is very thin and wrinkled with visible vascularity ◦ Around 32 weeks subcutaneous fat builds & fetus becomes “plumper.” ◦ Mechanisms of protection ◦ Lanugo: ◦ Fine hair. ◦ Vernix Caseosa: ◦ White, greesy, cheesy like substance. Visual Aids Lanugo Vernix Caseosa Review of Systems Passive Acquired Immunity ◦ Mother to fetus during pregnancy via placenta. Passive Immunity ◦ Mother to newborn who is breastfed. SCREENINGS & DIAGNOSTICS BIOCHEMICAL Maternal Serum Testing ◦ Noninvasive prenatal testing (NIPT) ◦ A.K.A: Cell-Free Fetal DNA. ◦ Extracts fetal DNA from maternal blood sample. ◦ Identifies chromosomal abnormalities. ◦ Maternal serum alpha-fetoprotein (MSAFP) ◦ Screening tool for neural tube defects. ◦ Preformed between 15-20 weeks ◦ Ideally between 16-18 weeks. Chorionic Villi Sampling (1st Trimester) Amniocentesis Procedure (2nd or 3rd Trimester) Amniocentesis Results Alpha-fetalprotein ◦ Diagnostic Fetal Lung Maturity ◦ Lecithin/Sphingomyelin (L/S): ◦ Results as ratio (2:1 = maturity) ◦ High levels: ◦ Neural tube defects ◦ Anencephaly ◦ Spina Bifida ◦ Omphalocele ◦ Low levels: ◦ Chromosomal disorders ◦ Phosphatidylglycerol (PG): ◦ Lower the level- the higher incidence of respiratory distress Percutaneous Umbilical Cord Sampling (PUBS) ◦ Aspiration of fetal blood from the umbilical cord (directly from the fetal circulation) ◦ Done under U/S guidance ◦ Maternal-fetal bleeding risks ◦ Usually used after C.V.S or amnio results detected an anomaly in the fetus. ◦ Chromosome mutation diagnosis, assessment for fetal anemia, infections, or thrombocytopenia. ◦ Transfusions for Rh disease or hydrops fetalis treatment BIOPHYSICAL Fetal Movement ◦ 1st line of Surveillance= Fetal movement! ◦ Advantages: ◦ Inexpensive ◦ Non-invasive ◦ Convenient ◦ Disadvantages: ◦ Maternal perception of movement may vary. ◦ Time of day may affect movement (sleep). Ultrasounds ◦ Standard ◦ Fetal presentation ◦ Amniotic Fluid Index (volume) a.k.a A.F.I ◦ Placental position ◦ Growth parameters ◦ 20-week anatomy scan ◦ Limited ◦ Looking for specific parameter or piece of information. ◦ Specialized ◦ Comprehensive examination using specialized equipment. ◦ Used to visualize suspected birth defect/anomaly. ◦ Table 26.1 (pg. 570) Oligohydramnios • Less than 500 mL of A.F. • Dx. between 32-36 weeks gestation. A.F.I Abnormalities • Related to poor pregnancy outcomes Polyhydramnios • Greater 2,000 mL of A.F • Dx. between 32-36 weeks gestation. • Several causes: • Maternal diabetes • Fetal anomalies • Idiopathic Biophysical Profile (B.P.P) ◦ Reliable predictor of fetal well-being. ◦ Detailed assessment of physical & physiological characteristics. ◦ Tables 26.2 & 26.3 explain categories/ scoring. ◦ Pg. 572 Variable Criteria Score Fetal Breathing Movement >/= 30 secs in 30 min < or absent 2 0 Gross Body Movements >/= 3 movements <3 movements 2 0 Tone 1 episode of full extension/flexion Low/lack/absent episode 2 0 A.F.I >/ = 2 2cm pockets < 2 cm or absent 2 0 FHR Reactive NST Nonreactive 2 0 Biophysical Profile Grading Scheme FETAL MONITORING Nonstress test ◦ Woman placed on E.F.M for 20 minutes ◦ Fetus needs x 2 episodes of: ◦ 15 x 15 accelerations for >32 weeks ◦ 10 x10 accelerations for < 32 weeks ◦ Charted as Reactive vs. Nonreactive ◦ Figures 26.9 & 26.10 ◦ Pgs.: 579-580 ◦ Nonreactive requires follow up ◦ Follow up is typically a B.P.P. Interpreting NST: Baseline ◦ FHR baseline is the average rate during a 10-minute period. ◦ Baseline is identified over 2 minutes of data. ◦ Bradycardia ◦ FHR below 110 bpm ◦ Associated with fetal cardiac problem or structural defect, viral infections, maternal hypoglycemia or hypothermia ◦ Tachycardia ◦ FHR above 160 bpm. ◦ Often caused by maternal fever/infection or fetal anemia, can be in response to some meds or illicit drugs Interpreting NST: Variability -Fluctuation of the fetal heart rate (not including accelerations or decelerations) – ask yourself: how squiggly is the line? ** most important indicator of adequate fetal oxygenation ** -Moderate variability = reliable predictor of normal fetal acidbase balance -Causes of decreases/minimal variability in fetal heart rate variability • Sleep cycle • Early gestational age • Medications causing CNS depression (ie: MgSO4, opioids) • Fetal anomalies Interpreting NST: Accelerations • Increase in FHR above the baseline • 15 x 15 or 10 x 10 depending on GA • Indicative of a well-oxygenated fetus a.k.a: oxytocin challenge test (OCT) ◦ Contractions started by either nipple stimulation or oxytocin infusion. ◦ Challenge lasts 10-20 minutes. ◦ Desired result is a negative test. ◦ Negative results are associated with positive fetal outcomes.