Episode Details

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Fetal Development & Physiology occurs in three stages: the preembryonic stage (fertilization to 2nd week), embryonic stage (end of 2nd week to 8th week), and fetal stage (end of 8th week to birth). The embryonic stage is the critical period of organ differentiation, making the embryo highly susceptible to teratogens (drugs, alcohol, or infections causing physical defects). Fetal support systems include amniotic fluid, which maintains temperature, cushions the fetus, and allows symmetric growth. The umbilical cord contains two arteries (carrying deoxygenated blood and waste away from the fetus) and one vein (carrying oxygenated blood to the fetus). The placenta facilitates nutrient and gas exchange via diffusion; it acts as a pass-through, meaning almost everything the pregnant person ingests reaches the fetus. Fetal circulation relies on three shunts (ductus venosus, ductus arteriosus, foramen ovale) to bypass the lungs and liver, directing highly oxygenated blood directly to vital organs.

Assessment of Fetal Well-Being relies on key diagnostic procedures:

• Ultrasounds: Abdominal ultrasounds require a full bladder to displace the uterus. Transvaginal ultrasounds are invasive and do not require a full bladder.
• Biophysical Profile (BPP): Combines ultrasound and nonstress testing to measure five variables (FHR, breathing, gross body movements, fetal tone, amniotic fluid). A normal, healthy score is 8 to 10.
• Nonstress Test (NST): A reactive (normal) result shows the fetal heart rate accelerating at least 15 beats per minute for 15 seconds, twice in a 20-minute period.
• Contraction Stress Test (CST): Evaluates fetal response to labor contractions. A negative (normal) CST shows no late decelerations, while a positive (abnormal) CST shows late decelerations, strongly indicating uteroplacental insufficiency.
• Amniocentesis: Aspiration of amniotic fluid to measure Alpha-fetoprotein (AFP) (high levels indicate neural tube defects; low levels indicate Down syndrome) and assess fetal lung maturity (an L/S ratio of 2:1 is normal).

Maternal Nutrition is vital. Clients with a normal BMI should gain 25 to 35 lbs total (2 to 4 lbs in the first trimester, then ~1 lb/week). Caloric intake increases by 340 calories/day in the 2nd trimester and 452 calories/day in the 3rd trimester. Critical nutrients include folic acid (600 mcg/day) to prevent neural tube defects, iron (best absorbed with vitamin C between meals), and calcium (1,000 mg/day). Pregnant clients should restrict caffeine to <300 mg/day and completely avoid alcohol. Clients with maternal phenylketonuria (PKU) must strictly avoid high-protein foods and aspartame 3 months prior to and during pregnancy to prevent fetal intellectual disability.