Prenatal Care and Nutrition
Dating, visits, labs, supplements and warning signs
Dating the pregnancy
- Naegele's rule: first day of last menstrual period + 7 days − 3 months + 1 year.
- Early ultrasound (crown–rump length) is the most accurate dating.
- Fundal height: 12 wk at the symphysis; ~20 wk at the umbilicus; from 20–36 wk, height in cm ≈ weeks (±2 cm).
- Preterm <37 0/7 wk · early term 37 0/7–38 6/7 · full term 39 0/7–40 6/7 · late term 41 0/7–41 6/7 · post-term ≥42 0/7.
GTPAL
Gravida (pregnancies) · Term births · Preterm births · Abortions/miscarriages (<20 wk) · Living children. Twins count as one pregnancy and one birth.
Supplements and diet
| Folic acid | 400 mcg (0.4 mg) daily, starting ≥1 month before conception; 4 mg after a previous neural tube defect |
| Iron | 27 mg/day (prenatal vitamin); more if anemic |
| DHA (omega-3) | 200–300 mg/day (milligrams, not micrograms) or 2–3 servings of low-mercury fish/week |
| Calcium | 1,000 mg/day (1,300 mg for teens) |
| Calories | No extra in 1st trimester; ~+340/day 2nd; ~+450/day 3rd |
Avoid: alcohol (no safe amount), smoking, unpasteurized dairy and deli meats (Listeria), raw meat and cat litter (toxoplasmosis), high-mercury fish (shark, swordfish, king mackerel, tilefish, bigeye tuna, marlin); caffeine <200 mg/day.
Typical prenatal timeline
| When | What |
|---|---|
| First visit | Blood type, Rh and antibody screen, CBC, rubella and varicella immunity, HIV, syphilis, hepatitis B and C, urine culture, Pap/HPV if due; offer genetic screening |
| 10–14 weeks | Cell-free DNA (from 10 wk) and/or nuchal translucency screening (offered) |
| 15–22 weeks | Maternal serum AFP (neural tube defects); anatomy ultrasound ~18–22 wk |
| 24–28 weeks | Glucose screen for gestational diabetes; CBC; antibody screen if Rh-negative |
| 28 weeks | Rh immune globulin if Rh-negative and unsensitized |
| 27–36 weeks | Tdap every pregnancy (ideally early in this window); RSV vaccine at 32–36 wk during September–January (or infant antibody after birth) |
| 36 0/7–37 6/7 weeks | Group B strep vaginal–rectal culture |
Influenza and COVID-19 vaccines can be given in any trimester. Live vaccines (MMR, varicella) are not given in pregnancy. Visit frequency: every 4 weeks to 28 wk, every 2 weeks to 36 wk, then weekly.
Normal changes
- Blood volume ↑ 40–50% → physiologic anemia (Hgb <11 g/dL in 1st/3rd trimester or <10.5 in 2nd is anemia).
- HR ↑ 10–15/min; BP dips in 2nd trimester.
- Supine hypotension: uterus compresses the vena cava → place on her left side (or wedge under right hip).
- hCG maintains the corpus luteum (and progesterone) early in pregnancy. It's the hormone pregnancy tests detect. It does not feed the fetus.
Teach: report right away
Vaginal bleeding · gush or leak of fluid · severe headache, vision changes, RUQ/epigastric pain, sudden swelling of face or hands · decreased fetal movement · regular contractions before 37 weeks · fever or painful urination · persistent vomiting · thoughts of self-harm.