FM Prenatal Care

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Prenatal Care

  • Date the pregnancy = LMP start date – 3 months + 7 days. Refer to a high-risk provider if diabetes, asthma, thyroid disease, HTN, lupus, thromboembolism, seizures
  • Ultrasound is not mandatory only truly need it to evaluate uncertain gestational age, size/date differences, vaginal bleeding, multiple gestations, placental location, and other high-risk situations.
  • Ultrasound dating is accurate within 1 week if performed in 1st trimester, w/in 2 weeks in 2nd trimester, 3 weeks in 3rd trimester.
  • Prenatal visits: every 4 weeks through week 28, then every 2 weeks through week 36, then weekly.

First prenatal care visit

  • CBC. Repeat at 28 weeks if at risk of anemia. If Hgb < 10.5, risk of preterm delivery, low fetal iron stores, might have thalassemia. Treat mild anemia w/ iron. Moderate – check ferritin and Hb electrophoresis.
  • Tests at every visit: weight, BP, fundal height, fetal heart tones w/ Doppler, urinalysis for protein, glucose, and infection.
    • Screen for gestational diabetes at 24 to 28 weeks, unless very low risk.
      • Start w/ 1 hour 50g glucose challenge – abnormal if > 140. If positive, 3 hr glucose tolerance test – get fasting, 1 hr, 2 hr, and 3 hr values. Positive if 2/4 are positive.
    • Induce between 41 and 42 weeks.

Disease Testing

  • Hep B surface antigen
    • – if +, check LFTs and hepatitis serology to determine active hepatitis vs. chronic carrier. Baby will need Hep B immune globulins and Hep B vaccination.
  • HIV ELISA and follow with PCR or western blot.
    • If positive, offer anti-HIV meds, elective cesarean, and IV zidovudine during labor → reduce transmission from 25% to 2%.
  • Syphillis
    • w/ rapid plasma reagin (RPR), then specific antibody test like MHA-TP if positive. Must stage the disease. Repeat at 28 weeks if at risk.
  • PAP smear for gonorrhea (blindness, preterm delivery – treat w/ ceftriaxone) and chlamydia (blindness, pneumonia
    • – treat w/ azithromycin or amoxicillin).
    • If ASC-US – repap postpartum, LGSIL or HSIL → colposcopy
  • Group B strep
    • – culture lower vagina, rectum, and perineal area at 35-37 weeks. 10-30% are positive.
    • Treat w/ IV penicillin at the time of labor or rupture of membranes to reduce GBS infection
    • – if not available, can
      • use IV ampicillin.
      • If allergic to penicillin can do cephalothin, erythromycin, clindamycin, and vancomycin.
      • If bacteriuria, give abx during pregnancy.
  • Rubella antibody – if not immune, vaccinate after delivery.
  • Urinalysis + culture
    • to look for asymptomatic bacteriuria (100k+ bugs/mL)
    • – increased risk of pyelonephritis, preterm birth, low birth weight. Must treat.

Immunity testing

  • Blood type and Rh status. If Rh-negative, follow with antibody screen (indirect Coombs test). Lewis lives, Kell kills, Duffy dies
    • If negative, there is no isoimmunization. Give Rho(D) immune globulin at 28 weeks, at delivery, and if any risk of 1 mL of blood mixing – trauma, bleeding, CVS, amniocentesis, etc. Can give before 12 weeks if threatened abortion.
      • Otherwise, first pregnancy will make IgM antibodies – do not cross the placenta, so no risk to the baby.
      • Later pregnancies will take place with IgG → do cross placenta.
      • Risk of extravascular hemolysis in the baby
        • (1) elevated BR and risk of kernicterus;
        • (2) anemia → high output heart failure and myocardial ischemia;
        • (3) extramedullary hematopoiesis → decreased liver production of plasma proteins → decreased oncotic pressure → ascites, pericardial effusion, pleural effusion, subcutaneous edema.
    • If positive antibody screen and it’s confirmed as Rh (anti-D),
      • then assess titer to learn fetal effect.
      • Low titer → observe, high titer → further testing w/ ultrasound (look at Middle Cerebral Artery velocity – increased with anemia) and maybe amniocentesis.
    • Screen for other RBC antibodies:
      • Lewis doesn’t cross the placenta, Kell suppresses erythropoiesis.”
      • Lewis lives, Kell kills”

Genetic screening for trisomies

  • 1st trimester:
    • Ultrasound for nuchal translucency.
    • At 10-13 weeks, can add hCG & PAPP-A (pregnancy-associated plasma protein)
  • 2nd trimester during weeks 15-20:
    • Triple screen = hCG, AFP, estriol. 95% specific, but higher false-negative rate – approximately 65% sensitive.
    • Quadruple screen = hcg, AFP, estriol + inhibin A. 95% specific, quadruple is 80% sensitive.
  • Increased risk of aneuploidy if mom is > 35 yrs w/ singleton or > 32 yrs with multiples. Offer:
    • 10-12 weeks: CV sampling with AFP testing. Has 1-1.5% risk of miscarriage, risk of limb deformity is 1 in 1000 to 1 in 3000
    • 15+ weeks: amniocentesis. Has 0.5% risk of miscarriage.


  • Vitamins: Should take 400-800 micrograms of folic acid.
  • DM or Epilepsy → 1 mg. Epileptics should continue to take anticonvulsant meds, but might change type. Eg., valproic acid has a high risk of neural tube defects.
  • Previous neural tube defect → 4 mg.


  • Can give killed influenza and tetanus during pregnancy.
  • Do not give varicella, rubella, or live influenza during pregnancy.

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