The FM Prenatal Care is part of the Family Medicine section provides High Yield information for the USMLE, COMLEX, Medical School, Residency, and in the future career as a Physician. Prepare and Learn Ahead! Educating, Preparing, and Proving high-yield content, quizzes, and medical resources to students who are interested in the medical field.
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.
- Screen for gestational diabetes at 24 to 28 weeks, unless very low risk.
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”
- 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.
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
- 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.
Vaccinations
- Can give killed influenza and tetanus during pregnancy.
- Do not give varicella, rubella, or live influenza during pregnancy.