Obstetrics and Prenatal Care for FNP Boards: Labs, Complications, and Postpartum
Clinical High-Yield · 10 min read · April 28, 2026
Obstetrics and prenatal care is a consistently tested section on the FNP boards, and it rewards organized, systematic preparation. The boards test a predictable set of content: the prenatal lab schedule, the management of gestational diabetes and preeclampsia, and the essentials of postpartum care. Here's the high-yield content organized by trimester.
First Trimester: Initial Prenatal Visit
The initial prenatal visit (ideally at 8–10 weeks) includes a comprehensive lab panel. Know which tests are done and why.
Routine first-trimester labs:
- Blood type and Rh factor (with antibody screen)
- CBC (anemia, thrombocytopenia)
- Rubella immunity (IgG)
- Varicella immunity (IgG)
- Hepatitis B surface antigen (HBsAg)
- HIV (opt-out screening)
- Syphilis (RPR or VDRL)
- Gonorrhea and chlamydia (NAAT)
- Urine culture (asymptomatic bacteriuria — treat in pregnancy)
- Pap smear (if due)
- Thyroid function (TSH) — if symptomatic or high-risk
- First-trimester screening: nuchal translucency ultrasound + PAPP-A + free β-hCG (screens for trisomy 21, 18, 13)
Rh sensitization: Rh-negative women with an Rh-positive partner receive RhoGAM (Rh immunoglobulin) at 28 weeks and within 72 hours of delivery. Also given after any potentially sensitizing event: miscarriage, ectopic pregnancy, amniocentesis, abdominal trauma.
Folic acid: 400–800 mcg/day starting at least 1 month before conception and continuing through the first trimester prevents neural tube defects. Women with a prior NTD-affected pregnancy take 4 mg/day.
Medications to avoid in pregnancy: The boards test teratogens. Key ones: isotretinoin (severe birth defects — requires iPLEDGE program), valproate (neural tube defects), ACE inhibitors (fetal renal dysplasia in 2nd/3rd trimester), warfarin (embryopathy in 1st trimester, fetal hemorrhage in 3rd trimester), tetracyclines (tooth discoloration), fluoroquinolones (cartilage damage — avoid), methotrexate (abortifacient and teratogen).
Second Trimester: Screening and Anatomy
15–20 weeks: Quad screen (maternal serum AFP, hCG, estriol, inhibin A) screens for trisomy 21, trisomy 18, and neural tube defects. AFP interpretation: elevated AFP → neural tube defect or abdominal wall defect; decreased AFP → trisomy 21 or 18.
18–20 weeks: Anatomy ultrasound — evaluates fetal anatomy, placental location, amniotic fluid volume, and fetal growth.
Amniocentesis: Offered to women ≥35 years (advanced maternal age) or those with abnormal screening. Performed at 15–20 weeks. Diagnoses chromosomal abnormalities, NTDs (elevated AFP in amniotic fluid), and some genetic disorders.
Board Pearl: The boards test the difference between screening tests (which give a risk estimate) and diagnostic tests (which give a definitive answer). Nuchal translucency + PAPP-A + free β-hCG is a screening test. Amniocentesis and CVS (chorionic villus sampling) are diagnostic tests.
Third Trimester: GDM, GBS, and Preeclampsia
Gestational Diabetes Mellitus (GDM): Screening at 24–28 weeks with a 1-hour 50g glucose challenge test (GCT). A value ≥140 mg/dL (some use ≥130 mg/dL) is positive and requires a 3-hour 100g oral glucose tolerance test (OGTT) for diagnosis. GDM is diagnosed if 2 or more values on the OGTT are elevated. Management: dietary modification first, then insulin if glucose targets are not met (metformin and glyburide are used but are not FDA-approved for GDM).
Group B Streptococcus (GBS) screening: Vaginal-rectal swab culture at 35–37 weeks. GBS-positive women receive IV penicillin G during labor (ampicillin if penicillin-allergic without anaphylaxis history; clindamycin or vancomycin for high-risk penicillin allergy). Untreated GBS can cause neonatal sepsis, meningitis, and pneumonia.
Preeclampsia: New-onset hypertension (BP ≥140/90 on two occasions ≥4 hours apart) after 20 weeks gestation, with proteinuria (≥300 mg/24 hours or protein:creatinine ratio ≥0.3) or other end-organ damage. Risk factors: nulliparity, obesity, multiple gestation, prior preeclampsia, chronic hypertension, diabetes, renal disease.
Severe features of preeclampsia: BP ≥160/110, thrombocytopenia (<100,000), renal insufficiency (creatinine >1.1), impaired liver function (LFTs >2× normal), pulmonary edema, new-onset headache unresponsive to medication, visual disturbances.
Management: Definitive treatment is delivery. For severe preeclampsia <34 weeks, expectant management with close monitoring may be considered in a hospital setting. Magnesium sulfate is given for seizure prophylaxis (eclampsia prevention) and for fetal neuroprotection if delivery is anticipated before 32 weeks. Antihypertensives for BP ≥160/110: labetalol IV, hydralazine IV, or nifedipine PO.
Postpartum Care: The 6-Week Visit and Beyond
The postpartum visit is traditionally at 6 weeks, though ACOG now recommends an initial contact within 3 weeks and a comprehensive visit by 12 weeks.
Postpartum depression (PPD): Affects 10–15% of women. The Edinburgh Postnatal Depression Scale (EPDS) is the standard screening tool. PPD is distinguished from the "baby blues" (mild mood changes resolving within 2 weeks) by its persistence and severity. Treatment: SSRIs are first-line (sertraline and paroxetine have the most data for safety in breastfeeding). Postpartum psychosis (rare, 1–2/1000) is a psychiatric emergency — hallucinations, delusions, confusion — requires immediate hospitalization.
Breastfeeding: Exclusive breastfeeding is recommended for the first 6 months. Contraindications to breastfeeding: HIV (in resource-rich settings), active TB (until treated), galactosemia (in the infant), certain medications (chemotherapy, radioactive iodine, ergotamine).
Contraception postpartum: Progestin-only methods (mini-pill, Depo-Provera, Nexplanon, Mirena) are safe for breastfeeding women. Combined estrogen-progestin methods should be avoided for the first 6 weeks postpartum due to increased VTE risk, and used with caution in breastfeeding women.
The Bottom Line
OB on the FNP boards rewards knowing your prenatal lab schedule by trimester, your GDM screening protocol, your GBS management, and your preeclampsia criteria. Know your teratogens. Know the Edinburgh scale for PPD. Know your postpartum contraception options. Master these and OB becomes one of your most reliable sections.
→ Explore the FNP Board Review Book — every OB and women's health topic covered with board-focused clinical pearls.