A 2300-g (5-lb 1-oz) male newborn is delivered to a 29-year-old primigravid woman. The mother has HIV and received triple antiretroviral therapy during pregnancy. Her HIV viral load was 678 copies/mL 1 week prior to delivery. Labor was uncomplicated. Apgar scores are 7 and 8 at 1 and 5 minutes respectively. Physical examination of the newborn shows no abnormalities. Which of the following is the most appropriate next step in management of this infant?

Administer zidovudine, lamivudine and nevirapine

Administer lamivudine and nevirapine

A 28-year-old G1P0 woman at 16 weeks estimated gestational age presents for prenatal care. Routine prenatal screening tests are performed and reveal a positive HIV antibody test. The patient is extremely concerned about the possible transmission of HIV to her baby and wants to have the baby tested as soon as possible after delivery. Which of the following would be the most appropriate diagnostic test to address this patient’s concern?

Polymerase chain reaction (PCR) for HIV RNA

A 23-year-old primigravid woman comes to the physician at 36 weeks' gestation for her first prenatal visit. She confirmed the pregnancy with a home urine pregnancy kit a few months ago but has not yet followed up with a physician. She takes no medications. Vital signs are within normal limits. Pelvic examination shows a uterus consistent in size with a 36-week gestation. Laboratory studies show: Hemoglobin 10.6 g/dL Serum Glucose 88 mg/dL Hepatitis B surface antigen negative Hepatitis C antibody negative HIV antibody positive HIV load 11,000 copies/mL (N < 1000 copies/mL) Ultrasonography shows an intrauterine fetus consistent in size with a 36-week gestation. Which of the following is the most appropriate next step in management of this patient?

Start cART and schedule cesarean delivery at 38 weeks' gestation

Intrapartum zidovudine and vaginal delivery when labor occurs

Intrapartum zidovudine and cesarean delivery at 38 weeks' gestation

Start cART and prepare for vaginal delivery at 38 weeks' gestation

Conduct cesarean delivery immediately

A 29-year-old woman tests positive for HIV during pregnancy screening. She is concerned about transmission to her baby. Which of the following interventions most significantly reduces the risk of vertical transmission?

Antiretroviral therapy during pregnancy and labor

A 2900-g (6.4-lb) male newborn is delivered at term to a 29-year-old primigravid woman. His mother had no routine prenatal care. She reports that the pregnancy was uncomplicated apart from a 2-week episode of a low-grade fever and swollen lymph nodes during her early pregnancy. She has avoided all routine vaccinations because she believes that “natural immunity is better.” The newborn is at the 35th percentile for height, 15th percentile for weight, and 3rd percentile for head circumference. Fundoscopic examination shows inflammation of the choroid and the retina in both eyes. A CT scan of the head shows diffuse intracranial calcifications and mild ventriculomegaly. Prenatal avoidance of which of the following would have most likely prevented this newborn's condition?

Exposure to unvaccinated children

HIV in pregnancy and vertical transmission for USMLE Step 2 CK: High-Yield Microbiology Lessons

Screening & Risks - The First Look

Universal Screening: Opt-out HIV screening for all pregnant women at the first prenatal visit.
- Test: 4th-gen antigen/antibody (p24 Ag & HIV-1/2 IgG) assay.
- Repeat testing in the 3rd trimester (<36 weeks) for high-risk women or those in high-prevalence areas.
Major Risk Factors for Vertical Transmission:
- High maternal viral load (>1,000 copies/mL) - the most critical factor.
- Vaginal delivery with high viral load.
- Prolonged rupture of membranes (>4 hours).
- Co-infections like STIs.

⭐ The single most important predictor of mother-to-child transmission (MTCT) is the maternal plasma HIV RNA level near delivery.

Maternal Care - Suppress to Save

Universal Screening: All pregnant women should be screened for HIV at the first prenatal visit.
Immediate cART: Initiate combination antiretroviral therapy (cART) for all HIV-positive pregnant women immediately, regardless of CD4 count or viral load, to achieve an undetectable viral load.
- Continue effective pre-existing regimens.
- Avoid dolutegravir in the first trimester due to a small risk of neural tube defects.
Delivery Mode Decision: Based on maternal viral load (VL) at ~36 weeks.

Infant Prophylaxis: Post-exposure prophylaxis with Zidovudine (AZT) for 4-6 weeks.
⚠️ Breastfeeding is contraindicated in the USA and other resource-rich settings.

⭐ The single most important factor determining the risk of vertical transmission is the maternal plasma viral load at delivery.

Neonate & Postpartum - Baby's Shield

Immediate Neonatal Care: All infants born to HIV+ mothers should receive postpartum antiretroviral (ARV) prophylaxis, ideally within 6-12 hours of birth, to minimize transmission risk.
ARV Regimen & Duration:
- Low-risk infants (maternal viral load <50 copies/mL): Zidovudine (ZDV) monotherapy for 4 weeks.
- High-risk infants (maternal viral load ≥50 copies/mL or unknown): Combination ART.
Feeding: Formula feeding is recommended; breastfeeding is contraindicated in the U.S.
PJP Prophylaxis: Start Trimethoprim-sulfamethoxazole (TMP-SMX) at age 4-6 weeks.

⭐ With optimal maternal and infant ARV management, the risk of perinatal HIV transmission is reduced to <1%.

Mother and baby protected from viruses by a shield

High‑Yield Points - ⚡ Biggest Takeaways

Vertical transmission of HIV occurs most commonly during the peripartum period.

The most significant risk factor for transmission is a high maternal viral load.

Initiate combination antiretroviral therapy (cART) for all pregnant individuals, regardless of CD4 count.

Cesarean delivery is recommended for viral loads >1,000 copies/mL.

Diagnose infants with HIV DNA or RNA PCR, not antibody tests.

Infants receive zidovudine prophylaxis after birth.

Breastfeeding is contraindicated in resource-rich settings.

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