Prophylaxis for Maternal-to-Child HIV Transmission
The recommended drug for prevention of maternal-to-child HIV transmission is zidovudine (AZT), which should be administered as a three-part regimen: to the mother starting at 28 weeks gestation (or as soon as possible), intravenously during labor, and to the infant for 6 weeks after birth. 1
Core Recommendations Based on Clinical Scenarios
For HIV-Infected Pregnant Women Not on Treatment
Optimal regimen:
- Mother: Zidovudine 300 mg twice daily starting at 28 weeks gestation
- Intrapartum: Zidovudine 600 mg at labor onset, then 300 mg every 3 hours until delivery
- Infant: Zidovudine 4 mg/kg twice daily for 6 weeks 2
This approach reduces transmission by approximately 70% (from 25.5% to 8.3%) 2. The evidence supporting this comes from the landmark PACTG 076 trial, which established zidovudine as the foundation of perinatal HIV prevention 2.
For Women Requiring Treatment for Their Own Health
Highly active antiretroviral therapy (HAART) is recommended, ideally containing zidovudine as a component. The regimen should include:
- Zidovudine 300 mg twice daily
- Lamivudine 150 mg twice daily
- Plus a third agent (typically an integrase inhibitor or protease inhibitor)
Continue this regimen throughout pregnancy, with intravenous zidovudine during labor, and give the infant zidovudine for 6 weeks 3.
For Women Presenting in Labor Without Prior Treatment
Several effective options exist 1:
Single-dose nevirapine regimen:
- Mother: Nevirapine 200 mg orally at labor onset
- Infant: Nevirapine 2 mg/kg immediately after birth (within 48-72 hours)
- This reduces transmission by 47% compared to short-course zidovudine 1
Zidovudine plus lamivudine:
- Mother: Both drugs during labor and every 12 hours until delivery
- Infant: Both drugs for 7 days postpartum
- Reduces transmission by 40% 1
Intravenous zidovudine during labor plus 6 weeks oral zidovudine for infant (reduces transmission by 62%) 1
Combination approach: Nevirapine plus zidovudine regimen (theoretical benefit but no proven additional efficacy) 1
Critical Caveats and Pitfalls
Nevirapine resistance warning: Single-dose nevirapine induces resistance mutations in 19% of treatment-naïve women 1. To mitigate this, add a 7-day "tail" of zidovudine plus lamivudine after delivery 2.
Hepatotoxicity risk: Nevirapine carries significant hepatic toxicity risk in women with CD4 counts >250 cells/mm³ 2. Use alternative regimens in this population.
First trimester considerations: If a woman on antiretroviral therapy becomes pregnant, continue all medications. If stopping is considered due to teratogenicity concerns, discontinue all drugs simultaneously to prevent resistance, then restart in the second trimester 1.
Timing matters: For infants born to untreated mothers, initiate zidovudine within 6-12 hours of birth for maximum benefit 1. Efficacy decreases significantly when started after 48 hours 1.
For Infants Born to Mothers Who Received No Treatment
Recommended approach:
- Zidovudine for 6 weeks, initiated as soon as possible after delivery (preferably within 6-12 hours)
- Consider adding single-dose nevirapine immediately after birth
- This combination (nevirapine plus 4 weeks of zidovudine) is more effective than nevirapine alone 2
Modern Context
While the guidelines cited are from 2002-2007, zidovudine remains the cornerstone of prevention 20 years later 3. More recent evidence from 2017 suggests that in resource-rich settings, combination therapy with tenofovir/emtricitabine plus a protease inhibitor is increasingly used, though this may increase early neonatal death and preterm delivery compared to zidovudine/lamivudine 4. The 2017 BMJ guideline makes a weak recommendation for zidovudine plus lamivudine over tenofovir-based regimens when combined with most antiretrovirals, and a strong recommendation when combined with lopinavir/ritonavir 4.
Bottom line: Zidovudine-based prophylaxis remains the gold standard, with the specific regimen tailored to when the woman presents for care and whether she requires treatment for her own health.