Recommendations for the Use of Antiretroviral Drugs in Pregnant Women with HIV Infection and Interventions to Reduce Perinatal HIV Transmission in the United States

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Lessons From Clinical Trials of Antiretroviral Interventions to Reduce Perinatal Transmission of HIV

Mechanisms of Action of Antiretroviral Prophylaxis in Reducing Perinatal Transmission of HIV

Last Updated: July 31, 2012; Last Reviewed: July 31, 2012

Panel's Recommendations Regarding Mechanisms of Action of Antiretroviral Prophylaxis in Reducing Perinatal Transmission of HIV

Panel's Recommendation

  • Antiretroviral (ARV) drugs reduce perinatal transmission by several mechanisms, including lowering maternal antepartum viral load and providing infant pre- and post-exposure prophylaxis. Therefore, combined antepartum, intrapartum, and infant ARV prophylaxis is recommended to prevent perinatal transmission of HIV (AI).
Rating of Recommendations: A = Strong; B = Moderate; C = Optional
Rating of Evidence: I = One or more randomized trials with clinical outcomes and/or validated laboratory endpoints; II = One or more well-designed, nonrandomized trials or observational cohort studies with long-term clinical outcomes; III = Expert opinion

Antiretroviral (ARV) drugs can reduce perinatal transmission through a number of mechanisms. Antenatal drug administration decreases maternal viral load in blood and genital secretions, which is a particularly important mechanism of action in women with high viral loads. Even among women with HIV RNA levels <1,000 copies/mL, however, ARV drugs have been shown to reduce risk of transmission.1 In addition, the level of HIV RNA at delivery and receipt of antenatal ARV drugs are independently associated with risk of transmission, suggesting that reduction in viral load is not solely responsible for the efficacy of ARV prophylaxis.2,3

Another mechanism of protection is infant pre-exposure prophylaxis achieved by administering ARV drugs that cross the placenta from mothers to infants and produce adequate systemic drug levels in the infants. This mechanism of protection likely is particularly important during passage through the birth canal, a time when infants receive intensive exposure to maternal genital-tract virus. Infant post-exposure prophylaxis is achieved by administering drugs to infants after birth. This intervention provides protection from cell-free or cell-associated virus that may have entered the fetal/infant systemic circulation through maternal-fetal transfusion associated with uterine contractions during labor or systemic dissemination of virus swallowed during infant passage through the birth canal.

The efficacy of ARV drugs in reducing perinatal transmission likely is multifactorial, and each of the mechanisms previously described may make a contribution. The importance of the pre- and post-exposure components of prophylaxis in reducing perinatal transmission is demonstrated by the efficacy of interventions that involve administration of ARVs only during labor and/or to the newborns, discussed in the next section.4-10


  1. Ioannidis JP, Abrams EJ, Ammann A, et al. Perinatal transmission of human immunodeficiency virus type 1 by pregnant women with RNA virus loads <1000 copies/ml. J Infect Dis. Feb 15 2001;183(4):539-545. Available at
  2. Cooper ER, Charurat M, Mofenson L, et al. Combination antiretroviral strategies for the treatment of pregnant HIV-1-infected women and prevention of perinatal HIV-1 transmission. J Acquir Immune Defic Syndr. Apr 15 2002;29(5):484-494. Available at
  3. Sperling RS, Shapiro DE, Coombs RW, et al. Maternal viral load, zidovudine treatment, and the risk of transmission of human immunodeficiency virus type 1 from mother to infant. Pediatric AIDS Clinical Trials Group Protocol 076 Study Group. N Engl J Med. Nov 28 1996;335(22):1621-1629. Available at
  4. Jackson JB, Musoke P, Fleming T, et al. Intrapartum and neonatal single-dose nevirapine compared with zidovudine for prevention of mother-to-child transmission of HIV-1 in Kampala, Uganda: 18-month follow-up of the HIVNET 012 randomised trial. Lancet. Sep 13 2003;362(9387):859-868. Available at
  5. Petra Study Team. Efficacy of three short-course regimens of zidovudine and lamivudine in preventing early and late transmission of HIV-1 from mother to child in Tanzania, South Africa, and Uganda (Petra study): a randomised, double-blind, placebo-controlled trial. Lancet. Apr 6 2002;359(9313):1178-1186. Available at
  6. Moodley D, Moodley J, Coovadia H, et al. A multicenter randomized controlled trial of nevirapine versus a combination of zidovudine and lamivudine to reduce intrapartum and early postpartum mother-to-child transmission of human immunodeficiency virus type 1. J Infect Dis. Mar 1 2003;187(5):725-735. Available at
  7. Taha TE, Kumwenda NI, Gibbons A, et al. Short postexposure prophylaxis in newborn babies to reduce mother-to-child transmission of HIV-1: NVAZ randomised clinical trial. Lancet. Oct 11 2003;362(9391):1171-1177. Available at
  8. Gaillard P, Fowler MG, Dabis F, et al. Use of antiretroviral drugs to prevent HIV-1 transmission through breast-feeding: from animal studies to randomized clinical trials. J Acquir Immune Defic Syndr. Feb 1 2004;35(2):178-187. Available at
  9. Gray GE, Urban M, Chersich MF, et al. A randomized trial of two postexposure prophylaxis regimens to reduce mother-to-child HIV-1 transmission in infants of untreated mothers. AIDS. Aug 12 2005;19(12):1289-1297. Available at
  10. Nielsen-Saines K, Watts DH, Veloso VG, et al. Three postpartum antiretroviral regimens to prevent intrapartum HIV infection. N Engl J Med. Jun 21 2012;366(25):2368-2379. Available at

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