BACKGROUND: This systematic review focuses on antiretroviral therapy (ART) for treating human immunodeficiency virus (HIV) infection in ART-eligible pregnant women. Mother-to-child transmission (MTCT) is the primary means by which children worldwide acquire HIV infection. MTCT occurs during three major timepoints during pregnancy and the postpartum period: in utero, intrapartum, and during breastfeeding. Strategies to reduce MTCT focus on these periods of exposure and include maternal and infant use of ART, caesarean section before onset of labour or rupture of membranes, and complete avoidance of breastfeeding. Where these combined interventions are available, the risk of MTCT is as low as 1-2%. Thus, ART used among mothers who require treatment of HIV for their own health also plays a significant role in decreasing MTCT.This review is one in a series of systematic reviews performed in preparation for the revision of the 2006 World Health Organization (WHO) Guidelines regarding "Antiretroviral Drugs for Treating Pregnant Women and Preventing HIV Infection in Infants" and "Antiretroviral therapy (ART) for HIV Infections in Adults and Adolescents." The findings from these reviews were discussed with experts, key stakeholders, and country representatives at the 2009 WHO guideline review meeting. The resulting WHO 2009 "rapid advice" preliminary guidance on adult and adolescent ART now recommends lifelong treatment for all adults with HIV infection and CD4 counts <350 cells/mm(3). These recommendations also apply to pregnant women who are HIV-infected and they place a high value on early ART to benefit the mother's own health (WHO 2009). The "rapid advice" preliminary guidance also aims to minimize side effects for mothers and their infants (WHO 2009). OBJECTIVES: Our objective was to assess the current literature regarding the treatment of HIV infection in pregnant women who are clinically or immunologically eligible for ART. This review includes an evaluation of the optimal time to start therapy in relation to the woman's laboratory parameters and/or gestational age. It also includes an analysis of which specific antiretroviral medications to start in women who are not yet on ART and which agents to continue in women who are already on ART. SEARCH STRATEGY: In June 2009, electronic searches were undertaken in these databases: Cochrane's "CENTRAL," EMBASE, PubMed, LILACS, and Web of Science/Web of Social Science. Hand searches were performed of the reference lists of all pertinent reviews and studies identified. Abstracts from relevant conferences were searched. Experts in the field were contacted to locate additional studies. The search strategy was iterative. SELECTION CRITERIA: We selected randomized controlled trials and observational studies that evaluated pregnant women with HIV infection who were eligible for ART according to criteria defined by the WHO guideline review committee. Studies were included in the systematic review when a comparison group was clearly defined and where the intervention comprised triple ART. For a study to be considered, each medication in the ART regimen needed to be clearly described. DATA COLLECTION AND ANALYSIS: Two authors independently assessed the selected studies for relevance and inclusion. Relevant data was then extracted from included studies, and the risk of bias assessed. In each included study, the relative risk (RR) for the intervention versus the comparison group was calculated for each outcome, as appropriate, with 95% confidence intervals (CIs). MAIN RESULTS: To our knowledge, there are no randomized controlled trials or observational studies that address the optimal time to start antiretroviral drugs in ART-eligible pregnant women in relation to the woman's laboratory parameters and/or gestational age. The medications to continue in ART-eligible pregnant women who are already receiving ART also have not been evaluated systematically in the current literature. The long-term mortality of HIV-positive pregnant women on ART for their own health, and the long-term virologic or clinical efficacy of ART in treating them, has not been evaluated in randomized clinical trials. In this review, surrogate outcomes for long-term mortality and virologic and clinical efficacy (e.g. MTCT and infant HIV transmission or death) were evaluated to determine the efficacy of specific antiretroviral regimens to start in women who are not yet on ART.Three randomized controlled trials and six observational studies were selected. No studies addressed comparative maternal mortality, which regimens to continue in women already on ART, or the laboratory parameters and gestational age at which to start therapy. The use of zidovudine (AZT), lamivudine (3TC) and lopinavir/ritonavir (LPV-r) starting at 28-36 weeks gestation in a breastfeeding population reduced infant HIV-transmission or death at 12 months compared to a short-course regimen (RR 0.64, 95% CI: 0.44-0.92) (deVincenzi, 2009). Starting AZT, 3TC, and nevirapine (NVP) at 34 weeks in a mixed-feeding population reduced infant HIV-transmission or death at 7 months compared to a short-course regimen (RR 0.39, 95% CI: 0.12-0.85) (Bae, 2008).In the Mma Bana study (a randomized controlled trial in a breastfeeding population) there was no difference in MTCT at six months between the AZT/3TC/LPV-r and AZT, 3TC, and abacavir (ABC) arms (RR 0.17, 95% CI: 0.02-1.44) (Shapiro, 2009). Both regimens also showed 92-95% efficacy in virologic suppression at delivery and during the breastfeeding period. In the Kesho Bora study there was a significant difference in MTCT at 12 months between breastfeeding women who initiated AZT/3TC/LPV-r starting between 28 and 36 weeks and those receiving a short course regimen (RR 0.58, 95% CI: 0.34-0.97) (deVincenzi, 2009). MTCT also decreased significantly when AZT/3TC/NVP was compared with a short-course regimen at seven months in a feeding intervention study (RR 0.15, 95% CI: 0.04-0.62) (Bae, 2008) and 12 months in a population where either exclusive breastfeeding or replacement feeding was encouraged (RR 0.14, CI: 0.04-0.47) (Ekouevi, 2008).In the Mma Bana study, there was increased risk of prematurity among infants born to women receiving AZT/3TC/LPV-r (RR 1.52, CI: 1.07- 2.17) compared with AZT/3TC/ABC (Shapiro, 2009). Ekouevi 2008 showed higher rates of infant low birth weight on AZT/3TC/NVP started at 24 weeks compared to a short course regimen started between 32 and 36 weeks (RR 1.81, 95% CI: 1.09- 3.0). Tonwe-Gold 2007 showed an increase in maternal severe adverse events among the women receiving AZT/3TC/NVP compared with a short-course regimen (RR 25.33, CI 1.49- 340.51). AUTHORS' CONCLUSIONS: In ART-eligible pregnant women with HIV infection, ART is a safe and effective means of providing maternal virologic suppression, decreasing infant mortality, and reducing MTCT. Specifically, AZT/3TC/NVP, AZT/3TC/LPV-r, and AZT/3TC/ABC have been shown to decrease MTCT. More research is needed regarding the use of specific regimens and their maternal and infant side-effect profiles.