Background:  Without intervention, the risk of mother-to-child transmission (MTCT) of HIV ranges between 25% and 40% in breastfeeding populations. Each year more than 2 million infants are born to HIV-infected women, primarily in Sub-Saharan Africa. Without treatment, 50% of perinatally infected infants will die before age 2. In developed nations, remarkable progress has been made toward maximally reducing MTCT. However, in resource-poor settings where >95% of all cases of MTCT occur, only about 10% of pregnant HIV-infected women are currently benefiting from any PMTCT services. A truly population-based roll-out of PMTCT has been prevented by multiple barriers:  limited access to HIV counseling and testing, poor geographic coverage in rural areas, a crumbling maternal and child health-care infrastructure, unavailability of quality maternity and antenatal care, regular stock-outs of test kits and other supplies, infrequent male partner involvement, an increasingly severe human resource crisis, and limited supervisory support capacity. Widespread implementation of routine “opt-out” rapid HIV testing and counseling in antenatal and maternity settings, short-course peripartum antiretroviral prophylaxis, and ART for eligible mothers could reduce MTCT in resource-poor settings by greater than 75%. Between 20% and 40% of HIV-infected pregnant women are eligible for ART, depending on the CD4 cut-off used; however, only about 1% currently receive ART.  Early clinical staging and prompt CD4 testing of HIV-infected pregnant women are indicated. Moreover, because safe and acceptable alternatives to breastfeeding are not currently a viable option for most HIV-infected women, it is critical to identify interventions to maximally reduce postnatal HIV transmission through breast milk. Novel trials are investigating potential vaccine strategies and antiretrovirals for the mother and/or infant to prevent breastfeeding transmission. 

Conclusions:  To reduce global MTCT of HIV by 50% by the year 2010, a radical increase in access to HIV testing and counseling and in PMTCT coverage is necessary in resource-poor settings. Rapid scale-up of PMTCT services and provision of comprehensive, family-centered HIV care and treatment for women, children and their families are global priorities. The public health response must include effective linkages between PMTCT, ART, and family planning services. Ultimately, primary HIV prevention in young women and men holds the key to PMTCT.