LILAC aimed to characterise HIV-infected pregnant women and their HIV-exposed children in Latin America. Between 2008 and 2009, the study recruited over 400 pregnant women from Argentina, Brazil and Peru who tested positive for Human Immunodeficiency Virus (HIV) and were at least 22 weeks pregnant at the time of enrollment. Participants were followed up twice during pregnancy, at delivery, at hospital discharge, at 6 to 12 weeks postpartum, at 6 months postpartum, and every 6 months thereafter until the study concluded in 2011. Data were also collected from over 300 child participants at birth, 6-12 weeks, and 6 months, and every 6 months thereafter until the study concluded. An additional 100 child participants, aged 6 months to 5 years, were recruited as part of a separate static cohort and followed twice a year until the study concluded in 2011.