We describe the impact of strategies to reduce HIV-1 vertical transmission on a cohort of pregnant women and evaluate toxicity related to antiretroviral (ARV) therapy and prevalence of birth defects. In this observational, retrospective, longitudinal and descriptive study, we have reviewed the data base and clinical charts from a cohort of 351 pregnant women with HIV infection admitted to a public hospital in Buenos Aires from April 1994 to August 2003. Eighty percent of women were infected by sexual transmission. Diagnosis of HIV infection was performed before pregnancy in 38.5% of cases; 241 patients received some kind of ARV therapy, combined therapy was administered in 123 of cases. The overall transmission rate was 9.6%, and antiretroviral therapy was the most significant factor associated with the transmission rate. HIV transmission odds were 0.04 for any ARV treatment versus no therapy. No cases of HIV transmission were observed among women given combination ARV therapy. More prevalent secondary effects associated to ARV therapy were anemia, hypercholesterolemia, increase of ALP and hypertrigliceridemia. In conclusion, antiretroviral therapy, particularly combined ARV therapy, irrespective of type of delivery, was associated with a reduced risk of HIV transmission without an increase in toxicity or incidence of congenital abnormalities in the short-term.