Background:  Major progress has been made in prevention of mother-to-child transmission (MTCT) of HIV-1 and in the medical management of HIV-1-infected women. The NISDI Perinatal Study is a prospective cohort study of HIV-1-infected women and their infants in Argentina, the Bahamas, Brazil, and Mexico. The primary objectives of the study are to describe HIV-1-infected pregnant women and their infants at participating sites, and to characterize adverse events during pregnancy and the postpartum period/early infancy.   

Methods:  Enrollment into the study began in September 2002. Pregnant women receiving antenatal care at participating clinical sites were eligible for enrollment prior to delivery if there was documentation of pregnancy and of HIV-1 infection, if the subject intended to deliver at a participating clinical site and to be followed for 6 months (along with her infant) after delivery, and if the subject was willing and able to provide informed consent. Study visits occurred during pregnancy, at labor and delivery, and hospital discharge, and through 6 months postpartum. Infants were evaluated at birth and at hospital discharge, and through 6 months of age. A medical history and physical examination were performed, and laboratory evaluations were obtained, at study visits for women and their infants. 

Results:  Between September 2002 and June 2004, 711 women were enrolled in the cohort (at median gestational age of 27 weeks), with retention of 99% of these women and their infants through June 2004. At enrollment:  plasma HIV-1 RNA below detection limit, 37%; detection limit to 10,000 copies/mL, 20%; > 10,000 copies/mL, 43%]; CDC clinical classification (A, 85%; B, 7%; C, 8%); CDC immunologic category (1, 17%; 2, 56%; 3, 27%). Most complex regimen of ART received during pregnancy:  0, 4%; 1, 6%; 2, 7%; 3, 76% (most commonly zidovudine [ZDV]/lamivudine [3TC]/nevirapine [NVP] (n = 244) or ZDV/3TC/nelfinavir [NFV] (n = 266)]; 4+, 6%. Mode of delivery:  vaginal, 42%; caesarean section before labor and ruptured membranes (ECS), 40%; other caesarean section, 18%. By June 2004, 587 live births had occurred and of these, 586 (99.8%) did not breastfeed. Four infants (0.7%; 95% CI 0.2 to 1.7) have become HIV-1-infected. 

Conclusions:  A very low rate of MTCT of HIV-1 has been achieved among this population of HIV-1-infected women in Latin America and the Caribbean with utilization of the prophylactic interventions known to be efficacious (ART, ECS, and complete avoidance of breastfeeding).   

Keywords: mother-to-child transmission; HIV-infected women; prospective cohort study