Objectives: To determine the impact of time between initiating highly active antiretroviral therapy (HAART) and delivery—duration of antenatal HAART—on perinatal HIV infection.
Design: We conducted a retrospective cohort analysis of pregnant HIV-infected women in Lusaka, Zambia. Women in our cohort were receiving HAART and had an infant HIV polymerase chain reaction test between 3 and 12 weeks of life.
Methods: We examined factors associated with infant HIV infection and performed a locally weighted regression analysis to examine the effect of duration of antenatal HAART on perinatal HIV infection.
Results: From January 2007 to March 2010, 1813 HIV-infected pregnant women met inclusion criteria. Mean gestational age at first antenatal visit was 21 weeks (SD ± 6), median CD4+ cell count was 231 cells per microliter (interquartile range: 164-329), and median duration of antenatal HAART was 13 weeks (interquartile range 8-19). Fifty-nine (3.3%) infants were HIV infected. Duration of antenatal HAART was the most important predictor of perinatal HIV transmission. Compared with women initiating HAART at least 13 weeks before delivery, women on HAART for ≤4 weeks had a 5.5-fold increased odds of HIV transmission (95% confidence interval: 2.6 to 11.7). Locally weighted regression analysis suggested limited additional prophylactic benefit beyond 13 weeks on antenatal HAART.
Conclusions: Low rates of mother-to-child HIV transmission can be achieved within programatic settings in Africa. Maximal effectiveness of prevention of mother-to-child transmission programs is achieved by initiating HAART at least 13 weeks before delivery.