Background:  Limited information exists from Africa regarding mother-to-child transmission (MTCT) among HIV-infected pregnant women initiated on HAART. In this study, predictors of MTCT were identified in South African women diagnosed with HIV during pregnancy and initiated on HAART for World Health Organization clinical stage 4 or CD4 count ≤250 cells/µL.

Methods:  A retrospective analysis was performed on a cohort of women followed in an Antenatal Antiretroviral Clinic (ANC ARV) at Johannesburg Hospital. Infant HIV infection was defined by a positive HIV-1 DNA polymerase chain reaction assay at 6 weeks of life. Univariate logistic regression was used to identify factors that predicted infant HIV infection. Analysis of variance was used to determine differences among mothers whose infants were HIV⁺, HIV^–, or status unknown due to loss to follow-up. For significant results, follow-up pairwise testing was performed.

Results:  A total of 689 women were referred to the ANC ARV between August 2004 and February 2007. The mean baseline CD4 count was 154 cells/µL. The most common HAART regimen was stavudine/lamivudine/nevirapine (82%). Of 302 mother-infant pairs who completed follow-up through 6 weeks post partum, 15 infants (5%) were diagnosed with HIV infection. Shorter duration of HAART during pregnancy and lower CD4 cell counts were associated with infant HIV positivity (p = 0.001 and p = 0.03, respectively, Table 1). Neither baseline nor follow-up HIV viral loads were significant predictors of transmission. This may be due to high variance in viral loads and small numbers of mothers with complete viral load data. Duration of HAART in pregnancy differed among mothers whose infants were HIV⁺, HIV^–, and HIV status unknown (F test, p = 0.0005, Table 2). Mothers of HIV-infected infants had shorter treatment times compared to those of uninfected infants (5.1 vs 11.2 weeks, p = 0.001). For each additional week of HAART, the odds of transmission were reduced by 27%. The transmission rate for women who received >7 weeks of HAART during gestation was 0.3%.

Conclusions:  Overall, women receiving HAART during pregnancy in South Africa have low rates of MTCT. Shorter duration of HAART during pregnancy was significantly associated with infant HIV infection. Strategies are needed to facilitate earlier treatment of HIV-infected pregnant women with advanced disease.