Risk factors for detectable HIV-1 RNA at delivery among women receiving highly active antiretroviral therapy in the women and infants transmission study

Background: Detectable HIV-1 RNA at delivery is the strongest predictor of mother-to-child transmission. The risk factors for detectable HIV, including type of regimen, are unknown. We evaluated factors, including highly active antiretroviral (HAART) regimen, associated with detectable HIV-1 RNA at delivery in the Women and Infants Transmission Study (WITS). Methods: Data from 630 HIV-1-infected women who enrolled from 1998 to 2005 and received HAART during pregnancy were analyzed. Multivariable analyses examined associations between regimens, demographic factors, and detectable HIV-1 RNA (>400 copies/milliliter) at delivery. Results: Overall, 32% of the women in the cohort had detectable HIV-1 RNA at delivery. Among the subset of 364 HAART-experienced women, a lower CD4⁺ cell count at enrollment [adjusted odds ratio (AOR) = 1.20 per 100 cells/μL, confidence interval (CI) 1.04 to 1.37] and higher HIV-1 RNA at enrollment (AOR = 1.52 per log10 copies/milliliter, CI 1.32 to 1.75) were significantly associated with detectable HIV-1 RNA levels at delivery. For the 266 HAART-naive women, both lower CD4 cell count at enrollment (AOR = 1.24 per 100 cells/μL, CI 1.05 to 1.48) and higher HIV-1 RNA at enrollment (AOR = 1.35 per log10 copies/milliliter, CI 1.12 to 1.63) were associated with detectable HIV-1 RNA at delivery. In addition, age at delivery (AOR = 0.92 per 10 years older, CI 0.86 to 0.99) and maternal illicit drug use (AOR = 3.15, CI 1.34 to 7.41) were significantly associated with detectable HIV-1 RNA at delivery among HAART-naive women. Type of HAART regimen was not significant in either group. Conclusions: Lack of viral suppression at delivery was common in the WITS cohort, but differences by antiretroviral regimen were not identified. Despite a transmission rate below 1% in the last 5 years of the WITS cohort, improved measures to maximize HIV-1 RNA suppression at term among high-risk women are warranted.