Background: To investigate potential risk factors for perinatal (intrauterine and intrapartum) mother-to-child transmission (MTCT) of HIV in women unexposed to antiretroviral therapy (ART) during pregnancy.
Methods: We compared factors according to perinatal MTCT outcome among 2275 ART-naive (until the onset of labor) HIV-infected women in the Breastfeeding, Antiretrovirals and Nutrition study (2004-2010) in Lilongwe, Malawi. Factors included HIV viral load during pregnancy, food security, demographic characteristics, hematologic and blood chemistry measures, medical history and physical factors. Associations with perinatal MTCT and interactions with maternal viral load were assessed using simple and multivariable logistic regression.
Results: There were 119 (115 intrauterine and 4 intrapartum) cases of perinatal MTCT, only one to a mother with <1000 HIV copies/mL. Maternal viral loads >10,000 copies/mL were common (63.1%). Lower maternal viral load (<1000 copies/mL and 1000.1-10,000 copies/mL) was associated with reduced odds of perinatal MTCT [adjusted odds ratio (aOR), 0.1; 95% confidence interval (CI): 0.01-0.4 and aOR, 0.2; 95% CI: 0.1-0.4, respectively), compared with maternal viral load >10,000 copies/mL. Low CD4+ T cell count (≤350 cells/μL) was only associated with perinatal MTCT in unadjusted models. Food shortage (aOR, 1.8; 95% CI: 1.2-2.6), sexually transmitted infection (STI) (past year; aOR, 1.9; 95% CI: 1.0-3.7), histories of herpes zoster (aOR, 3.0; 95% CI: 1.6-5.6) and tuberculosis (aOR, 2.5; 95% CI: 1.1-5.7) were associated with increased odds of perinatal MTCT.
Conclusions: These findings confirm that lowering maternal HIV viral load is most important in preventing perinatal MTCT and support efforts to address food shortage, STI and tuberculosis prevention, while informing programs to improve ART coverage in pregnancy.