Objective: To evaluate whether there is increased mother-to-child transmission of human immunodeficiency virus (HIV)-1 associated with deliveries at 40 weeks of estimated gestational age (EGA) or greater in pregnant women with HIV-1 viral loads of 1,000 copies/mL or less.
Methods: We performed a secondary analysis of the Eunice Kennedy Shriver National Institute of Child Health and Human Development International Site Development Initiative Perinatal and Longitudinal Study in Latin American Countries and International Maternal Pediatric Adolescent AIDS Clinical Trials P1025 cohorts. We included pregnant women with HIV-1 with recent viral loads of 1,000 copies/mL or less at the time of delivery and compared delivery outcomes at between 38 and less than 40 weeks EGA with delivery outcomes at 40 weeks EGA or greater, the exposure of interest. Our primary outcome of interest was mother-to-child transmission, and secondary outcomes included indicators of maternal and neonatal morbidity. We examined the association between EGA and mother-to-child transmission using Poisson distribution. Associations between EGA and secondary outcomes were examined through bivariate analyses using Pearson χ and Fisher exact test or the nonparametric Mann-Whitney U test.
Results: Among the 2,250 eligible neonates, eight neonates were infected with HIV-1 (overall transmission rate 0.4%, 95% CI 0.2-8.1%, 40 weeks EGA or greater 0.5% [3/621, 95% CI 0.2-1.4%], less than 40 weeks EGA 0.3% [5/1,629, 95% CI 0.1-0.7%]); there was no significant difference in transmission by EGA (rate ratio 1.57, 95% CI 0.24-8.09, P=.77). There was no difference in maternal viral load between the two groups nor was there a difference in timing of transmission among neonates born with HIV-1.
Conclusion: In pregnant women with well-controlled HIV-1, the risk of mother-to-child transmission did not differ significantly by EGA at delivery, although we were not powered to demonstrate equivalence of proportions of mother-to-child transmission between EGA groups.