To determine the incidence rate of, and the relative time to pregnancy by HIV status in US women between 2002 and 2009. The Women's Interagency HIV Study (WIHS) is an ongoing, multicenter prospective cohort study of the natural and treated history of HIV infection and related outcomes among women with and without HIV. Eligible participants were 45 years of age or less; sexually active with male partner(s) or reported a pregnancy outcome within the past year; and never reported hysterectomy, tubal ligation, or oopherectomy. Poisson regression was conducted to compare pregnancy incidence rates over time by HIV status. Relative time to pregnancy was ascertained via Kaplan-Meier plots and generalized gamma survival analysis. Adjusting for age, number of male sex partners, contraception, parity, exchanging sex, and alcohol use, HIV infection was associated with a 40% reduction in the incidence rate of pregnancy [incidence rate ratio = 0.60, 95% confidence interval (CI) 0.46-0.78]. The time for HIV-infected women to become pregnant was 73% longer relative to HIV-uninfected women (relative time = 1.73, 95% CI 1.35-2.36). In addition to HIV infection, decreased parity and older age were independent predictors of lower pregnancy incidence. Despite the beneficial effects of modern antiretroviral therapy on survival and prevention of maternal-to-child transmission, our findings suggest that pregnancy incidence remains lower among HIV-infected women. Whether this lower incidence is due to behavioral differences or reduced biologic fertility remains an area worthy of further study.
