Baclground:  We wanted to estimate the incidence of HIV during pregnancy and lactation.

Methods:  We conducted a prospective study of HIV^– sexually active women comprised of 2404 pregnant women, 2845 breastfeeding women, and 25,687 intervals of observation in non-pregnant/non-lactating women. HIV incidence per 100 person-years, and incidence rate ratios (IRR) and 95% confidence intervals (95% CI) were estimated by Poisson multivariate regression, with the non-pregnant and non-lactating women as the referent group. Married women were linked to their husbands to assess male risk behaviors.

Results:  HIV incidence was 2.7/100 person-years during pregnancy, 1.4/100 person-years during breastfeeding and 1.1/100 person-years in the non-pregnant and non-lactating women. The adjusted IRR = 1.94, 95% CI 1.19 to 3.18 during pregnancy and 1.29 (95% CI 0.91 to 3.18) during breast feeding. In a sub-analysis of married women linked to their male partners, the IRR of HIV acquisition during pregnancy was 2.17 (95% CI 1.16 to 4.04) after adjustment for male and female sexual risk behaviors.

Conclusions:  Pregnancy represents a special period of increased risk of HIV acquisition, and there is an urgent need to promote HIV prevention during pregnancy.

Keywords: Pregnancy; HIV acquisition; HIV incidence