OBJECTIVE: To examine the association between maternal HIV infection and pregnancy outcomes controlling for potential confounding factors among a cohort of HIV-uninfected and HIV-infected pregnant women in Dar es Salaam, Tanzania. DESIGN: Prospective cohort study. METHODS: A cohort of 1,078 HIV-infected and 502 HIV-uninfected pregnant women between 12 and 27 weeks of gestation were enrolled and followed up until delivery. Multiple regression models were used to compare the risk of adverse pregnancy outcomes among HIV-uninfected women with those among HIV-infected women overall, and separately among asymptomatic or symptomatic HIV-infected women. RESULTS: No significant differences between HIV-uninfected women and HIV-infected women were observed in risks of fetal loss or low birthweight or in the weight, head circumference and gestational age of infants at birth. HIV-infected women were more likely to have severe immature infants (<34 weeks) than HIV-uninfected women (multivariate RR 1.54 [95% CI 0.90-2.48]; P= 0.05). There was a significantly higher risk of low birthweight (RR 2.29, 95% CI 1.34-3.92; P = 0.03) and prematurity (<37 weeks) (RR 1.93, 95% CI 1.35-2.77; P = 0.0003) among symptomatic HIV-infected women when compared with HIV-uninfected women. CONCLUSION: HIV-infected women, particularly those whoare symptomatic, are at a higher risk of adverse pregnancy outcomes.