To investigate risk factors for mother-to-child transmission of HIV-1, particularly sexual behavior before and during pregnancy.Design and methods:
This study is part of a prospective cohort study in Butare, Rwanda, of 318 HIV-1-seropositive and 309 HIV-1-seronegative women enrolled during pregnancy and followed for a mean duration of 21 months (range, 8–34 months). Clinical follow-up of the mother–infant pairs was performed at 6-week intervals during the first year of life and at 4-month intervals thereafter. Detailed sexual history interviews were conducted during pregnancy and at the first postnatal visit.Results:
Of 184 singleton infants born to HIV-1-infected mothers who survived the neonatal period, 32 (17%) children were classified as HIV-1-infected, 130 (71%) as not infected, and 22 (12%) died with indeterminate HIV-1 infection status. The vertical transmission rate was estimated to be between 20 and 29%. Unprotected sexual intercourse with increased number of partners during the past 5 years was strongly associated with mother-to-child transmission (P<0.001), even after adjustment for maternal CD4/CD8 ratio, parity, history of sexually transmitted diseases, and evidence of genital infection during pregnancy. In a multivariate analysis, excluding children with indeterminate HIV-1 status, odds ratios for vertical transmission were 2.6 [95% confidence interval (CI), 1.0–6.9] for maternal CD4/CD8 ratio <0.5 and 3.6 (95% CI, 1.1–11.8) for more than three sexual partners versus a single partner. Women with more than one sexual partner during the first trimester of pregnancy were at particularly high risk of transmitting the virus.Conclusion:
Unprotected sexual intercourse with multiple partners before and during pregnancy in a population with high HIV-1 seroprevalence may well increase the likelihood of HIV-1 transmission from an infected mother to her child.