MULTIPLE SEXUAL PARTNERS AND MOTHER-TO-CHILD TRANSMISSION OF HIV-1

Objective: To investigate risk factors for mother-to-child transmissio n of HIV-1, particularly sexual behavior before and during pregnancy. Design and methods: This study is part of a prospective cohort study i n Butare, Rwanda, of 318 HIV-1-seropositive and 309 HIV-1-seronegative women enrolled during pregnancy and followed for a mean duration of 2 1 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 intervie ws were conducted during pregnancy and at the first postnatal visit. R esults: Of 184 singleton infants born to HIV-1-infected mothers who su rvived the neonatal period, 32 (17%) children were classified as HIV-1 -infected, 130 (71%) as not infected, and 22 (12%) died with indetermi nate HIV-1 infection status. The vertical transmission rate was estima ted to be between 20 and 29%. Unprotected sexual intercourse with incr eased number of partners during the past 5 years was strongly associat ed with mother-to-child transmission (P<0.001), even after adjustment for maternal CD4/CD8 ratio, parity, history of sexually transmitted di seases, and evidence of genital infection during pregnancy. In a multi variate analysis, excluding children with indeterminate HIV-1 status, odds ratios for vertical transmission were 2.6 [95% confidence interva l (Cl), 1.0-6.9] for maternal CD4/CD8 ratio < 0.5 and 3.6 (95% Cl, 1. 1-11.8) for more than three sexual partners versus a single partner. W omen with more than one sexual partner during the first trimester of p regnancy were at particularly high risk of transmitting the virus. Con clusion: Unprotected sexual intercourse with multiple partners before and during pregnancy in a population with high HIV-1 seroprevalence ma y well increase the likelihood of HIV-1 transmission from an infected mother to her child.