DETERMINANTS OF MOTHER-TO-CHILD TRANSMISSION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTION IN A COHORT FROM DURBAN, SOUTH-AFRICA

Objectives. To determine the vertical transmission rate of HIV-1 infec tion and to assess the influence of maternal risk factors on transmiss ion in infants born to HIV-1-infected black women in Durban. Design. A prospective, hospital-based cohort study conducted at King Edward VII I hospital, Durban. HIV-1-seropositive women were enrolled into the st udy, and their infants were followed up at regular intervals from birt h to early childhood, The infection status of the children was classif ied and the transmission rate was computed according to the recommenda tions of the workshop held in Ghent, Belgium (1992). Results. The fina l cohort of 181 infants were classified as 48 infected, 93 not infecte d and 40 indeterminate. Clearance of maternal antibodies was achieved by 12 months of age in virtually all infants who became seronegative. The intermediate transmission rate was 34% (95% confidence interval, 2 6 to 42), Deliveries by cesarean section had significantly lower trans mission (relative risk, 0.46; 95% confidence interval 0.23 to 0.91). W omen with lower hemoglobin concentrations during pregnancy (<10 g/dl) had an increased risk of transmission (relative risk, 1.99; 95% confid ence interval, 1.18 to 3.34), Advanced maternal age, multiparity, posi tive syphilis serology, duration of ruptured membranes, preterm delive ry and breast-feeding were not associated with an increased risk of tr ansmission. Conclusions. This study, the first from South Africa, has confirmed that the rate of vertical transmission of HIV-1 is as high a s that reported from most African cohorts, Cesarean sections were prot ective against transmission, whereas low hemoglobin values were associ ated with an increased risk of transmission, Twelve months could be us ed as the cutoff age for the diagnosis of vertical infection using ant ibody tests.