MOTHER-TO-CHILD TRANSMISSION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) AND ITS DETERMINANTS - A COHORT STUDY IN KIGALI, RWANDA

The authors report the results of the first 2 years of follow-up of a prospective cohort study on the mother-to-child transmission of human immunodeficiency virus type 1 (HIV-1) and its determinants which start ed in November 1988 in Kigali, Rwanda. The study sample consists of 21 8 newborns of 215 HIV-1 seropositive women matched to 218 newborns of 216 HIV-1 seronegative women of the same age and parity. They were fol lowed every 2 weeks during the first 2 years of follow-up. HIV-1 antib odies were detected by enzyme-linked immunoadsorbent assay and Western blot at 3-month intervals. Two methods of calculating the mother-to-c hild transmission rate were used: method 1 combines the information pr ovided by the persistence of HIV-1 antibodies at 15 months of age in c hildren born to HIV seropositive mothers and the excess mortality in t his group compared with the cohort of children born to HIV seronegativ e mothers; method 2 is a case-by-case evaluation of all the children b orn to HIV seropositive mothers. A logistic regression model was used to study the determinants of transmission. The probability of survival at 24 months of age was 81% (95% confidence interval (CI) 75-86) in c hildren born to seropositive mothers, compared with 95% (95% Cl 92-98) in children born to seronegative mothers (p < 0.001). The mother-to-c hild transmission rate calculated with method 1 was 25.7% (95% Cl 18.8 -32.5). With method 2, the medium estimate was 24.7%. In the multivari ate analysis, a CD4/CD8 ratio <0.5 was the only maternal factor statis tically associated with an increased risk of mother-to-child transmiss ion of HIV-1 (odds ratio = 2.9, 95% Cl 1.2-7.2). The authors findings present evidence for a higher mother-to-child transmission rate of HIV -1 in children born in Rwanda than in industrialized countries.