Vertical HIV transmission: risk grows with duration of membrane rupture.

Between 1982 and 1990 researchers pooled data from 15 prospective cohort studies conducted in Europe and North America. This was aimed to test the hypothesis that the longer an HIV-infected pregnant womans membranes have been ruptured the higher the risk of vertical transmission. The researchers used logistic regression to calculate odds ratios estimating the strength of the association between the length of time membranes ruptured and the infants HIV status controlling for the mothers CD4 percentage mode of delivery receipt of antiretroviral therapy and the infants birth weight. Overall the results show that each 1-hour increase in duration of ruptured membranes represented a 2% increase in the risk of transmission. As in the univariate analysis the mode of delivery was the only factor that did not contribute to the risk of vertical transmission. It is noted that the risk was significantly elevated for women with low CD4 percentages and those whose infants weighed < 2500 g at birth; it was reduced if the woman her infant or both received antiretroviral therapy. Finally for women with AIDS this probability was 8% if the duration of membrane rupture was 2 hours and it rose to 31% if the membranes were ruptured for 24 hours.