In utero and intra-partum HIV-1 transmission and acute HIV-1 infection during pregnancy: Using the BED capture enzyme-immunoassay as a surrogate marker for acute infection

Objective: The BED assay was developed to estimate the proportion of recent HIV infections in a population. We used the BED assay as a proxy for acute infection to quantify the associated risk of mother-tochild-transmission (MTCT) during pregnancy and delivery. Design A total of 3773 HIV-1 sero-positive women were tested within 96 h of delivery using the BED assay, and CD4 cell count measurements were taken. Mothers were classified according to their likelihood of having recently seroconverted. Methods: The risk of MTCT in utero and intra-partum was assessed comparing different groups defined by BED and CD4 cell count, adjusting for background factors using multinomial logistic models. Results: Compared with women with BED≥0.8/CD4≥350 (typical of HIV-1 chronic patients) there was insufficient evidence to conclude that women presenting with BED<0.8/CD4≥350 (typical of recent infections) were more likely to transmit in utero [adjusted odds ratio (aOR)=1.37, 96% confidence interval (CI) 0.90-2.08, P=0.14], whereas women with BED<0.8/CD4 200-349 (possibly recently infected patients) had a 2.57 (95% CI 1.39-4.77, P-value<0.01) odds of transmitting in utero. Women who had BED<0.8/CD4<200 were most likely to transmit in utero (aOR 3.73, 95% CI 1.27- 10.96, P=0.02). BED and CD4 cell count were not predictive of intra-partum infections. Conclusions: These data provide evidence that in utero transmission of HIV might be higher among women who seroconvert during pregnancy. Published by Oxford University Press on behalf of the International Epidemiological Association