HIV acquisition in pregnancy: implications for mother-to-child transmission at the population level in sub-Saharan Africa.

Estimates of population-level HIV acquisition risk in sub-Saharan Africa should not be taken directly from per-condomless-coital-act studies to estimate vertical transmission. Changes in sexual behaviour and differences in HIV-serodiscordancy during pregnancy/postpartum reduce the impact of increased risk of HIV acquisition per-condomless-coital-act, this will vary by region.