Women living in world regions where HIV infection is common are at high risk of acquiring HIV infection during pregnancy and the postpartum period, according to a study by US researchers published in this week's PLOS Medicine. Alison Drake and colleagues from the University of Washington in Seattle also found that mothers who acquire HIV during pregnancy or postpartum are more likely to pass the infection on to their offspring than mothers with chronic HIV infections.

The authors reached these conclusions by reviewing relevant published studies and then using a model to estimate the HIV incidence rate and the association between pregnancy and postpartum status, HIV incidence and the risk and rates of mother to child transmission (MTCT).

The authors found that the combined HIV incidence rate among pregnant/postpartum women was 3.8/100 person-years. Furthermore, the number of new infections per number of people at risk was significantly higher in African countries than in non-African countries at 3.6% and 0.3%, respectively. The authors also found that among African women, the risk of MTCT was 2.9-fold higher during the postpartum period among those who had recently acquired HIV than among those with chronic HIV infection, and 2.3-fold higher during the pregnancy/postpartum periods combined.

Although limited by differences in the quality of the studies included in this review, these findings have important implications: they suggest that women living in regions where HIV infection is common should be offered repeat HIV testing during pregnancy and in the postpartum period to detect incident HIV infections, and that preventing HIV transmission during pregnancy and the postpartum period should be prioritized, for example, by counseling women about the need to use condoms to prevent transmission during this period of their lives.

The authors say: "Detection and prevention of incident HIV in pregnancy/postpartum should be prioritized, and is critical to decrease [mother to child transmission]."