Pregnant women who use protease inhibitors (PIs) during their first trimester have a more than 50 percent increased risk of premature delivery, according to a recent paper from the Pediatric HIV/AIDS Cohort Study. Regimens with non-nucleoside reverse-transcriptase inhibitors or triple-nucleosides were not associated with preterm delivery in the study, nor was PI use in the second or third trimesters. Previous research on how PIs affect preterm birth has been mixed, with some agreeing with these latest conclusions but others finding no association.

“I think we need more data before we would recommend against use” of PIs to pregnant women, says the study's principal investigator, Heather Watts, MD, a medical officer at the Eunice Kennedy Shriver National Institute of Child Health & Human Development in Rockville, Maryland.