A common medication used to help prevent HIV transmission between a mother and her unborn child may have serious effects on fetal development. According to a report from UPI, a team of researchers from Harvard University has found that the drug, called atazanavir, taken by pregnant women who are HIV-positive, could alter the way their child develops regardless of whether or not the disease is actually transmitted.

The drug is used in conjunction with a series of other anti-retroviral drugs that are used both for the treatment of HIV-positive individuals and to help prevent the spread of the virus. Previous studies have suggested that the medication could cause developmental effects when taken by pregnant women, but researchers stopped short of telling people to discontinue its use.

The new study was published in the journal AIDS, and examined 167 women who had taken atazanavir during pregnancy, and additional 750 who did not. Researchers compared the effects of the medication along developmental baselines after a child had been growing for a year.

Children whose mothers took atazanavir as a part of an anti-retroviral treatment scored lower on language and social-emotional development tests. Children of mothers who had taken the drug scored lower on language development tests regardless of which trimester the medication was taken, but social-emotional development scores were only affected in children whose mothers took the drug during the second and third trimesters of pregnancy.

And that’s not all – children whose mothers had taken atazanavir also fell behind other children in motor and adaptive behavioral development. While the study’s sample size was too small to determine a serious correlation, the results certainly call for further investigation into the possibility of serious developmental effects as a result of atazanavir treatment.

A press release describing the details of the study can be found here.