Glaxo and the FDA have issued new warnings on Paxil-related birth defects for women who take the drug in their first trimester of pregnancy.

“Healthcare professionals are advised to carefully weigh the potential risks and benefits of using Paxil in women during pregnancy and to discuss these findings as well as treatment alternatives with their patients,” FDA says.

A new study marked the progress of 3,500 women that were taking Paxil during their first trimester. The study revealed that among those women who were on antidepressants and whose babies were born with birth defects, the women that were taking Paxil had twice the amount of defects in their children as the women taking other pills.

While birth defects aren’t common in the U.S., it still isn’t clear whether Paxil is directly responsible for the defects in children, according to Glaxo. FDA officials have decided to have the labels on Paxil carry warnings to pregnant women.

Most of the birth defects that were detected during the study were heart-related. Of these, the most common heart defects were ventricular septal defects, or holes that are between the heart’s two main valves that are used to pump blood through the body. This was a retrospective epidemiological study in that the researchers looked at big groups of people in a hindsight kind of way. There is not information on the children that were born with defect to women that were not taking Paxil while they were pregnant.

So while Glaxo continues to claim that there is no direct evidence linking birth defects in newborns to women that were taking Paxil during their pregnancies, the company and the FDA still decided to issue new warnings on the potential risks of pregnant women taking the drug.