The FDA warned doctors today that preliminary results implicate the antidepressant Paxil (paroxetine) with an increased risk of birth defects.

The FDA informed doctors that results of new studies suggest that Paxil use during the first trimester increases the risk of congenital heart defects in the developing fetus.

The FDA advised physicians to discuss the potential risk of birth defects with women taking Paxil who plan to become pregnant or who are in the first trimester of pregnancy. Doctors should consider discontinuing Paxil in these patients and switching to another antidepressant if indicated. In some patients, the benefits of continuing Paxil may be greater than the potential risk to the fetus, the FDA said.

In general, however, the FDA advised that the drug should not be taken during pregnancy. But women who are taking Paxil should consult their physicians before stopping the drug. The FDA action was prompted by results of two studies that showed that women who took Paxil during the first three months of pregnancy were about one and a half to two times as likely to have a baby with a heart defect as women who received other antidepressants or women in the general population. The most common defects were atrial and Ventricular septal defects that ranged in severity from minor, self-resolving defects to serious defects that required surgical repair.

The FDA said that in one of the studies, the risk of heart defects in babies whose mothers had taken Paxil early in pregnancy was about 2%, compared with a 1% expected risk in the general population. In the other study, the risk of heart defects in babies whose mothers had taken Paxil in the first three months of pregnancy was 1.5% compared to 1% risk for women taking other antidepressants.

The FDA said it asked Paxil’s manufacturer, GlaxoSmithKline, to change the drug’s label to upgrade the pregnancy warning from a category C to a category D, a higher level warning. The company changed the label two months ago to add data from one of the studies. The latest label change reflects data from both studies, the FDA said.