New research on whether taking antidepressants during pregnancy increases the chance of birth defects in newborns suggests that the risk is low -- but is not able to clear up the questions for good.
The findings, to be published in the New England Journal of Medicine, suggest that some antipdepressants may increase the risk for some specific defects. But it also concludes that such birth defects are still rare so the absolute risks are small.
Researchers from Boston University's Slone Epidemiology Center, using data from the centre's Birth Defects Study, considered relationships between taking antidepressants in the first trimester or pregnancy and the risk of various birth defects. They looked at mothers of 9,849 infants with birth defects and 5,860 infants without defects.
The researchers found that the use of drugs called selective serotonin reuptake inhibitors was not associated with significantly increased risks of craniosynostosis (in which connections between skull bones close prematurely), omphalocele (in which intestines or other abdominal organs protrude from the navel) or heart defects, overall.
But there were significant associations between setraline (e.g. Zoloft) and omphalocele and septal defects (defects in the walls that separate the chambers of the heart), and between the paroxetine (e.g. Paxil) and certain heart defects that interfere with blood flow to the lungs.
This last association was also reported in a second paper, from the CDC's National Birth Defects Prevention Study, also in this week's NEJM.
However, the Boston researchers stress that even if a specific SSRI increased rates four-fold, as was observed for some of these associations, the absolute risk of having an affected child would be less than one per cent.
"Our analyses did not confirm previously reported associations between overall use of SSRIs and a number of birth defects," said the lead author of one of the studies, Carol Louik.
"Rather, our study suggests that risks are limited to specific SSRIs in relation to specific birth defects.
"Still, it is important to keep in perspective that the baseline risks for these rare defects are small, so even if the modest increased risks we observed are correct, the chances of having a child with such a defect are quite small," she added.
An accompanying editorial concedes that more research is likely needed.
"Patients and physicians alike would prefer it if there were clear lines separating 'risk' and 'no risk' and if all studies gave consistent results pointing in the same direction," the editorial reads.
"Unfortunately, this is often not the case, and the data to inform potential risks of SSRIs are no exception.
"The two reports in this issue of the Journal, together with other available information, do suggest that any increased risks of these malformations in association with the use of SSRIs are likely to be small in terms of absolute risks."
