Researchers from Boston University’s Slone Epidemiology Center have found that certain selective serotonin reuptake inhibitors antidepressants do not appear to increase the risk for most kinds of birth defects. The findings, to be published in the June 28, issue of the New England Journal of Medicine, suggest that individual SSRIs may increase the risk for some specific defects, but these are rare and the absolute risks are small.

The risk of birth defects following antenatal exposure to SSRIs remains controversial. Early studies demonstrated that SSRIs didn’t increase risks of birth defects when such defects were studied as a group. However, birth defects are not a single entity and individual defects have distinct causes. And, more recent studies have reported elevated risks for some birth defects.

Using data from the Slone Epidemiology Center’s Birth Defects Study, an ongoing program of case-control surveillance of medication use in relation to birth defects, the researchers considered relationships between first trimester SSRI use and the risk of various birth defects among mothers of 9,849 infants with birth defects and 5,860 infants without defects.

The researchers analyzed defects previously linked to SSRI use and found overall SSRI use was not associated with significantly increased risks of craniosynostosis (where connections between skull bones close prematurely), omphalocele (intestines or other abdominal organs protrude from the naval) or heart defects overall.

Analysis of individual SSRIs and specific defects showed 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 another paper, from the CDC’s National Birth Defects Prevention Study, in this week’s NEJM. However, the BU researchers stress that even if a specific SSRI increased rates four-fold, as was observed for some of these associations, the risk of having an affected child would be less than one percent.

“Our analyses did not confirm previously reported associations between overall use of SSRIs and a number of birth defects,” said lead author Carol Louik, ScD, an assistant professor at the Slone Epidemiology Center at Boston University. “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.
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Funding for this study was provided by GlaxoSmithKline, the manufacturer of Paxil, the National Institute of Child Health and Human Development, the National Heart, Lung and Blood Institute, Aventis and Sanofi-Pasteur.

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