Two types of SSRIs (selective serotonin reuptake inhibitors), fluoxetine and paroxetine, have been linked to a small but increased risk of birth defects when taken during early pregnancy, according to a new study published in The BMJ.
The researchers note that if these associations are causal, the risk still remains low, but they call for further studies “to enable women and their health care providers to make more informed decisions about treatment.”
Until now, studies focusing on antidepressant use and birth defects have resulted in conflicting conclusions. This has led to confusion and uncertainty regarding their safety during pregnancy.
There have been many reports of specific birth defects from women taking SSRIs, and these were analyzed further in the current study. To do this, a team of researchers from the U.S. and Canada combined the findings from independent published analyses with data from the U.S. National Birth Defects Prevention Study (NBDPS).
Their analysis included 17,952 mothers of infants with birth defects and 9,857 mothers of infants without birth defects, born between 1997 and 2009.
Use of the SSRI drugs citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac), paroxetine (Paxil), or sertraline (Zoloft) at least once in the period from one month before conception through the third month of pregnancy was taken into account.
Women who had taken antidepressants other than SSRIs or had pre-existing diabetes were excluded from the analysis.
Sertraline (Zoloft) was the most commonly used SSRI, but none of the five previously reported associations between sertraline and birth defects were confirmed. This is reassuring, say the authors, as about 40 percent of women reporting use of an SSRI in early pregnancy used sertraline.
For nine other previously reported associations between maternal SSRI use and birth defects in infants, the analysis showed no associations.
However, two previously reported birth defects associated with fluoxetine treatment were found: heart wall defects and irregular skull shape (craniosynostosis).
Five previously reported birth defects associated with paroxetine (Paxil) treatment were also seen. These included heart defects, problems with brain and skull formation (anencephaly), and abdominal wall defects.
The findings provide reassuring evidence for some SSRIs, say the researchers, but suggest that some birth defects occur more frequently among children whose mothers were taking paroxetine or fluoxetine in early pregnancy.
“Although our analysis strongly supports the validity of the associations that were observed, the increase in the absolute risks, if the associations are causal, is small,” said the researchers.
For example, the absolute risks in the babies of mothers who are treated with paroxetine early in pregnancy would increase for anencephaly from two per 10,000 to seven per 10,000, and for one of the heart defects from 10 per 10,000 to 24 per 10,000.
“Continued scrutiny of the association between SSRIs and birth defects is warranted,” they said. “Meanwhile, the current analysis provides guidance to the safest treatment options during early pregnancy to minimize the risk of major birth defects, while providing adequate treatment of maternal depression,” they conclude.