A Deeper Shade of Blue

There is research to support the reproductive safety of certain antidepressants, including Prozac (fluoxetine) and the older tricyclic antidepressants. Less information on reproductive safety is available for the newer antidepressants. A recent study form researchers at the Motherisk Program in Toronto has looked at outcomes in infants exposed to the antidepressant mirtazapine (Remeron) in pregnancy. In this study, 104 women took mirtazapine during pregnancy. Two of the infants had major malformations (1.9%). Similar rates of malformation were found in two control groups: women exposed to other antidepressants and women exposed to non-teratogens (for example, Tylenol). In the mirtazapine group, there was one stillbirth, 20 spontaneous abortions, and six therapeutic abortions.

The authors noted  that “as in previous studies on antidepressants in pregnancy, there were higher rates of miscarriages in both the mirtazapine group and the comparison group of women taking other antidepressants, than the other comparison group of women who were not.” These findings were not statistically significant. The number of births before 37 weeks was significantly higher in the mirtazapine group (10%) than the non-teratogen group (2%). It was also elevated in the other antidepressant group (7%).

These preliminary results suggest that there is no increase in risk of congenital malformations among infants exposed to mirtazapine. While these data are reassuring, it should be noted that, in order to detect a two-fold increase in the prevalence of a given malformation, it is necessary to collect at least 400 to 600 exposures. Thus, further studies are required.

Djulus J, Koren G, Einarson TR, Wilton L, et al. Exposure to Mirtazapine During Pregnancy: A Prospective, Comparative Study of Birth Outcomes. J Clin Psychiatry 2006; 67(8):1280-1284.