Pregnancy outcome following first-trimester exposure to zopiclone: a prospective controlled cohort study.

Objective: Zopiclone, a cyclopyrrolone derivative, is a short-acting hypnotic. To date, no published data exist regarding human pregnancy experience with zopiclone. The purpose of this study was to compare pregnancy outcome following first-trimester exposure to zopiclone with that of a matched control group of women, who were counseled for nonteratogenic exposure.

Methods: The Motherisk Program, the Toronto Teratogen Information Service, prospectively collected and followed up 40 women exposed to zopiclone during pregnancy. Pregnancy outcome was compared with that of a matched control group of women, who were counseled for nonteratogenic exposure.

Results: There was no increase in the rate of major malformations (0 of 31 [0%] for zopiclone vs. 1 of 37 [2.7%] for nonteratogenic controls; p = 1).

Conclusions: Our study, which is the first cohort on zopiclone use during embryogenesis, albeit small, suggests that zopiclone does not appear to be a major human teratogen. Larger studies are needed to establish its safety during pregnancy.