First trimester diclofenac exposure and pregnancy outcome.

Objective: To assess the safety of diclofenac during pregnancy.

Methods: A prospective observational cohort study, evaluating follow-up data of women who contacted Teratology Information Services to get counseling. The exposed group included 145 pregnant women who were exposed to diclofenac between the 5th and the 14th gestational week. A contemporary control group (501 women) was randomly selected from among patients who contacted Teratology Information Services with regard to exposures to agents known not to be teratogenic during a similar period of pregnancy.

Results: Major birth malformations were not more common in the study group than in the control group (p=0.07).

Conclusion: Our study suggests that the use of diclofenac is relatively safe during the first trimester of pregnancy and the studied sample size makes it possible to exclude a risk of congenital malformation higher than 3.3, with a power of 80%.