INTRODUCTION: Misoprostol can be used in the prevention of gastric ulcer in treatment with diclofenac and is used in rheumatic diseases. Since misoprostol causes contractions of the uterus, it can also be used to induce abortions when administrated vaginally. The aim of the study was to investigate if early pregnancy exposure to oral diclofenac/misoprostol was associated with miscarriage.

METHOD: We conducted a nationwide cohort study identifying all registered pregnancies in Denmark from 1997 to 2011. All births were identified using the Medical Birth Registry, and all records of induced abortion and miscarriage were from the National Hospital Register. Data on drug use were from the National Prescription Register. Cox proportional hazard regression models were used to calculate the hazard of miscarriage in women exposed to diclofenac/misoprostol in early pregnancy.

RESULT: We identified 1,338,824 pregnancies (970,491 births, 142,147 miscarriages, 226,145 induced abortions). One hundred sixty-six were exposed to diclofenac/misoprostol in the early pregnancy of which 28.3 % (47) ended up in a miscarriage compared to 10.6 % among unexposed. The adjusted hazard ratio of having a miscarriage after exposure to diclofenac/misoprostol in the first trimester was 3.6 (CI 95 % 2.6-4.9).

CONCLUSION: We found an increased risk of miscarriage after exposure to diclofenac/misoprostol during the early pregnancy. Women in the fertile age should not be treated with the combination of diclofenac/misoprostol if other options were available.