Risk of miscarriage for pregnant users of pivmecillinam: a population-based case-control study

Few data exist on the risk of miscarriage after exposure to pivmecillinam. We therefore conducted a population-based case-control study in a Danish county with 0.5 million inhabitants during the period 1997-2002. We included 1,599 women with a miscarriage recorded in the Hospital Discharge Registry and selected 10 controls per case among primiparous women who had a live birth during the study period. Controls were selected from the Danish Medical Birth Registry. We obtained data on use of pivmecillinam and sulfamethizole from a prescription database. Five cases (0.30%) and 24 controls (0.15%) were exposed to pivmecillinam in the last week before the miscarriage/index date. After adjustment for maternal age, use of antidiabetics or antiepileptics, the odds ratio for miscarriages among users of pivmecillinam compared with non-users was 2.03 (95% confidence interval: 0.77-5.33) and the corresponding odds ratio for use of sulfamethizole was 1.53 (95% confidence interval: 0.76-3.09). Exposure within 2 to 12 weeks before the miscarriage was not associated with an increased risk. We concluded that use of pivmecillinam was associated with an increased risk of miscarriage, but the risk was not significantly (p=0.64) different from the risk associated with use of sulfamethizole.