STUDY QUESTION

Are women who fill a benzodiazepine prescription before conception at increased risk of ectopic pregnancy?

SUMMARY ANSWER

Risk of ectopic pregnancy is 50% higher among women who fill a benzodiazepine prescription before conception.

WHAT IS KNOWN ALREADY

Benzodiazepine use in pregnancy increases the risk of miscarriage, adverse birth outcomes and adverse child development outcomes.

STUDY DESIGN, SIZE, DURATION

Using data from US commercial insurance claims, we performed a cohort study of 1 691 366 pregnancies between 1 November 2008 and 30 September 2015.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We identified ectopic pregnancies using diagnosis and procedure codes and used unadjusted and inverse probability of treatment (IPT)-weighted log-binomial models to calculate relative risks (RR) of ectopic pregnancy for pregnant women who did and did not fill any prescriptions for benzodiazepines in the 90 days before conception. Two sub-groups of women with specific indications for benzodiazepine use were also examined—women who had a least one diagnosis for anxiety disorder and women who had at least one diagnosis of insomnia in the year before conception.

MAIN RESULTS AND THE ROLE OF CHANCE

Of the 1 691 366 pregnancies, 1.06% filled at least two benzodiazepine prescriptions totaling at least 10 days supply in the 90 days before conception. Among women with a benzodiazepine prescription, there was an excess of 80 ectopic pregnancies per 10 000 pregnancies, and their IPT-weighted risk of ectopic pregnancies was 1.47 (95% CI 1.32 to 1.63) times greater relative to women without benzodiazepine prescriptions before conception. The IPT-weighted RR between ectopic pregnancy and benzodiazepine use was 1.34 (95% CI 1.18 to 1.53) among women with anxiety disorder diagnoses and 1.28 (95% CI 0.99 to 1.68) among women with an insomnia diagnosis.