Prescriptions filled during pregnancy for drugs with the potential of fetal harm.

OBJECTIVE: To assess the extent of prescriptions filled by pregnant women for drugs with recognised potential of fetal harm, and to document the outcomes of these pregnancies.

DESIGN: Cross-sectional study.

POPULATION: Quebec Pregnancy Registry.

METHODS: We identified women who were pregnant during a five-year period and who were insured for prescription medications under the provincial drug plan. We obtained information on prescriptions filled during pregnancy for drugs with known potential of fetal harm.

MAIN OUTCOME MEASURES: Prescriptions filled for study drugs during the first, second and third trimesters of pregnancy; termination of pregnancy (TOP) or delivery, and whether the baby was diagnosed with a major congenital malformation (MCM).

RESULTS: Of 109 344 women, 56% filled at least one prescription for a medication during pregnancy; 6.3% filled at least one prescription for a drug known to pose a risk to the fetus. Overall, 47% (95% CI, 45.8-48.2) of pregnancies exposed to drugs under study ended in TOP versus 36.2% (95% CI, 35.9-36.5) of those not exposed; 8.2% (95% CI, 8.0-10.0) of live births were diagnosed with an MCM during the first year of life versus 7.1% (95% CI, 6.9-7.3) of those not exposed.

CONCLUSIONS: This study documents an important level of prescriptions filled during pregnancy for drugs harmful to the developing fetus. The proportions of both TOPs and babies born with MCMs were elevated compared with the expected values. Clinicians caring for women during pregnancy should conduct a medication inventory prior to a planned pregnancy, or as soon as an unplanned pregnancy is recognised.