Aims: To estimate the population-based incidence rates of pregnancy, spontaneous and elective abortions, and birth defects associated with isotretinoin use, and to determine predictors of pregnancy while on isotretinoin.
Methods: Using the RAMQ (medical and pharmaceutical data), MED-ECHO (hospitalizations) and ISQ (births and deaths) databases for the period 1984-2002, a cohort of 8609 women between 13 and 45 years of age and with a first prescription for isotretinoin (date of entry in the cohort) was identified. Women were eligible if they were insured by RAMQ for their medications at least 12 months before entry in the cohort and until 1 month after the end of their isotretinoin treatment. Pregnancies, spontaneous and elective abortions, and birth defects were identified using procedure codes and medical diagnoses.
Results: Of the 8609 women included, 90 became pregnant, an annual incident pregnancy rate during isotretinoin treatment of 32.7 per 1000 person-years of treatment (95% confidence interval 26.6, 40.1). Of the 90 women who became pregnant while on the drug, 76 terminated the pregnancy (84%), three had a spontaneous abortion (3%), two had trauma during delivery resulting in neonatal deaths (2%) and nine had a live birth (10%). Among the live births, only one had a congenital anomaly of the face and neck (11%). Adjusting for potential confounders, predictors of becoming pregnant while on isotretinoin were lower socio-economic level, one or more visits to the doctor or to the emergency department, or one or more hospitalization while on isotretinoin; concomitant isotretinoin and oral contraceptive use had a preventive effect.
Conclusions: This first non-interventional population-based study generated incidence rates of pregnancy while on isotretinoin four times greater than what has been reported in the literature thus far; elective abortion rates were also much higher in our study. This shows the importance of using population-based data for public health purposes.