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.