What is already known about this subject
• As of now, no population-based data exist on the incidence of pregnancy, elective abortions, and birth defects while on isotretinoin.
• From surveys or interventional studies, it is known that pregnancy rates while on isotretinoin are comparable to the baseline rate, and that birth defect rates associated with first-trimester exposure are 10 times greater than in the general population.
• Given that women decide to terminate pregnancies based on the available data, population-based estimates are needed.
What this study adds
• This first non-interventional population-based study on the risk of pregnancy while being exposed to isotretinoin has shown that the rate of pregnancy is four times greater than what has been published to date (32.7/1000 person-years).
• Any pregnancy while using isotretinoin is the result of a failure of pregnancy prevention strategies, hence, thus far, pregnancy prevention programmes have failed.
• The rate of elective abortions is much higher than previously reported (84%).
• Women of a lower socio-economic level and high users of healthcare services are more likely to become pregnant while on isotretinoin, suggesting that high use of health services increase the opportunity of having a prescription for isotretinoin or of having a pregnancy diagnosis.
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.
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.
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.
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.