Oral fluconazole is commonly used during pregnancy. Researchers explored the effects of exposure to low and high doses of fluconazole during pregnancy upon occurrence of spontaneous abortions, major congenital malformations and stillbirths. Using a case control approach, within a cohort of 441 949 pregnancies, 320 868 pregnancies were included in the analyses of spontaneous abortions, 226 599 of major congenital malformations and 7832 of stillbirths. Most (69.5%) women who used fluconazole in pregnancy received the common single therapeutic dose of 150 mg (low dose); but some received a dose of > 150 mg (high dose). Use of oral fluconazole during early pregnancy was associated with an increased risk of spontaneous abortion compared with no exposure (OR for low-dose treatment 2.23, 95% confidence interval [CI] 1.96–2.54; OR for high-dose treatment 3.20, 95% CI 2.73–3.75). Exposure to fluconazole during the first trimester did not increase the risk of overall major congenital malformations; but high dose treatment during the first trimester was associated with an increased risk of cardiac septal closure anomalies (OR 1.81, 95% CI 1.04–3.14). No association was found between exposure to fluconazole during pregnancy and the risk of stillbirth. The practice of treatment with fluconazole during pregnancy, particularly at high dose or during the first trimester, warrants further consideration. View the original study, published in the CMAJ, here