Associations between low- and high-dose oral fluconazole and pregnancy outcomes: 3 nested case-control studies

While topical azoles are the first-line treatment for fungal infections, oral fluconazole is frequently used during pregnancy. We aimed to assess the effect of exposure to low and high doses of fluconazole during pregnancy on the occurrence of spontaneous abortions, major congenital malformations and stillbirths.

Within the Quebec Pregnancy Cohort (1998-2015), we identified women exposed to low- (≤ 150 mg) and high-dose (> 150 mg) fluconazole, and women who were not exposed. For each case of spontaneous abortion or stillbirth, up to 5 controls were randomly selected using an incidence density sampling method matched on gestational age at diagnosis of spontaneous abortion or stillbirth (index date) and the year of the last menstrual period. For cases of major congenital malformation, we considered all liveborn babies as controls. Generalized estimation equation models were used to analyze the 3 main outcomes separately.

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 exposed to fluconazole in pregnancy received the common single therapeutic dose of 150 mg (low dose); the remainder 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 (adjusted odds ratio [OR] for 345 cases exposed to low-dose treatment 2.23, 95% confidence interval [CI] 1.96-2.54; adjusted OR for 249 cases exposed to 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; however, exposure to a high dose during the first trimester was associated with an increased risk of cardiac septal closure anomalies (adjusted OR 1.81, 95% CI 1.04-3.14; 13 exposed cases) compared with no exposure. No association was found between exposure to fluconazole during pregnancy and the risk of stillbirth.

Any maternal exposure to fluconazole during pregnancy may increase risk of spontaneous abortion and doses higher than 150 mg during the first trimester may increase risk of cardiac septal closure anomalies.