A common over-the-counter thrush medication more than doubles a woman’s risk of miscarriage if taken in early pregnancy, a study shows.

Oral fluconazole, used to treat vaginal yeast infections, was linked to a twofold risk of miscarriage at low dose, and three times the risk at high dose, the Canadian study shows.

In addition, a dose higher than 150mg increased the risk of cardiac septal closure anomalies by 80%, the study found.

The researchers carried out a nested case-control study, matching pregnant women who filled prescriptions for oral fluconazole to controls from a cohort of nearly half a million pregnancies.