Using a common medication to treat vaginal yeast infections during pregnancy could be associated with an increased risk of miscarriage, researchers warned.

While topical treatments are used as the first line for pregnant women with fungal infections, oral drug fluconazole is also used during pregnancy. The study, published in the journal Canadian Medical Association Journal, showed pregnant women who took oral version of the drug fluconazole were more likely to experience miscarriage than those who did not.

"Our study shows taking oral fluconazole during pregnancy may be associated with higher chances of miscarriage," said Anick Berard from the University of Montreal, Canada. Higher doses of oral fluconazole (over 150 mg) during early pregnancy may also be linked with higher chances of giving birth to a baby with heart defect, she added.

The study re-emphasises safe practices during pregnancy, which include correct diagnosis and choosing the safest medication with the largest body of data. For the study, researchers studied data on 441,949 pregnancies. During pregnancy women often get thrush -- a yeast infection caused by the Candida species of fungus, usually Candida albicans -- because of changes going on in the body, especially during the third trimester.

Thrush during pregnancy can be treated with cream or a tablet inserted in the vagina (a pessary) that contains clotrimazole or a similar antifungal drug. While thrush can also be treated with fluconazole, it should not be taken during pregnancy, or even those trying to get pregnant or breastfeeding, according to the UK National Health Service (NHS).