A well-known antifungal drug used for vaginal yeast infections may be linked to a slightly increased risk of miscarriage, according to a study of more than 1.4 million Danish pregnancies.
Of the more than 3,300 women who took oral fluconazole (Diflucan) in the 7th through 22nd week of pregnancy, 147 had a miscarriage, compared with 563 miscarriages among the more than 13,000 women who did not take the drug, the researchers found.
"From our study, we can only see that women who have been treated with oral fluconazole more often experience miscarriages than untreated women and women who used a topical [vaginal] antifungal," said lead researcher Ditte Molgaard-Nielsen, an epidemiologist at the Statens Serum Institute in Copenhagen.
However, the study cannot prove that fluconazole causes miscarriages, she said.
"Our findings cannot precisely show whether fluconazole causes miscarriage. We cannot rule out that fluconazole-treated women differ from untreated women in ways that are associated with an increased risk of miscarriage," Molgaard-Nielsen said.
She added that until more data are available on the association between fluconazole and the risk of miscarriage, the drug should be prescribed cautiously to pregnant women.
The report was published in the Jan. 5 issue of the Journal of the American Medical Association.
Vaginal yeast infections are common during pregnancy. In the United States, it is estimated that 10 percent of pregnant women will develop one. Treatment is either a topical antifungal cream or the oral drug fluconazole, Molgaard-Nielsen said.
"Topical antifungals (vaginal suppositories) are first-line treatment for pregnant women, but a small number of pregnant women receive oral treatment with fluconazole, for example in cases of recurrence, severe symptoms, or when topical treatment fails. But oral fluconazole may also be used as first treatment by personal preference," she said.
Dr. Jennifer Wu, an obstetrician and gynecologist at Lenox Hill Hospital in New York City, said that fluconazole is the only oral drug used to treat yeast infections.
"Women who are trying to become pregnant or who are pregnant should avoid fluconazole," Wu said. "For these women, a topical medicine is the preferred treatment."
The researchers also looked at the association between fluconazole and stillbirth. Although fluconazole was tied to an increased risk of miscarriage, it did not significantly increase the risk of stillbirth, Molgaard-Nielsen said. Among the more than 5,300 women who took fluconazole from the 7th week of pregnancy to birth, 21 had a stillbirth, compared with 77 stillbirths among the more than 21,500 women who did not use the drug.
"Although the risk of stillbirth was not significantly increased, this should be investigated further," she added.
For the study, Molgaard-Nielsen and colleagues collected data on more than 1.4 million pregnancies from 1997 to 2013. They compared women who used oral fluconazole during pregnancy to those who didn't.
Dr. Jill Rabin, the co-chief of the division of ambulatory care at the Women's Health Programs-PCAP Services at Northwell Health in New Hyde Park, N.Y., said she prefers using topical treatments for yeast infections because of the side effects of fluconazole, such as flu-like symptoms.
Rabin said that all vaginal yeast infections are not the same and treatment needs to be targeted to the specific type of infection.
Moreover, symptoms that appear to be a yeast infection may be something else, she added. "Women should not assume that if they have a discharge and an itch that it is a yeast infection," Rabin said.
Rabin cautioned against trying to treat these symptoms with over-the-counter drugs. "Women should not try to treat themselves, especially if they are pregnant," she said. "You want to call your doctor, not Doctor Google."