Monogamy May Up Chances a Vaginal Infection Will Recur

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Having multiple sex partners increases the risk of bacterial vaginosis — an imbalance of vaginal bacteria that can cause pain and itching in women — but a new study suggests that being faithful to one partner may cause the infection to recur.

Women in the study who were treated for bacterial vaginosis (BV) were about twice as likely to experience a recurrence if they had sexual intercourse with the same partner before and after treatment, compared to women who had a new sexual partner, or no partner, after treatment.

Antibiotics can cure symptoms of BV in about 80 percent of women. However, in up to 50 percent of women, symptoms come back 3 to 12 months after treatment, the researchers said.

The findings raise an interesting question, the researchers said: Would treating a women's sexual partner for BV at the same time she is undergoing treatment reduce the risk of recurrence?

Bacterial vaginosis results from a decrease in "good" vaginal bacteria, known as lactobacilli, and an increase in "bad" bacteria, known as anaerobes, according to the Mayo Clinic. Doctors do not know exactly what causes this imbalance. One possibility is that, in some cases, the condition "spreads" between partners during sex.

Another possibility is that sexual relations may prevent good bacteria from growing back. However, women who are not sexually active can also develop BV, so the condition is not always linked to sexual behavior.

Studies done in the 1980s tested whether treating a woman's partner would prevent a recurrence of the condition, but these studies were flawed and need to be repeated, said Dr. Jane Schwebke, a professor of medicine at the University of Alabama at Birmingham, who was not involved in the new study.

Schwebke hopes to conduct a study that would examine this issue. "I really think the timing is right to try to do these studies again," she said.

The new study involved 450 women ages 18 to 50 from Melbourne, Australia who had been diagnosed with BV. Each was randomly assigned to receive treatment, with an antibiotic, a probiotic or a placebo. After six months, 115 women (28 percent) experienced a recurrence of bacterial vaginosis. All the women, regardless of which treatment they received, were equally likely to have the condition recur.

Such recurrence of BV was also linked with inconsistent condom use, but not with frequency of sex. Women were 50 percent less likely to experience a recurrence of symptoms if they used hormonal contraceptives, such as the birth control pill or vaginal ring.

This finding suggests hormonal contraception may have a protective effect against the condition, but further research is needed before the medication would be prescribed solely for BV, Schwebke said.

The new study was published online Dec. 12 in the journal Clinical Infectious Diseases.

Pass it on: Women treated for bacterial vaginosis may have a recurrence if they have sex with the same partner before and after treatment.

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.