NEW YORK, Jul 23 (Reuters Health) -- Bacterial vaginosis -- inflammation of the vagina linked to bacterial infection -- "is associated with an increased risk of miscarriage in the first trimester in women undergoing in vitro fertilization," write British researchers in the July 24th issue of the British Medical Journal.

The investigators also suggest that bacterial vaginosis may be a risk for naturally conceived pregnancies.

Bacterial vaginosis occurs when healthy bacteria populating the vagina become displaced -- for reasons that remain unclear -- by unhealthy species that cause inflammation, itching and burning in the affected area. According to gynecologic experts, bacterial vaginosis is the most common cause of abnormal vaginal discharge in women of childbearing age.

Previous studies have linked bacterial vaginosis with increased risks for preterm delivery in pregnant women. To determine if infections might raise risks for miscarriage, Dr. Susan G. Ralph and colleagues at the General Infirmary at Leeds, UK, tested 771 women conceiving through in vitro fertilization (IVF) for signs of the bacterial vaginosis. IVF patients were chosen for the study because researchers could track their infection status from conception straight through to delivery.

The presence of bacterial vaginosis did not appear to affect conception, the authors report.

However, risks for miscarriage during the first 3 months of pregnancy were twice as high among infected women versus non-infected women, according to the researchers. Overall, nearly a third (31.6%) of the 190 study subjects diagnosed with bacterial vaginosis experienced miscarriage in their first trimester, compared with just 18.5% of non-infected women. This finding remained significant even after adjusting for risk factors such as previous history of miscarriage, maternal age, and smoking.

The exact links between bacterial vaginosis and miscarriage remain unclear. Ralph and colleagues note that the majority of miscarriages occurred within the first 6 weeks of conception. These types of early pregnancy failures are often associated with "a failure of implantation or early embryonic development" linked to endometritis -- an inflammation of the uterus.

Endometritis is a common complicating factor for all pregnant women, regardless of their method of conception. If endometritis does play a role in raising miscarriage rates among women infected with bacterial vaginosis, the study findings might therefore apply "to all women trying to conceive," the authors conclude. They urge further studies aimed at determining whether prevention of bacterial vaginosis during pregnancy can reduce a woman's risk for miscarriage.

SOURCE: British Medical Journal 1999;319:220-223.

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