Bacterial Vaginosis (BV)
What it is: An imbalance of bacteria in your vagina. It's the most common vaginal infection in women of childbearing age. In the U.S., as many as 16 percent of pregnant woman have BV, according to the CDC.
Why it's dangerous: It increases your risk for preterm labor and birth, says Paul Nyirjesy, MD, professor of obstetrics and gynecology at the Drexel University College of Medicine, in Philadelphia. A 2002 study also found that women with BV were about 20 percent more likely to suffer a miscarriage in their second trimester.
Should you be tested? Experts don't recommend screening all pregnant women unless they have clear symptoms, such as a strong fishlike odor and/or a thin white or gray discharge. "Research shows that treating women who are symptomless doesn't reduce risk of premature delivery," explains Patrick Duff, MD, professor and residency program director in the department of obstetrics and gynecology at the University of Florida, in Gainesville. The one exception? Women with a history of giving birth prematurely should be tested.
Treatment: A seven-day course of the oral form of the antibiotic metronidazole (Flagyl).