There are several infections that can increase a woman's risk for preterm labor, and your doctor can test you for each. This section discusses screening for one of these infections, bacterial vaginosis, or BV, since it is the most common infection associated with preterm labor. Researchers don't understand why women with BV are at increased risk-it may be that BV causes early labor, or it may be that women who get BV have a difference in the way their body works that puts them at risk for preterm birth.

How Is the Test Done?

To find out if you have BV, your care provider performs a pelvic exam to look for vaginal discharge. He or she also takes a sample of your vaginal secretions and the cells lining the vagina to send to a laboratory for testing. If the exam and tests meet three of the following four criteria, you are diagnosed with BV:

  • vaginal discharge is present;
  • the discharge has a pH of > 4.5 (pH measures how acidic or alkaline a substance is);
  • the vaginal secretions have a fishy odor (to test for this, a laboratory technician performs a ?whiff test? by adding a solution of 10% potassium hydroxide to a slide containing vaginal secretions); or
  • when examined under a microscope, the cells lining the vagina are heavily coated with bacteria.

How Effective Is Testing for Bacterial Vaginosis?

If you have BV, your risk for preterm delivery is increased but it is not known exactly how much. Nonetheless, it is important to know that you have BV because it can be easily treated with antibiotics (orally for one week). Some studies suggest that treatment reduces the risk of preterm birth, but others do not. In a large review that incorporated all the high-quality studies of BV and preterm birth, treatment with antibiotics seemed to help women who developed BV and had a history of a prior preterm birth. These women were less likely to break their water early (PPROM) and had higher birth weight babies than those who were not treated.

Based on these studies, some doctors test women for BV if they have had an early delivery in the past. It's not clear that screening and treatment are helpful for women who don't have a history of preterm birth. Women with symptoms should be treated regardless of their past history.

Studies testing the effectiveness of an antibiotic vaginal cream (clindamycin) in women with BV did not find a reduction in a woman's risk of preterm delivery. This is probably because the antibiotics did not reach the mother's blood stream and thus could not kill the bacteria growing on the internal wall of the uterus.

When Should BV Screening Be Done?

Currently, doctors have different opinions on this topic. If you have a history of preterm delivery, ask your doctor how he or she conducts screening for BV.

Should Everyone Be Screened and Treated for BV?

Although screening for BV is relatively simple and inexpensive, there is no evidence that treating lowisk women improves their pregnancy outcomes.