Infections That Can Affect Pregnancy: Bacterial Vaginosis

What is bacterial vaginosis?

Bacterial vaginosis (commonly known as BV) is the most common vaginal infection in women of childbearing age. It's caused by an imbalance in the bacteria that live in your vagina. About 1 in 5 women have this infection at some point during pregnancy, though estimates vary widely.

Normally, "good" bacteria, called lactobacilli, are in the majority and keep other kinds of bacteria in check. You end up with BV when there are too few lactobacilli, allowing other bacteria to grow out of control. No one knows for sure what causes the balance of bacteria to change.

How does having BV affect my pregnancy?

Having BV when you're pregnant is associated with an increased risk of preterm birth and having a low-birth-weight baby, preterm premature rupture of the membranes (PPROM), <> and uterine infection after delivery. A few studies show a connection between BV and second-trimester miscarriage.

But the link between BV and pregnancy complications isn't perfectly clear. Experts don't yet know why only some women with BV end up delivering prematurely. They also don't know if BV directly causes complications such as PPROM or if women who are predisposed to other infections or problems that may lead to these complications are also more likely to have BV.

That said, many women with BV have perfectly normal pregnancies. And up to half of the cases of BV in pregnant women resolve on their own.

Having BV does make you more susceptible to certain sexually transmitted infections (STIs), such as chlamydia, gonorrhea, and HIV, if you're exposed to them. In women who aren't pregnant, BV has been linked to an increased risk of pelvic inflammatory disease (PID) and infections after gynecologic surgery. (It's possible to get PID during pregnancy, but it rarely happens.)

What are the symptoms of BV?

At least half the women who get BV have no symptoms at all. If you do have symptoms, you might notice a thin white or gray discharge with a foul or fishy smell. This odor is most apparent after sex, when the discharge mixes with semen. You may also have burning when you urinate or irritation in your genital area, though this isn't common.

Let your healthcare provider know if you have these symptoms. She'll examine a sample of your vaginal fluid and cervical secretions to see if you have BV or another infection, and she'll prescribe medication accordingly.

Will I be screened for BV if I don't have symptoms?

It depends. If you don't have symptoms and are at low risk for giving birth prematurely, you won't be screened for BV. If you're at high risk for delivering prematurely (particularly if you've had a premature baby in the past), you might be screened at your first prenatal visit and, if positive, treated.

Although women with BV are more likely to have a preterm delivery and antibiotics can clear up the infection most of the time, almost all research to date shows that treating symptom-free cases of BV in women who haven't had a previous preterm delivery doesn't lower their chances of delivering early. For this reason, the U.S. Preventive Services Task Force (USPSTF), the Centers for Disease Control and Prevention (CDC), the American College of Obstetricians and Gynecologists (ACOG), the American Academy of Family Physicians (AAFP), and a number of other experts agree for now that screening isn't worthwhile for this group of women.

If you don't have symptoms of BV but are at high risk for preterm delivery, your caregiver may or may not screen you at your first prenatal visit. Experts debate whether it's beneficial to do so because the evidence is conflicting.

Some studies have found that screening and treating women who've previously had a preterm delivery reduces their risk of giving birth early, but other research has shown it makes no difference. In a study of women with no symptoms who'd had a second-trimester miscarriage or preterm labor in a prior pregnancy, treatment actually increased the risk of preterm birth.

In a 2008 statement, the USPSTF concluded that for women who are at high risk for preterm delivery but have no symptoms of BV, "the current evidence is insufficient to assess the balance of benefits and harms of screening for bacterial vaginosis." There are some specialists, though, who recommend screening for certain high-risk women. And everyone agrees that more research is needed in this area, so stay tuned.

How is BV treated during pregnancy?

If you're diagnosed with BV, you'll be given a course of antibiotics that are considered safe to take during pregnancy. (Unlike with some other infections, your partner won't be treated.)

It's important to take all of the medicine that you've been prescribed, even if any symptoms have gone away. In most cases, this will clear up the infection in your vagina and any symptoms you might have, though unfortunately the infection may recur at some point.

In fact, up to 30 percent of women have symptoms again within three months. Antibiotics usually kill off most of the bacteria that cause BV, but there's no way to get the "good" bacteria to grow back faster so they can hold the "bad" bacteria in check. Let your practitioner know if your symptoms come back.

How can I avoid getting BV?

Because no one knows what causes this bacterial imbalance, there's nothing definitive you can do to protect yourself from bacterial vaginosis. However, there are a few ways you can reduce your risk of getting BV:

• Follow safe-sex practices if either you or your partner has sex with other people. It's not clear what role sexual activity plays in triggering BV, but it's rare in women who've never had sex and is most common in women with multiple sex partners and new sex partners. It's also prevalent among gay women.
  
• If you smoke, here's another reason to quit: Smoking cigarettes increases your risk for BV.
  
• Don't douche or use feminine hygiene sprays or scented soaps on your genitals. These products may upset the delicate balance of bacteria in your vagina. (You shouldn't douche during pregnancy anyway. In extremely rare cases, douching may force air to pass beneath the membranes of the amniotic sac and enter your circulation, causing an air embolism that can be life threatening.)