Chorioamnionitis is a bacterial infection that occurs before or during labor. The name refers to the membranes surrounding the fetus: the “chorion” (outer membrane) and the “amnion” (fluid-filled sac).

The condition occurs when bacteria infect the chorion, amnion, and amniotic fluid around the fetus. It can lead to a preterm birth or serious infection in the mother and the baby. It’s most commonly seen in preterm births; it’s also seen in approximately 2 to 4 percent of full-term deliveries.

Chorioamnionitis is also known as “amnionitis” or “intra-amniotic infection.”

This condition usually develops because of an infection that can occur when bacteria that are normally present in the vagina ascend into the uterus, where the fetus is located.

E. coli, group B streptococci, and anaerobic bacteria are the most common causes of chorioamnionitis.

The amniotic fluid and placenta — and baby — can become infected.

Chorioamnionitis doesn’t always cause symptoms, but some women may experience:

The most common risk factors for this condition include:

If you have one or more of these risk factors, you may be more likely to develop chorioamnionitis.

Chorioamnionitis is usually considered a medical emergency. The condition can lead to serious complications, including:

About 3 to 12 percent of women with chorioamnionitis have bacteremia. This condition also increases the need for a cesarean delivery. Of those who have a cesarean delivery, up to 8 percent develop a wound infection and approximately 1 percent develop a pelvic abscess (collection of pus). Maternal death due to infection is extremely rare.

Babies delivered to mothers with chorioamnionitis are also in danger of serious complications:

  • The condition can lead to meningitis (an infection of the lining of the brain and spinal cord). However, this occurs in less than 1 percent of infants who are delivered to term.
  • Pneumonia or bacteremia may also develop in about 5 to 10 percent of babies born to women with chorioamnionitis. Bacteremia is more common in preterm infants.

In rare cases, the complications associated with chorioamnionitis can be life-threatening to preterm infants.

These complications are less likely to occur if the infection is diagnosed early and antibiotic treatment is started.

Your doctor can usually diagnose this condition by performing a physical examination. Laboratory tests can confirm that diagnosis.

Amniocentesis may be necessary if you’re in preterm labor. In this prenatal test, a small amount of amniotic fluid is removed for testing. You may have chorioamnionitis if the amniotic fluid has a low concentration of glucose (sugar) and a high concentration of white blood cells (WBCs) and bacteria.

Once you’re diagnosed with chorioamnionitis, you’ll be treated immediately to prevent complications.

Early treatment can bring down your fever, shorten your recovery time, and lower your baby’s risk of infection and complications.

Antibiotics are commonly used to treat the condition. They’re usually given through an IV and are continued until you’ve delivered your baby. You may receive some of the following antibiotics:

When the infection is responding to treatment, your doctor will stop administering antibiotics. You’ll be able to leave the hospital after you no longer have a fever and your doctor feels you can safely go home.

Most people don’t require oral antibiotics on an outpatient basis.

The long-term outlook for mothers with chorioamnionitis is excellent. Future fertility is rarely compromised.

The outlook for infants delivered to infected mothers is also very good.

But some babies, particularly those who are preterm, may have long-term complications. These complications can include lung disease or impaired brain function.

Your doctor will make every effort to prevent the infection from developing in the first place. They can do this in several ways, such as:

  • screening you for bacterial vaginosis (vaginal inflammation) in your second trimester
  • screening you for group B streptococcal infection once you reach 35 to 37 weeks of pregnancy
  • reducing the number of vaginal examinations performed during labor
  • minimizing the frequency of internal monitoring

It’s important to attend regular checkups with your doctor and address your questions and concerns.