Chorioamnionitis is an infection of the amniotic membranes or fluid, the placenta, or the umbilical cord. Bacteria such as E. coli or group B strep are the most common invaders. Because bacteria can enter the amniotic fluid once it's ruptured, women who have premature rupture of the membranes (PROM) or prolonged labors are at increased risk of chorioamnionitis.

Here's what expectant moms need to know about this infection, including the signs to watch for and treatment options.

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Key Takeaways
  • Chorioamnionitis is an uncommon but serious infection that affects pregnancy tissues. It's a bacterial infection of the amniotic fluid, membranes, placenta, or umbilical cord. Chorioamnionitis occurs in about 1% to 5% of pregnancies and can develop when bacteria (commonly coli or group B strep) enter the amniotic sac.
  • Certain situations increase risk and symptoms require quick attention. Risk is higher with prolonged labor or when the membranes rupture early, allowing bacteria in. Key warning signs include fever, rapid heart rate (in mom and baby), uterine tenderness, and foul-smelling fluid — symptoms that should prompt immediate medical care.
  • Treatment is effective, but early delivery is sometimes necessary. Chorioamnionitis is treated with antibiotics during and after delivery, and outcomes are often good when treated promptly. In more severe cases, early delivery may be necessary to protect the baby and prevent complications like preterm labor or newborn infection.

What is chorioamnionitis?

Chorioamnionitis, also called intraamniotic infection, is bacterial infection that can develop when bacteria enter:[1]

  • The amniotic membranes or fluid that surround and protect your baby
  • The placenta
  • The umbilical cord

The infection occurs in 1% to 5% of pregnancies. It's been linked to preterm labor and can put your baby at risk for infection, so it's important to call your practitioner right away if you notice any of the symptoms above.

What causes chorioamnionitis?

Most commonly, chorioamnionitis is caused by bacteria such as E. coli or by the group B streptococci (GBS), which you'll be tested for around week 35 of your pregnancy.

Women who experience premature rupture of membranes (PROM) are at increased risk for chorioamnionitis because bacteria can enter the amniotic once it has ruptured. A longer labor also raises the risk.

Keep track of your symptoms and appointments, get expert advice, and connect with other moms with similar experiences in the What to Expect app.

What are the symptoms of chorioamnionitis?

The symptoms of chorioamnionitis may include:

  • Fever
  • An increased heart rate in both you and your baby
  • A tender or painful uterus
  • Leaking, foul-smelling amniotic fluid

Your practitioner may diagnose chorioamnionitis based on your symptoms. If your membranes haven't fully ruptured but infection is suspected, you may have amniocentesis to test the amniotic fluid.[2]

Because the risk increases with prolonged rupture of the membranes, seek care right away. In some full-term pregnancies, a mother's water may break before contractions begin. While it can be normal to wait for labor to start, delays may increase the risk of infection.

How is chorioamnionitis treated?

Chorioamnionitis can be serious, but treatment is available. If you're diagnosed with chorioamnionitis, you'll likely be prescribed antibiotics to clear the infection. You and your baby will also be given antibiotics after delivery to prevent further complications.

"I was given antibiotics for chorioamnionitis during my labor and was completely fine after labor was over," says What to Expect Community mom MarineWife2002. "My daughter was fine. She didn't catch it, though she was given antibiotics right away just in case."

"I was diagnosed with chorio when my son was born," says Community member BabyAJ23. "I was told it was a uterine infection and had a C-section. My baby didn't get it, but I needed IV antibiotics for two days after he was born."

If the infection is severe or if your baby's health is at risk, early delivery — even if premature — may be the safest option.[3]

What should I do if I suspect chorioamnionitis?

If you notice any leaking of amniotic fluid, no matter how small, call your practitioner so that they can determine if your membranes have ruptured.

If you can't tell if you're leaking amniotic fluid, take the sniff test: Urine typically smells like ammonia, while amniotic fluid has a milder or slightly sweet smell — and may smell foul if infected. Always call your practitioner if you have any doubt.