Chorioamnionitis in Pregnancy: What It Is, Warning Signs, and How It's Treated
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer
Chorioamnionitis is a bacterial infection of the membranes, tissues or amniotic fluid surrounding a fetus during pregnancy, most often caused by E. coli or group B strep. [5] Symptoms include fever, rapid heart rate in you or the fetus and a tender uterus. [5] It is usually treated with IV antibiotics, and when caught quickly, most babies make a full recovery. [5]
What the research says
According to PubMed:
Babies exposed to chorioamnionitis have higher odds of sepsis. In a meta-analysis of 55 studies, histologic chorioamnionitis was associated with confirmed early-onset neonatal sepsis (unadjusted pooled OR 4.42; 95% CI 2.68–7.29), and clinical chorioamnionitis with an OR of 6.82 (95% CI 4.93–9.45). Confirmed sepsis still affected a minority of exposed babies — about 6–7% for early-onset and 22–26% for late-onset sepsis in preterm infants — and the evidence on maternal sepsis was inconclusive (Beck et al., Obstet Gynecol, 2021) [1].
Intra-amniotic infection alone is rarely a reason for cesarean delivery. This practice guidance from the American College of Obstetricians and Gynecologists says that recognizing the infection during labor and starting treatment promptly can minimize illness and death for both the pregnant person and the newborn, and that the infection alone is rarely, if ever, an indication for cesarean delivery (ACOG Committee Opinion No. 712, Obstet Gynecol, 2017) [2].
What Is Chorioamnionitis?
Chorioamnionitis happens when bacteria enter the tissues, membranes or amniotic fluid surrounding a fetus and cause an infection. [5] Chorioamnionitis (intra-amniotic infection) is an infection that happens during pregnancy. It gets its name from the two membranes that surround a fetus: the chorion and the amnion. [5]
Key terms at a glance: The chorion is the outer membrane around a fetus; the amnion is the inner membrane. The placenta is the organ that feeds the growing baby during pregnancy, and amniotic fluid is the fluid that cushions the fetus inside the amniotic sac.
Term | What it means |
Chorioamnionitis | A bacterial infection of the membranes, tissues, or amniotic fluid around a fetus during pregnancy [5] |
Intra-amniotic infection | |
Chorion | The outer membrane that surrounds a fetus [5] |
Amnion | The inner membrane that surrounds a fetus [5] |
Amniotic fluid | The fluid that surrounds and cushions the fetus |
This infection occurs when bacteria enter any of the membranes or tissues around a fetus. These include the chorion (outer membrane), the amnion (inner membrane), the placenta, and the amniotic fluid. [5] [6]
Treatment usually involves getting antibiotics. [5] [6] In some cases, your pregnancy care provider may deliver your baby early. [5] [6] The infection can lead to life-threatening complications in both you and your baby if it is left untreated. [5] [4]
Chorioamnionitis occurs in between 2 and 5 out of every 100 births in the U.S. [5]
What Are the Symptoms of Chorioamnionitis?
Symptoms can vary. Some of the most common are listed below.
What Causes Chorioamnionitis?
A bacterial infection causes chorioamnionitis. [5] The infection can start in your vagina, anus or rectum and spread up to your uterus. [5] It can also begin in your uterus if the amniotic sac ruptures or tears. [5] The bacteria can infect the placenta or the fetus. [5]
Infection can also spread if you have too many vaginal exams after your water breaks or after a procedure like amniocentesis. [5]
The most common bacteria that cause chorioamnionitis are E. coli and group B strep. [5]
What Are the Risk Factors?
Factors that raise your risk include the following.
Risk factor | Why it raises your risk |
Preterm labor | |
Water breaking more than 24 hours before delivery | |
Long labor | |
Vaginal infection or STI | Existing infections can spread up to the uterus [5] |
Group B strep | One of the most common bacteria behind this infection [5] |
Frequent vaginal exams after water breaks | |
Internal fetal monitoring |
How Can I Reduce My Risk?
Chorioamnionitis risk can be lowered with a few simple steps during pregnancy. These include taking antibiotics if your water breaks early, limiting the number of vaginal exams after your water breaks, and getting screened for group B strep in your third trimester. [5]
If you are worried about chorioamnionitis, talk to your pregnancy care provider. They can tell you if you are at risk.
Risk-reduction step | What it does |
Take antibiotics if your water breaks early | Treats bacteria before they can cause an infection [5] |
Limit vaginal exams after your water breaks | Fewer exams mean fewer chances to introduce bacteria [5] |
Get screened for group B strep in your third trimester | Finds a common cause early so it can be treated [5] |
What Are the Complications of Chorioamnionitis?
If you have a serious case of chorioamnionitis, or if it goes untreated, some of the complications affect you, and others affect your newborn.
How Is Chorioamnionitis Diagnosed?
Your pregnancy care provider diagnoses chorioamnionitis based on your symptoms and a physical exam. [5] They may also order several tests.
How Is Chorioamnionitis Treated?
If your provider diagnoses chorioamnionitis, they will give you antibiotics to treat the infection. [5] [6] These are usually given through an IV (a needle in your vein). [5] [6]
In some cases, providers recommend early delivery. [5] [6] This can prevent more problems for you and your baby.
After birth, your baby may also get antibiotics. [5] Some babies may need oxygen to help them breathe or require extra care in a neonatal intensive care unit (NICU). [5]
When Should I See My Healthcare Provider?
Call your pregnancy care provider if your water breaks. [5] You should also call them if you have a fever, abdominal or pelvic pain, or notice a bad smell coming from your vagina. [5]
Can a Baby Survive Chorioamnionitis?
Yes, they can. When the infection is caught and treated quickly, most babies make a full recovery. [5] The exact outcome also depends on how far along you are in pregnancy, how severe the infection is, and whether your baby develops complications before treatment. [5]
What is the bottom line on chorioamnionitis?
Chorioamnionitis is a serious bacterial infection during pregnancy — also called an intra-amniotic infection — that affects the membranes, tissues, or amniotic fluid surrounding the fetus, and can involve the placenta or the fetus itself. It happens in 2 to 5 out of every 100 U.S. births, and the most common culprits are E. coli and group B strep, which can enter after your water breaks, spread up from the vagina, or be introduced during frequent vaginal exams. The warning signs to watch for are fever, a rapid heart rate (in you or the baby), a tender or painful uterus, foul-smelling or unusual vaginal discharge, and sweating. Diagnosis is based on your symptoms and exam, supported by blood and urine tests, vaginal and amniotic fluid cultures, and ultrasound. Treatment is usually IV antibiotics, sometimes with an early delivery, and newborns may need antibiotics, oxygen, or NICU care. With prompt treatment, most babies make a full recovery — so if your water breaks or you develop a fever, pelvic pain, or a bad smell, call your pregnancy care provider right away.
Frequently Asked Questions
What is chorioamnionitis?
A bacterial infection that happens during pregnancy when bacteria enter the tissues, membranes, or amniotic fluid surrounding a fetus. It is also called an intra-amniotic infection.
Why is it called chorioamnionitis?
Chorioamnionitis gets its name from the two membranes that surround a fetus: the chorion (outer membrane) and the amnion (inner membrane).
How common is chorioamnionitis?
Chorioamnionitis occurs in between 2 and 5 out of every 100 births in the U.S.
What causes chorioamnionitis?
A bacterial infection. It can start in your vagina, anus, or rectum and spread up to your uterus, or begin in your uterus if the amniotic sac ruptures or tears.
Which bacteria cause chorioamnionitis?
The most common bacteria are E. coli and group B strep.
What are the symptoms?
Fever, a rapid heart rate in you or the fetus, a tender or painful uterus, vaginal discharge with an unpleasant smell or unusual color, and sweating. Symptoms can vary.
Who is at higher risk?
People going into preterm labor, whose water breaks more than 24 hours before delivery, who have a long labor, a vaginal infection or STI, group B strep, frequent vaginal exams after water breaks, or who need internal fetal monitoring.
Can chorioamnionitis be prevented?
There is no sure way to prevent it, but you can reduce your risk by taking antibiotics if your water breaks early, limiting vaginal exams after your water breaks, and getting screened for group B strep in your third trimester.
Why should vaginal exams be limited after my water breaks?
Infection can spread if you have too many vaginal exams after your water breaks or after a procedure like amniocentesis — each exam can introduce bacteria.
How is chorioamnionitis diagnosed?
Based on your symptoms and a physical exam. Your provider may also order blood and urine tests to check for infection or a high white blood cell count, take a vaginal culture and an amniotic fluid sample to look for bacteria, and use ultrasound to check on the fetus.
How is chorioamnionitis treated?
Usually with antibiotics given through an IV (a needle in your vein). In some cases, providers recommend an early delivery to prevent more problems for you and your baby.
Will my baby get treated too?
After birth, your baby may also get antibiotics. Some babies may need oxygen to help them breathe or extra care in a neonatal intensive care unit (NICU).
What complications can happen?
For you: the infection spreading to your pelvic region and abdomen, endometritis, blood clots in your pelvis or lungs, or sepsis. For your newborn: sepsis, meningitis (inflammation of the membranes around the brain and spinal cord), or pneumonia (a lung infection). Serious complications are less likely with prompt treatment.
Is chorioamnionitis dangerous if left untreated?
Yes. Left untreated, the infection can lead to life-threatening complications in both you and your baby.
Can a baby survive chorioamnionitis?
Yes. When the infection is caught and treated quickly, most babies make a full recovery.
What does the baby's outcome depend on?
How far along you are in pregnancy, how severe the infection is, and whether your baby develops complications before treatment.
What is endometritis?
A complication of untreated or serious chorioamnionitis — an infection of the lining of the uterus.
What is sepsis?
A life-threatening blood infection that both parent and baby can develop.
When should I call my provider?
Call your pregnancy care provider if your water breaks, or if you have a fever, abdominal or pelvic pain, or notice a bad smell coming from your vagina.
What questions should I ask my provider?
Ask whether you are at risk for chorioamnionitis, what group B strep screening involves, and what this condition means for you and your baby. Do not hesitate to ask questions.
How can I lower my baby's risk?
Getting screened for group B strep in your third trimester, taking antibiotics if your water breaks early, and seeking care quickly if warning signs appear are the main ways to reduce risk.
Related Reading
This article is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always seek the guidance of a physician or other qualified health provider with any questions you have about a medical condition. Never disregard professional medical advice or delay seeking it because of something you read here. Chorioamnionitis can lead to life-threatening complications for both parent and baby if left untreated — call your pregnancy care provider if your water breaks, or if you develop a fever, abdominal or pelvic pain, or a bad-smelling vaginal discharge.
References
Beck C, Gallagher K, Taylor LA, et al. Chorioamnionitis and risk for maternal and neonatal sepsis: a systematic review and meta-analysis. Obstet Gynecol. 2021;137(6):1007-1022. PMID 33957655. https://doi.org/10.1097/AOG.0000000000004377
American College of Obstetricians and Gynecologists. Committee Opinion No. 712: Intrapartum management of intraamniotic infection. Obstet Gynecol. 2017;130(2):e95-e101. PMID 28742677. https://doi.org/10.1097/AOG.0000000000002236
Jain VG, Willis KA, Jobe A, et al. Chorioamnionitis and neonatal outcomes. Pediatr Res. 2022;91(2):289-296 (published online July 1, 2021). PMID 34211129. https://doi.org/10.1038/s41390-021-01633-0
Fowler JR, Simon LV. Chorioamnionitis. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated September 4, 2023. PMID 30335284. https://pubmed.ncbi.nlm.nih.gov/30335284/
Cleveland Clinic. Chorioamnionitis. Cleveland Clinic. Last updated May 11, 2026. https://my.clevelandclinic.org/health/diseases/12309-chorioamnionitis
Merck Manual. Intraamniotic Infection. Merck Manual Consumer Version. Last updated September 2024. https://www.merckmanuals.com/home/women-s-health-issues/complications-of-labor-and-delivery/intraamniotic-infection
Medical disclaimer
The information provided in this article is for educational purposes only and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.
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