What Is Chorioamnionitis?

Chorioamnionitis occurs when bacteria infect the organs and membranes surrounding the fetus and amniotic fluid during pregnancy. It’s estimated that chorioamnionitis affects about 1% to 5% of term deliveries and about one-third of preterm deliveries. 

The infection or inflammation affects the placenta (the organ that supplies oxygen and nutrients) and the chorion and amnion (membranes surrounding the baby that act as protective barriers). Chorioamnionitis is often caused by bacteria found in the vagina. Once suspected, it is treated with antibiotics right away.

This article will provide an overview of chorioamnionitis, including the symptoms, causes, and treatment options. 

Symptoms of Chorioamnionitis 

The symptoms of chorioamnionitis can vary and usually include maternal fever. Other signs include:

• Maternal leukocytosis (high white blood cell count)
• Pelvic pain or soreness
• Increased heart rate (in mother and/or baby)
• Foul-smelling amniotic fluid
• Pus in cervical drainage 

Causes

Chorioamnionitis refers to an infection that leads to inflammation in the placenta, chorion, and amnion. It is often caused by bacteria that are normally found in the vagina. When the bacteria travel into the amniotic sac, an infection can occur. This is more likely to happen when the amniotic sac (bag of waters) breaks for an extended amount of time before delivery.

Risk factors of chorioamnionitis include: 

• Prelabor rupture of membranes (water breaking)
• More than 40 weeks gestation 
• Frequent vaginal exams
• Long labor
• Sexually transmitted infection (STI)
• Internal fetal monitoring 
• Use of alcohol or tobacco
• Group B Streptococcus positive 
• Bacterial vaginosis infection

Diagnosis 

Chorioamnionitis is usually considered any time a pregnant person has a fever. It is important to be evaluated by a healthcare provider as soon as you suspect that you may be ill. The diagnostic process usually starts with a physical exam and thorough history. 

Your healthcare provider may diagnose chorioamnionitis from symptoms alone. Factors used to diagnose chorioamnionitis include maternal fever over 100.4 degrees Fahrenheit at least once and one of two other clinical findings depending on the criteria used.

Classic symptoms of chorioamnionitis used for diagnosis include:

• Maternal tachycardia (rapid heart rate)
• Fetal tachycardia 
• Maternal leukocytosis (high white blood cell count)
• Uterine tenderness
• Foul-smelling amniotic fluid 

Amniocentesis is a procedure that can diagnose chorioamnionitis but is not usually used because of the known risks to the baby. It involves using a needle to remove a small amount of amniotic fluid for testing. 

Treatment 

The treatment for chorioamnionitis depends on several factors, including the symptoms, maternal age and health, and the severity of the infection. Antibiotics are started right away and may continue after birth as well. 

Starting antibiotics early decreases the risk of serious illness in the baby. Risks include neonatal bacteremia (bacteria in the bloodstream), pneumonia, sepsis, and death. Treatment with antibiotics also lowers the risk of maternal complications and length of hospital stay. 

A combination of aminopenicillin and Gentak (gentamicin) is usually used to treat chorioamnionitis. When a cesarean delivery (C-section) is required, Cleocin (clindamycin) or Flagyl (metronidazole) is usually added as well. 

Bacteria that are most commonly associated with chorioamnionitis include:

• Ureaplasma (47%)
• Mycoplasma (30%)
• Bacteroides (30%)
• Gardnerella vaginalis (25%)
• Group B strep (15%)
• Gram-negative rods, including Escherichia coli (E.coli) (8%)

Complications 

There are serious complications to both the mother and baby associated with chorioamnionitis. For the pregnant person, chorioamnionitis can lead to:

• Preterm birth (delivering before 37 weeks)
• Labor interventions 
• Blood transfusion
• Uterine atony (failure of the uterus to contract)
• Pelvic abscess 
• Peritonitis
• Hemorrhage
• Postpartum endometritis 
• Sepsis
• Acute respiratory distress syndrome (ARDS)
• Admission to the intensive care unit (ICU)

Possible complications for the baby include:

• Pneumonia
• Meningitis
• Sepsis
• Intraventricular hemorrhage
• Fetal inflammatory response syndrome (FIRS)
• Need for mechanical ventilation 

Long-term complications for babies may include:

• Bronchopulmonary dysplasia (lung disease in premature babies)
• Periventricular leukomalacia (brain injury affecting premature infants)
• Cerebral palsy (motor disability in children)

Prevention

Fortunately, there are ways to lower your risk for chorioamnionitis. It is important to limit the number of vaginal exams for pregnant people because a vaginal exam can introduce bacteria into the amniotic sac. 

If a pregnant person’s amniotic sac breaks early before labor has started, antibiotics are sometimes needed to lower the risk of infection. Always call your healthcare provider if you are concerned about any new or ongoing symptoms.

Summary

Chorioamnionitis is an infection and inflammation of the placenta, chorion, and amnion during pregnancy. This condition is not common but serious. Possible symptoms include maternal fever, maternal or fetal tachycardia, pelvic soreness, cervical drainage, and foul-smelling amniotic fluid. Chorioamnionitis needs to be treated with antibiotics right away.

Possible complications to the mother include preterm birth, labor interventions, postpartum uterine atony, hemorrhage, endometritis, peritonitis, and sepsis. Possible risks to the baby include respiratory distress syndrome, pneumonia, meningitis, sepsis, and death. In very severe cases, especially if treatment is not implemented appropriately it can lead to death of mother or baby.

A Word From Verywell

Chorioamnionitis is a serious infection, and it is frightening to learn that you may have it. It’s important to remember that early treatment with antibiotics effectively lowers the risk of complications. Any time you have a fever during pregnancy, talk with your healthcare provider to determine if you should be evaluated.