Chorioamnionitis

Chorioamnionitis is an infection of the placenta and amniotic fluid that occurs during pregnancy or labor. It represents one of the most serious complications that can affect both mother and baby during delivery, and it is a leading cause of preterm birth, neonatal infection, and long-term neurological injury. For families navigating a difficult birth experience or seeking to understand a diagnosis made during labor, learning about chorioamnionitis can provide clarity about what happened, why certain medical decisions were made, and what to watch for in the days and months following delivery.

This page explains what chorioamnionitis is, how it develops, how it is diagnosed and treated, and what it may mean for the health of both mother and child.

What is Chorioamnionitis?

Chorioamnionitis is an inflammatory condition involving the chorion and amnion, the membranes that surround the baby in the womb, as well as the amniotic fluid and placenta. In most cases, the inflammation is caused by a bacterial infection that travels upward from the vagina into the uterus. The condition typically develops during labor or shortly before delivery, though it can also occur earlier in pregnancy, particularly in cases of preterm labor.

Chorioamnionitis is sometimes referred to as intra-amniotic infection or intra-amniotic inflammation. It is the most common infection-related complication managed in labor and delivery units and is closely associated with maternal fever, fetal distress, and an increased risk of serious newborn complications including sepsis and brain injury.

The condition affects approximately 9.7 per 1,000 live births in the United States. Among term pregnancies, chorioamnionitis complicates about 2 to 6 percent of deliveries. In preterm births, the rate is significantly higher, ranging from 12 to 52 percent depending on how the condition is diagnosed. Extremely premature infants are especially vulnerable. Studies show that up to 94 percent of placentas from extremely preterm births display signs of inflammation, compared to only 3 to 5 percent of term placentas.

How Chorioamnionitis Develops

Most cases of chorioamnionitis result from bacteria that normally live in the vagina ascending into the uterus. Once the membranes rupture, or if labor is prolonged, these bacteria can enter the amniotic sac and cause infection. The longer the membranes remain ruptured before delivery, the greater the risk of infection.

Common bacteria involved in chorioamnionitis include:

• Group B Streptococcus
• Escherichia coli (E. coli)
• Ureaplasma species
• Mycoplasma species
• Gardnerella vaginalis
• Occasionally, fungi such as Candida

Up to 70 percent of chorioamnionitis cases are polymicrobial, meaning that more than one type of bacteria is involved. This makes treatment more complex and underscores the importance of broad-spectrum antibiotics during labor.

Risk Factors

Certain conditions and circumstances increase the likelihood of developing chorioamnionitis. While some of these factors are unavoidable, understanding them can help families and clinicians take steps to minimize risk.

Risk factors include:

• Prolonged rupture of membranes, especially beyond 18 to 24 hours
• Long or difficult labor
• Multiple vaginal examinations during labor
• First-time mothers (nulliparity)
• Use of internal fetal monitoring devices
• Presence of sexually transmitted infections
• Bacterial vaginosis or group B Streptococcus colonization
• Use of epidural anesthesia
• Tobacco or alcohol use during pregnancy
• Young maternal age

It is important to note that chorioamnionitis can occur even in the absence of these risk factors. Many cases happen unexpectedly, and the presence of one or more risk factors does not mean infection is inevitable.

Signs and Symptoms

Chorioamnionitis is typically diagnosed during labor based on clinical findings. The hallmark sign is maternal fever, which signals that the body is responding to infection. However, fever alone is not sufficient for diagnosis.

According to established clinical criteria, a diagnosis of chorioamnionitis requires maternal fever of at least 100.4°F (37.8°C) along with two or more of the following signs:

• Maternal tachycardia, or rapid heart rate (more than 100 beats per minute)
• Fetal tachycardia (more than 160 beats per minute)
• Uterine tenderness
• Foul-smelling or cloudy amniotic fluid
• Elevated maternal white blood cell count (more than 15,000 cells per cubic millimeter)

Some mothers may not experience noticeable symptoms, particularly in early or mild cases. Fetal heart rate changes picked up on monitoring may be the first indication that something is wrong.

Diagnosis

Diagnosis of chorioamnionitis is primarily clinical, based on the symptoms described above. When the diagnosis is uncertain or when more information is needed, additional testing may be performed.

Tests that can support or confirm the diagnosis include:

• Complete blood count to assess white blood cell levels
• C-reactive protein, a marker of inflammation
• Gram stain and culture of amniotic fluid
• Molecular testing to identify specific bacteria
• Placental pathology after delivery

In some cases, particularly after preterm delivery, the diagnosis is made histologically, meaning that a pathologist examines the placenta under a microscope and finds evidence of inflammation or infection. Histologic chorioamnionitis is more common than clinical chorioamnionitis and may be present even when the mother had no symptoms during labor.

Immediate Medical Management

When chorioamnionitis is suspected or confirmed, prompt treatment is essential to protect both mother and baby. The standard approach is to begin intravenous antibiotics as soon as possible, continue them throughout labor, and proceed with delivery in a timely manner.

The recommended antibiotic regimen during labor is:

• Ampicillin plus gentamicin as first-line therapy
• Clindamycin is added if a cesarean section is performed

These antibiotics work together to cover the range of bacteria most likely to be involved in chorioamnionitis. The goal is to reduce the bacterial load in the uterus and amniotic fluid before the baby is delivered, which helps lower the risk of neonatal infection.

Acetaminophen is often given to reduce maternal fever, as high temperatures during labor can increase the baby’s risk of brain injury. In preterm deliveries, corticosteroids may be given to help the baby’s lungs mature, and magnesium sulfate may be used to protect the baby’s brain.

Delivery is typically expedited once chorioamnionitis is diagnosed. Vaginal delivery is preferred when safe, but cesarean section may be necessary depending on the circumstances.

Neonatal Evaluation and Treatment

All infants born to mothers with chorioamnionitis are closely monitored after birth. Because these babies are at increased risk for infection, they typically undergo a sepsis evaluation shortly after delivery.

This evaluation usually includes:

• Blood culture
• Complete blood count
• C-reactive protein
• Sometimes a lumbar puncture to check for meningitis, particularly if the baby is premature or showing signs of illness

Newborns who are full-term, appear healthy, and have normal vital signs may be observed closely for 48 to 72 hours while blood cultures are pending. If the cultures remain negative and the baby shows no signs of infection, antibiotics may not be necessary or can be discontinued early.

However, if the baby is premature, unwell, or showing signs of sepsis, empiric antibiotics are started immediately and continued for a full course of treatment, usually 7 to 10 days for sepsis or longer for meningitis.

Short-Term Complications for the Baby

Chorioamnionitis can lead to a range of serious health problems for the newborn, especially when infection is severe or when the baby is born prematurely.

Common early complications include:

• Neonatal sepsis, a bloodstream infection that can be life-threatening
• Pneumonia
• Meningitis, or infection of the membranes around the brain and spinal cord
• Intraventricular hemorrhage, or bleeding in the brain
• Necrotizing enterocolitis, a serious intestinal disease
• Periventricular leukomalacia, or injury to the white matter of the brain
• Retinopathy of prematurity, which can affect vision
• Increased likelihood of needing intensive care

These complications are more common in preterm infants, but full-term babies exposed to chorioamnionitis are also at higher risk compared to unexposed infants.

Long-Term Outcomes and Neurological Effects

One of the most concerning aspects of chorioamnionitis is its association with long-term neurological problems. Inflammation and infection in the womb can affect the developing brain, particularly in preterm infants whose brains are still very immature.

Research has shown that babies exposed to chorioamnionitis are at increased risk for:

• Cerebral palsy
• Cognitive delays
• Developmental impairment
• Learning difficulties
• Behavioral challenges
• Chronic lung disease

The risk is highest in babies born very prematurely. However, even full-term babies exposed to severe or prolonged infection may experience subtle developmental differences that become apparent as they grow.

It is important to remember that not all babies exposed to chorioamnionitis will have long-term problems. Many recover fully and develop normally. However, ongoing monitoring and early intervention services are often recommended to identify and address any issues as early as possible.

Prevention Strategies

While chorioamnionitis cannot always be prevented, certain practices during pregnancy and labor can reduce the risk.

These include:

• Limiting the number of vaginal exams during labor
• Maintaining strict hand hygiene and sterile technique in the delivery room
• Screening for and treating group B Streptococcus and other infections during pregnancy
• Avoiding unnecessary internal fetal monitoring
• Delivering promptly when membranes have been ruptured for an extended period
• Treating bacterial vaginosis and sexually transmitted infections before labor

When rupture of membranes occurs before labor begins, especially in preterm pregnancies, close monitoring and timely intervention are critical to prevent infection from developing or worsening.

Support and Resources in New York

Families affected by chorioamnionitis have access to comprehensive medical and social support throughout New York State. New York City and regional hospitals follow established guidelines from the American College of Obstetricians and Gynecologists for the diagnosis and management of this condition, and many have specialized perinatal infection and neonatal intensive care teams.

Major medical centers including Mount Sinai, NYU Langone, Columbia Presbyterian, and Albany Medical Center offer high-level obstetric and neonatal care, infectious disease consultation, and follow-up services for infants with complications related to chorioamnionitis.

The New York State Department of Health and New York City Department of Health provide resources for maternal and child health, including early intervention programs for infants at risk of developmental delays. Social workers, lactation consultants, and public health nurses can connect families with services such as home visiting, developmental screening, and financial assistance.

NYBirthInjury.com exists to provide trusted, accurate information to families navigating the complexities of birth-related medical conditions. Whether you are trying to understand a recent diagnosis, seeking clarity about your child’s care, or looking for resources and support, we are here to help guide you through each step.

Ongoing Research and Advances

Medical researchers continue to study chorioamnionitis to improve diagnosis, treatment, and outcomes. Current areas of focus include refining diagnostic criteria, improving methods for testing amniotic fluid, identifying biomarkers that predict which babies are at highest risk for complications, and exploring new ways to protect the developing brain from inflammation and injury.

Academic medical centers in New York and across the country are investigating the role of cytokines and other immune signaling molecules in causing brain injury, as well as therapies that might reduce inflammation or promote healing in exposed infants. These efforts hold promise for better prevention and treatment in the years ahead.

Understanding chorioamnionitis is an important step in making sense of a difficult birth experience. While the condition can lead to serious complications, timely recognition and treatment can make a meaningful difference in outcomes for both mothers and babies. Families who have been affected by chorioamnionitis deserve compassionate, accurate information and access to the resources they need to support their child’s health and development.