Mild acute chorioamnionitis is a medical condition that can occur during pregnancy, involving inflammation of the fetal membranes. This condition holds importance for both maternal and infant health, making a clear understanding of its characteristics and implications valuable.
What is Mild Acute Chorioamnionitis?
Chorioamnionitis is the inflammation of the fetal membranes, specifically the amnion and chorion, which are the sacs surrounding the developing fetus. It is frequently linked to a bacterial infection and is also known as intra-amniotic infection (IAI) or “triple I” (intrauterine infection or inflammation, or both). It can develop before, during, or after labor.
The primary cause of chorioamnionitis is a bacterial infection that ascends from the vagina into the uterus. Common bacteria include Escherichia coli, Group B Streptococcus, and various anaerobic bacteria. Other microorganisms like Ureaplasma, Mycoplasma hominis, and certain sexually transmitted infections such as chlamydia and gonorrhea can also contribute.
Several factors increase the likelihood of developing chorioamnionitis. These include premature labor, prolonged rupture of membranes (PROM), where the amniotic sac breaks long before delivery, and a long duration of labor. Frequent vaginal examinations during labor, especially after membranes have ruptured, can also heighten the risk by potentially introducing bacteria into the uterus. Other contributing factors include a first pregnancy, young maternal age (under 21), low socioeconomic status, and pre-existing vaginal infections like bacterial vaginosis.
Individuals with chorioamnionitis may experience a range of symptoms. Common signs include maternal fever, often above 38.0°C (100.4°F), and a rapid maternal heartbeat. The uterus may also feel tender or painful upon examination. Changes in vaginal discharge, such as a foul odor or unusual discoloration of the amniotic fluid, can also indicate infection.
Diagnosing and Classifying the Condition
Healthcare providers diagnose chorioamnionitis based on clinical criteria and laboratory findings. A suspected diagnosis involves maternal fever coupled with at least one additional sign. These signs include maternal leukocytosis (an elevated white blood cell count, typically above 15,000 cells/mm³), fetal tachycardia (a fetal heart rate exceeding 160 beats per minute), uterine tenderness, or purulent or foul-smelling amniotic fluid.
While clinical signs guide initial suspicion, a definitive diagnosis involves a histological examination of the placenta and membranes after birth. This involves microscopic analysis of tissue samples, confirming inflammatory cells. Amniocentesis, a procedure to collect amniotic fluid for testing, may also be performed, especially in cases of preterm labor. Analysis of the amniotic fluid might reveal bacteria, a low glucose concentration, or a high white blood cell count.
The distinction between “mild” and more severe forms of chorioamnionitis is primarily made through histological examination, which assesses inflammation. Mild or early-stage chorioamnionitis is characterized by the infiltration of maternal neutrophils, a type of immune cell, into the chorion, chorionic plate, or amnion. In more severe cases, microabscesses, small collections of neutrophils, may be present, often between the chorion and decidua. Even when mild, the condition requires prompt medical attention due to its potential to progress and impact maternal and fetal well-being.
Management and Potential Outcomes
Immediate treatment for mild acute chorioamnionitis involves broad-spectrum antibiotics for the mother to combat the bacterial infection. Common antibiotic regimens include a combination of ampicillin and gentamicin, often initiated during labor. If a cesarean delivery is performed, clindamycin may be added.
Delivery of the baby is considered the definitive treatment for chorioamnionitis, as it resolves the source of infection. Labor may be induced or augmented if not already in progress, and vaginal delivery is preferred unless there are other obstetric indications for a cesarean section. Antibiotic therapy can help improve fetal signs of infection and minimize maternal complications, allowing for a trial of labor.
If left untreated or if the condition progresses, chorioamnionitis can lead to complications for both the mother and the neonate. For the mother, risks include postpartum hemorrhage, where the uterus does not contract adequately after delivery, and endometritis, an infection of the uterine lining. More serious maternal complications, though rare with prompt treatment, include sepsis, a life-threatening bloodstream infection, or localized pelvic infections.
Neonates exposed to chorioamnionitis face risks such as early-onset neonatal sepsis, pneumonia, and respiratory distress syndrome, particularly if born prematurely. There is also an increased risk of long-term neurological complications, including cerebral palsy, especially if the infection contributes to preterm birth. While antibiotics significantly reduce the incidence and severity of infection for both mother and baby, close monitoring and timely intervention remain important.