Chorioamnionitis, also referred to as amnionitis and intra-amniotic infection, is an infectious condition occurring during pregnancy, characterized by irritation and inflammation of the amnion and chorion (fetal membranes) as well as the amniotic fluid . It is more common during the second and third trimesters, but can also occur during the first trimester. The infection may lead to life threatening complications unless treated at an early stage.
Group B streptococci, E. coli and various anaerobic bacteria are usually responsible for this infection . Premature rupture of membranes (PROM) is one of the principal risk factors of intra-amniotic infection. However, it can also occur in women with intact amniotic membrane, especially during prolonged labor when the uterus and the vagina remain exposed to each other . The bacteria in the vaginal area travel through the cervix to the fetal membranes and then into the amniotic sac and fluid, leading to abnormal symptoms.
The following risk factors may also lead to infection:
The above symptoms are considered as the diagnostic criteria for chorioamnionitis. Doctors suspect the infection if the mother experiences the symptoms of fever, increased heart rate and unusual vaginal discharge, especially during the later stages of pregnancy. A thorough physical examination (for signs like uterine tenderness) is necessary for confirming the diagnosis  while the doctor may also examine the medical history of the patient.
No additional diagnostic tests may be necessary if the affected woman has already reached full term. But, a fetal ultrasound may be performed for assessing the fetal health . The baby is also examined for signs of infection after delivery.
In case of patients in preterm labor, blood tests and amniocentesis  may be performed to check for bacteria. Low glucose levels along with the presence of bacteria in the amniotic fluid sample collected from the patient help to confirm the diagnosis.
Certain non-infectious conditions and extrauterine infections can lead to symptoms similar to chorioamnionitis:
The treatment depends on the severity of the condition, the patient’s medical history and the pregnancy trimester. 
Antibiotic medications consisting of gentamicin, amoxicillin and metronidazole  may be prescribed to the mother for fighting the infection before delivery. The medicines are generally administered intravenously (IV administration). Antibiotic treatment may also be necessary for the newborn baby to terminate the bacteria responsible for the infection .
Immediate delivery of the baby is the best treatment option for full term pregnant women with chorioamnionitis. Pre-term delivery is also common in case of severe infection. Oxytocin may be recommended for inducing labor if the condition leads to uterine atony (loss of uterine muscle tone) . Doctors may recommend a c-section delivery if:
The outcome may vary depending on the severity of the infection and the time of diagnosis. Women who get the infection later in pregnancy are less at risk of developing life-threatening complications than those affected by the infection during early pregnancy. Long term adverse effects are very rare. Those with a history of chorioamnionitis in their first pregnancy have a higher risk of recurrence in the next one .
Severe cases of the infection are often accompanied by conditions like funisitis (an inflammation of the
connective tissues of the umbilical cord) and vasculitis (affecting the umbilical blood vessels because of
the inflammatory cells of the fetus).
Statistics show it to occur in around 2% of births in United States. It is also considered to be one of the main reasons for premature delivery in the country.
ICD 9 code for chorioamnionitis is 658.4 . When chorioamnionitis affects the fetus or newborn, the code 762.7 is used.
ICD-10 code for chorioamnionitis is O41.1 . The ICD-10 code P02.7 is used when chorioamnionitis affects the fetus or newborn.