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Updated May 13, 2014

What Chorioamnionitis Is:

Chorioamnionitis is the medical term for a bacterial infection of the uterus and pregnancy membranes during pregnancy. When not detected and treated, chorioamnionitis can lead to serious complications for the mother and baby.

Causes and Risk Factors:

The cause of chorioamnionitis is bacteria having breached the normal defenses of the uterus, usually ascending from lower in the vagina. Common culprits might be group B strep or E. coli bacteria. The condition is most likely to occur when delivery is prolonged after the membranes have been ruptured, and occurrence is most common in preterm births.


When the infection occurs during delivery, signs of chorioamnionitis may include fever, elevated heart rate in the mother and/or baby, pain in the uterus, and an abnormal smell to the amniotic fluid. When chorioamnionitis occurs during pregnancy, there may be no symptoms.


If a doctor suspects chorioamnionitis at a point in pregnancy before the onset of labor, chorioamnionitis may be diagnosed via amniocentesis and testing of the amniotic fluid for signs of bacteria. If the condition is suspected during labor, the doctor may make a diagnosis and opt for treatment based on clinical symptoms.


Treatment of uterine infections will depend on the individual circumstances, but usually the treatment will involve antibiotics. Immediate delivery of the baby may also be needed in some cases.

Complications of Chorioamnionitis:

The consequences of chorioamnionitis are varied. In the best cases, when the infection is detected and treated in a timely manner, there may be no long-term complications for the mother or baby lasting beyond delivery. Doctors will monitor the baby for signs of a resulting infection, but according to the March of Dimes, about 95% to 97% of babies infected with group B strep (one of the bacteria strains found in chorioamnionitis) recover with help from antibiotics. Premature babies are more vulnerable to developing serious complications or dying due to infections.

In some cases, especially when chorioamnionitis occurs earlier in pregnancy and is asymptomatic, it's possible that the condition can be a cause of premature labor or even stillbirth. Research suggests that chorioamnionitis is a common factor in unexplained stillbirths, and there is some evidence that the condition itself might be the cause of the stillbirth in these cases. Unfortunately, not much is known at this point on who might be at risk for early asymptomatic infections and whether there might be a way to diagnose and treat such infections, but future research will hopefully shed more light on this subject.


Chorioamnionitis. University of Virginia Health System. Accessed: Feb 3 2010. http://www.healthsystem.virginia.edu/UVAHealth/peds_hrpregnant/chorioam.cfm

Group B Strep Infection. March of Dimes. Accessed Feb 3 2010. http://www.marchofdimes.com/professionals/14332_1205.asp

Holzman, Claudia, Ximin Lin, Patricia Senagore and Hwan Chun. "Histologic Chorioamnionitis and Preterm Delivery." American Journal of Epidemiology 2007 166(7):786-79.

Lahra MM, Gordon A, Jeffery HE. "Chorioamnionitis and fetal response in stillbirth." Am J Obstet Gynecol. 2007 Mar;196(3):229.e1-4.

Moyo SR, Hägerstrand I, Nyström L, Tswana SA, Blomberg J, Bergström S, Ljungh A. "Stillbirths and intrauterine infection, histologic chorioamnionitis and microbiological findings." Int J Gynaecol Obstet. 1996 Aug;54(2):115-23.

Tolockiene E, Morsing E, Holst E, Herbst A, Ljungh A, Svenningsen N, Hägerstrand I, Nyström L. "Intrauterine infection may be a major cause of stillbirth in Sweden." Acta Obstet Gynecol Scand. 2001 Jun;80(6):511-8.

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