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Chorioamnionitis is a bacterial infection present in the outer (chorion) and inner (amnion) membranes that surrounds the baby, the placenta, or in the amniotic fluid that happens before or during labor. In this blog post, we will discuss the causes, symptoms, treatment, and outlook for pregnancies affected by chorioamnionitis.

Causes of Chorioamnionitis

Chorioamnionitis, which is also called intraamniotic infection or amnionitis, is usually caused by a bacterial infection that starts in the vagina, rectum, or anus and then moves into the uterus or womb. The bacteria that most commonly cause this condition are E. coli and Group B strep, which are both bacteria that can be present in your system normally and only sometimes cause problems.

Certain groups of people are more likely than others to get chorioamnionitis. If you are younger than 21 years old, of lower socioeconomic status, or this is your first pregnancy, you are more likely to develop this condition. Other things that can increase the risk of getting this type of infection during pregnancy and labor are: if your water breaks more than 12-18 hours before baby is born, if you are in active labor more than 12 hours, and if you have multiple vaginal examinations after your water has broken or internal fetal monitoring during labor. Chorioamnionitis can also cause and is more likely to occur during preterm birth, which is when labor begins before week 37 of pregnancy, especially if labor begins with your bag of waters breaking.

Most people with chorioamnionitis who receive antibiotics—often ampicillin, penicillin, or erythromycin—recover fully and see no long term effects on their life or subsequent fertility.

Symptoms and Treatment of Chorioamnionitis

Sometimes chorioamnionitis is asymptomatic, meaning it does not cause symptoms, but if symptoms are present, they might include:

Your doctor or midwife will diagnose you based on the presence of symptoms and a physical exam. They might also check for bacteria in your blood and in the amniotic fluid. Once you have been diagnosed, your care team will likely treat you with intravenous antibiotics—medicine that you receive via your bloodstream—and by delivering your baby, though chorioamnionitis alone is not usually considered by physicians to be a reason for your baby to be born by cesarean section instead of vaginally. 

Most people with chorioamnionitis who receive antibiotics—often ampicillin, penicillin, or erythromycin—recover fully and see no long term effects on their life or subsequent fertility. There are complications that can arise, however, which include more difficult labor and delivery, blood infections, infections of the uterine lining or abdominal region, and possible blood clots in the lungs.

Likewise, most babies born to mothers with chorioamnionitis are usually healthy, though they may need to be treated with antibiotics if they also contract the infection. In very rare cases, babies whose mothers had this condition during labor might have trouble breathing or develop blood infections or meningitis, which is an infection of the spinal cord and brain.

Preventing Chorioamnionitis

Since the infection usually starts elsewhere and then spreads to the uterus, where it can infect the baby, amniotic fluid, and surrounding membranes, your doctor will likely monitor you closely for signs of bacterial vaginosis, which occurs when there is an overgrowth of bacterial in the vagina and test you for the presence of Group B strep. You can also tell your care provider if you experience vaginal discharge that smells bad, especially if it smells like fish, as this could be a sign of bacterial vaginosis.

If your water breaks before 37 weeks of pregnancy—a condition known as premature rupture of membranes—you are highly likely to develop chorioamnionitis. Thus, your care provider will likely give you antibiotics, probably ampicillin and erythromycin, intravenously even if you do not have any signs of infection. This use of antibiotics has been shown to prevent the development of chorioamnionitis and to lead to better outcomes for both mothers and preterm infants.

Abby Olena
Dr. Abby Olena has a PhD in Biological Sciences from Vanderbilt University. She lives with her husband and children in North Carolina, where she writes about science and parenting, produces a conversational podcast, and teaches prenatal yoga.

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