What Is Amnionitis?

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Amnionitis, also known as chorioamnionitis, is a serious, intra-amniotic bacterial infection that can occur in pregnant people. In amnionitis, the uterus and the amniotic sac are affected, leading to potential infection of the foetus. This article will be looking at the symptoms of amnionitis while also exploring how it is diagnosed, how it can be prevented and the treatment options available.1 


The amniotic sac is a thin wall that encases the foetus within the uterus during pregnancy. The sac is filled with amniotic fluid and a membrane that covers the foetus. These structures protect the foetus from harm and help regulate the environment of the womb, such as maintaining an appropriate temperature. During pregnancy the uterus is normally a sterile environment; it does not contain any viruses or bacteria. However, certain situations can make it more susceptible to infections.1,2 

Bacteria entering and invading the uterus can cause amnionitis. Bacteria can enter the body through the vagina and the cervix. Sometimes, the bacteria reaches the uterus through the maternal bloodstream. In most healthy women, different populations of commensal bacteria are present in the cervix and the vagina at all times. However, in some individuals, such as those who are immunodeficient, the presence of bacteria can result in infections. Infection of the uterus can lead to multiple complications that are difficult to manage without first delivering the baby. This can result in in preterm births where the baby is born earlier than the expected due date (premature).2 E. coli and Group B Strep are most commonly responsible for amnionitis.

Although amnionitis is more common in people who go into preterm labour, it can also occur during normal labour.  Factors that can increase the risk of amnionitis are: 2 

Symptoms of amnionitis 

There are a variety of symptoms that may present in someone with amnionitis. Usually, a person going into preterm labour can also be indicative of an infection. Signs include experiencing regular uterine contractions and having a dilated cervix.3 

In addition to pre-term labour, additional symptoms can be observed: 

  • Fever
  • Increased heart rate in the mother and in the foetus
  • Cervical discharge 
  • Abdominal pain 
  • Flu-like symptoms 

Diagnosis of amnionitis 

Clinical amnionitis is most notably characterised by maternal fever, high white blood cell count and the presence of amniotic fluid with a foul odour leaking from the cervix. Diagnosis of amnionitis should be based on clinical findings and patient observation.4 

To confirm intra-amniotic infection, several clinical tests can be carried out. These include:5

  • Blood and urine samples test - To determine the white blood cell level 
  • Vaginal cultures - To determine the presence of bacteria and the species
  • Sample of amniotic fluid - To look for the presence of bacteria 
  • Ultrasound- To check the health of the foetus

Treatment of amnionitis

The affected person should be given antibiotics as soon as a diagnosis is made. Ampicillin and gentamicin are the usual first-line antibiotics that are used and both of these drugs are normally administered intravenously. Clindamycin may also be recommended if the infection is particularly severe. Treatment with antibiotics can help to lower the risk of both maternal and foetal complications. 

If signs of infection are identified during active labour, every effort should be made to deliver the baby as quickly and as safely as possible. Certain drugs, such as oxytocin, may be administered to increase contractions and help speed up labour. Although a swift and safe delivery is recommended, a c-section is not typically performed if amnionitis is the only suspected complication. 

In addition to active treatment, several supportive therapies can be done to facilitate labour. Room cooling and eating ice chips have been shown to reduce the mother’s body temperature and subsequently, provide some relief.6,7 

Complications of amnionitis 

There are many complications that can arise from amnionitis. The highest risk of an intra-amniotic infection is preterm labour and preterm premature rupture of the membranes (PPROM).  These are serious complications as they can allow the bacteria to enter the uterus, causing serious maternal and neonatal infections. Infection that has spread to the foetus can result in increased foetal heart rate and white blood cell count, with the risk of mortality also rising.  

In addition to harming the foetus, the mother has a high chance of developing very serious complications. If there is an infection present, it can spread to the bloodstream and cause sepsis, in both the mother and the foetus. Sepsis is very serious as it can dramatically lower blood pressure which can lead to organ damage. Additionally, toxins from bacteria can also be released into the body causing harm. This is why immediate action is imperative to effectively treat amnionitis.7,8

Prevention of amnionitis 

Having limited vaginal examinations can also lower the likelihood of developing amnionitis. If you are in a situation where your water has broken early or you are in preterm labour, the healthcare provider might administer antibiotics intravenously as it is the best method to prevent infection.9 It is advisable to discuss any pregnancy concerns with your healthcare provider for the best health outcome possible. 


Amnionitis is a serious bacterial infection that can affect any pregnant individual. It occurs due to the early rupture of the uterine membranes. The signs and symptoms such as observation of a foul-smelling amniotic fluid, maternal fever and a high white blood cell count in the mother and foetus can present during the infection. Clinical testing can be used to diagnose amnionitis. Immediate treatment with intravenous antibiotics is essential to prevent the spread of bacteria in the mother and foetus. Major complications of amnionitis include neonatal mortality as well as maternal and neonatal sepsis. If you are at risk of developing amnionitis, antibiotics can be given as a front-line preventive measure. Preventative measures and treatment plans administered in a timely manner can effectively tackle this life-threatening infection and avoid major health complications for the mother and baby. 


  1. Amnionitis - an overview | ScienceDirect Topics [Internet]. [cited 2023 Mar 16]. Available from: https://www.sciencedirect.com/topics/medicine-and-dentistry/amnionitis
  2. definition & guidelines for data collection, analysis, and presentation of immunization safety data. Vaccine [Internet]. 2019 [cited 2023 Mar 16]; 37(52):7610–22. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6891229/
  3. Czikk MJ, McCarthy FP, Murphy KE. Chorioamnionitis: from pathogenesis to treatment. Clinical Microbiology and Infection [Internet]. 2011 [cited 2023 Mar 16]; 17(9):1304–11. Available from: https://www.sciencedirect.com/science/article/pii/S1198743X14612088 
  4. Tita ATN, Andrews WW. Diagnosis and Management of Clinical Chorioamnionitis. Clin Perinatol [Internet]. 2010 [cited 2023 Mar 16]; 37(2):339–54. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008318/
  5. Fan S-R, Liu P, Yan S-M, Peng J-Y, Liu X-P. Diagnosis and Management of Intraamniotic Infection. Maternal-Fetal Medicine [Internet]. 2020 [cited 2023 Mar 16]; 2(4):223. Available from: https://journals.lww.com/mfm/fulltext/2020/10000/diagnosis_and_management_of_intraamniotic.6.aspx
  6. Intrapartum Management of Intraamniotic Infection [Internet]. [cited 2023 Mar 16]. Available from: https://www.acog.org/en/clinical/clinical-guidance/committee-opinion/articles/2017/08/intrapartum-management-of-intraamniotic-infection
  7. Miao J, Ren Z, Rao Y, Xia X, Wang J, Xu F, et al. Pathological staging of chorioamnionitis contributes to complications in preterm infants. Italian Journal of Pediatrics [Internet]. 2020 [cited 2023 Mar 16]; 46(1):127. Available from: https://doi.org/10.1186/s13052-020-00895-4
  8. Hastings-Tolsma M, Bernard R, Brody MG, Hensley J, Koschoreck K, Patterson E. Chorioamnionitis: Prevention and Management. MCN: The American Journal of Maternal/Child Nursing [Internet]. 2013 [cited 2023 Mar 16]; 38(4):206. Available from: https://journals.lww.com/mcnjournal/Abstract/2013/07000/Chorioamnionitis__Prevention_and_Management.4.aspx

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Sarah Nadiri

Masters in Cancer, MSc University College London, London

Sarah is a registered biomedical scientist with a specialty in cancer research studies. She has five years experience working in various research facilities such as the Cancer Institute and The Francis Crick Institute. Additionally she has experience working in clinics, in various hospital labs around London and various intermediary care roles within the NHS. She joined Klarity in February and is currently contributing as a medical writer.

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