Find out more about your stage of pregnancy

Infection and premature birth

Infection is a frequent cause of premature birth.

Intrauterine infections and premature birth

Intrauterine infection is infection within the womb. Research suggests that intrauterine infection may be responsible for as many as 40 percent of preterm births.

How does intrauterine infection cause premature birth?

The womb, amniotic fluid and the environment in which the baby develops is normally sterile but sometimes micro-organisms find their way into this environment. These are usually natural bacteria, harmless normally, but have migrated to parts of the body where they shouldn't be. The most common cause of intrauterine infection is through the vagina and cervix, but it can also come through the placenta, through the fallopian tubes or via invasive procedures such as amniocentesis.

Infections that could ascend to the womb include E-Coli and Group B Streptococcus (GBS), bacterial vaginosis, chlamydia, trichomona, gonorrhoea, syphilis and HIV (but not thrush).

If the infection reaches the womb it can cause the fetal membranes (membrane of the sac that surrounds your baby in the womb) to become inflamed and infected. This is called chorioamnionitis.

What are the effects of chorioamnionitis?

This is an infection of the membranes of the sac that holds your baby and the waters, and usually occurs when an undetected infection progresses up into the womb. The infection causes the membranes to become inflamed and this may in itself trigger preterm contractions. It could also cause the waters to break early (also known as preterm premature rupture of the membranes, or PPROM for short). When an infection causes PPROM the waters are no longer sterile. Your baby may need to be born soon to prevent a more serious infection.

Look out for these symptoms of chorioamnionitis:

  • high temperature
  • a foul-smelling vaginal discharge
  • fast pulse rate
  • pain in your abdomen.

If you have any of these symptoms, seek advice from your healthcare team as soon as possible as you may need treatment.

Read more about waters breaking early/preterm premature rupture of the membranes (PPROM)

Urinary tract infections (UTIs) and premature birth

Often caused by the E-Coli bug, UTIs affect about five percent of pregnant women. In between one third and a half of those women, the UTI will travel up into the kidneys, causing acute pyelonephritis, a kidney infection that can cause premature labour and low birthweight. Watch out for these symptoms of UTIs:

  • high fever
  • nausea
  • vomiting
  • pain in your sides or lower back
  • discomfort or pain when passing urine.

If you have any of these symptoms, contact your healthcare team as soon as possible as you may need antibiotics.

Treatment for infections

It is not always easy to spot an infection; in the early stages there may be no obvious symptoms. If there is any indication of an infection, for example if you are running a fever, your healthcare team will test you with either a blood test or a simple swab.

If your waters break early, you may be given antibiotics as a matter of course, to reduce the risk of chorioamnionitis. If the infection has progressed beyond a certain point, your baby may need to be delivered, as antibiotics may be less effective. In most cases of chorioamnionitis, taking antibiotics does not reduce the risk of premature birth. For this reason, there is no screening and treatment for bacterial vaginosis and vaginal infections.

We value your feedback! Every month we will choose one person at random who feeds back to WIN a high street voucher!
Questions that require an answer are marked with  *
* Was this page helpful?
* Please tell us more...
* Email address

The causes and problems of premature birth

Your premature baby:

You can also read about

Reviewed June 2014, next review June 2017


J David, Steer P et al (2010) High risk pregnancy, management options, Elsevier Saunders

BMJ Best Practice (accessed March 2014)

Sangkomkamhang US, Lumbiganon P, Prasertcharoensook W, Laopaiboon M (2009) Antenatal lower genital tract infection screening and treatment programs for preventing preterm delivery, The Cochrane Collaboration, Wiley

RCOG (2011) When your waters break early (preterm prelabour rupture of membranes) – information for you, Royal College of Obstetricians

Rennie JM (2012), Rennie and Robertons Textbook of Neonatology, Fifth edition. Elsevier.

Copyright © Tommy's. TOMMY'S is registered charity no 1060508 and SCO39280