Last updated September 2011. Planned review date: September 2013

Infection and premature birth

Infections can trigger premature birth so it's important to seek medical advice promptly if you're worried.

How do infections cause premature birth?

Research suggests that infections are at least partly to blame for one third of premature births, particularly for women who go into labour before 30 weeks.

Infections may be caused by natural bacteria that are often harmless but have migrated to parts of the body where they shouldn't be, such as the womb.

Types of infection

Intrauterine infections (infections within the womb)

 These are caused by bacteria, and may be responsible for up to 40 percent of premature births.

Genital tract infections

These include bacterial vaginosis, chlamydia, trichomona, gonorrhoea, syphilis and HIV (but not thrush) and have been associated with waters breaking early and premature labour.  

Urinary tract infections (UTIs)

 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.

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Chorioamnionitis

This is an infection of the membranes of the sac that holds your baby and the fluid inside, and usually occurs when an undetected infection progresses up into the womb. If your waters break early (also known as preterm premature rupture of the membranes, or PPROM for short) you are much more susceptible to infection, as the sac is no longer sealed. Chorioamnionitis may trigger premature labour, or you may need to be induced immediately as the infection may spread to your baby, making you both very ill.

Look out for these symptoms of chorioamnionitis:

• high temperature
• a foul-smelling vaginal discharge
• a fast heart rate in your or your baby
• 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.

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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.

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In this section

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Explaining premature birth:

• Your pregnancy history and premature birth
• Infection and premature birth
• Pre-eclampsia and premature birth
• Gestational diabetes and premature birth
• Waters breaking early (PPROM) and premature birth
• Problems with the placenta and premature birth
• Problems with the cervix and premature birth
• Problems with the womb and premature birth
• Multiple pregnancies and premature birth
• Problems with your baby's development and premature birth
• Other medical conditions and premature birth
• Lifestyle factors and premature birth
• Frequently asked questions

Your premature baby:

• Finding out the gestational age
• Gestational age and medical needs

You can also read about

• Reducing the risk of premature birth
• Giving birth to your baby
• Your baby's time in hospital
• Taking your baby home
• Looking after yourself

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Sources

Henderson D, Macdonald S (2004) Mayes Midwifery (13^th edition), London, Balliere Tindall

BMJ Evidence Centre (2011, accessed Sept 2011) Premature newborn care, Diagnosis, History and examination, British Medical Journal http://bestpractice.bmj.com/best-practice/monograph/671/diagnosis/history-and-examination.html

RCOG (2008) When your waters break early (preterm prelabour rupture of membranes) - information for you, Royal College of Obstetricians and Gynaecologists

Locksmith G, Duff P (2011) Infection, antibiotics, and preterm delivery, Seminars in Perinatology, Vol 25, p295-309

Mazor-Dray E, Levy A, Schlaeffer F, Sheiner E (2009) Maternal urinary tract infection: is it independently associated with adverse pregnancy outcome?, 'Journal of Maternal-Fetal Neonatal Medicine', Vol 22, No 2, p124-8

Rennie JA (2005) Roberton’s Textbook of Neonatology (4^th edition), London, Churchill Livingstone

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