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Explaining premature birth

If your baby is born early - also called 'premature' or 'preterm' - he may need special care.

The definition of a 'premature' or 'preterm' baby is one that is born before 37 weeks. There are different levels of prematurity and these carry their own risks. Very premature babies, born before week 26, are at most risk and are sometimes known as micro preemies. A baby born at 37 weeks or more is known as a 'term' baby. Generally the earlier your baby is born the higher the risk of health problems.

Find out more about reducing the risk factors of premature birth

Causes of premature birth

We still have a lot to learn about premature birth so it's not always possible to explain the causes and why it happens. Factors such as infection can result in prematurely born babies but it is often more complicated than one single reason. This is partly why prevention of premature birth is still in need of extensive research - without knowing the causes, a treatment is difficult.  

Many mothers of premature babies told us they suffer from feelings of terrible guilt, wondering what they did wrong and if they are to blame. The truth is that in the vast majority of cases there is nothing you could have done to prevent premature birth. 

The pages listed below tell you more about the specific known causes of premature birth.


In our statistics section you can read more statistics about prematurity.

In our research section you can learn more about the research we carry out into preterm birth and its prevention.

Reviewed June 2014, next review June 2017


World Health Organisation, Preterm birth fact sheet, Geneva WHO, 2012 (

Norman JE, Greer IA (2011) Preterm labour: managing risk in clinical practice, Cambridge University Press 

BAPM (2008) Management of acute in-utero transfers: a framework for practice. London, British Association of Perinatal Medicine


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