Premature birth statistics

A preterm birth, one that happens before 37 completed weeks of pregnancy, is the number one cause of newborn deaths and the second leading cause of deaths in children under five.

premature birth infographic

Preterm birth, which occurs before 37 completed weeks of pregnancy, is the biggest cause of newborn deaths and the second biggest cause of deaths in children under five.

Preterm babies are at increased risk of illness, disability and death. The World Health Organisation gives the following definitions for the different stages of preterm birth:

  • extremely preterm: before 28 weeks
  • very preterm: from 28 to 32 weeks
  • moderate to late preterm: from 32 to 37 weeks.

In the UK, around 60,000 babies are born prematurely each year. Globally, more than 1 in 10 pregnancies will end in preterm birth (and this number is rising). 

In babies born preterm, the chance of survival at less than 22 weeks is close to zero, while at 23 weeks it is 19%, at 24 weeks 40%, at 25 weeks about 66% and at 26 weeks 77%. In  2015, there were over 850 deaths of babies born at 22 and 23 weeks.

The length of gestation typically reduces with each additional baby. On average, most singleton pregnancies last 39 weeks, twin pregnancies 36 weeks, triplets 32 weeks, quadruplets 30 weeks and quintuplets 29 weeks. Almost 60% of twins are born preterm, while 90% of triplets are preterm.

Premature birth is the biggest global killer of young children, with more than 1 million children dying each year due to the complications of preterm birth, mostly in the developing world.

Causes of preterm birth

In many cases the reason for the premature birth is unknown. The reasons below can overlap.

  • 25% of preterm births are planned because the mother and/or baby are suffering life-threatening complications such as pre-eclampsia, kidney disease or growth restriction.
  • 40% are linked to waters breaking early (premature rupture of the membranes).
  • 25% are linked to an emergency event, for example, placental abruption (when the placenta detaches itself from the uterus), infection, eclampsia or prolapsed cord (when the umbilical cord exits the body before the baby).
  • In 40% of cases the cause is not known.

Survival rates and long-term outcomes of preterm birth

  • In England, survival rates of very premature babies increased from 53% in 2006 to 80% in 2011.
  • Survival increases for each week the baby stays in the womb. Those born alive at 27 weeks have an 87 per cent chance of surviving, at 28 weeks it is 92 per cent and at 29 weeks, 95 per cent.
  • A study following the progress of very premature babies (born before 27 weeks) in the UK and Republic of Ireland found a high level of disability once the children reached 6 years of age.
  • When children born before 26 weeks were reassessed in middle childhood (aged 11 years), the researchers found that 45% had serious cognitive impairment.

Read more about our research into premature birth

  • Clinician scanning a pregnant woman

    The London Preterm (premature birth) Surveillance Clinic

    This unique Preterm Surveillance Clinic – funded by Tommy's as part of our research in St Thomas' Hospital, London, has won an NHS Innovation Challenge Prize, for its success in reducing the number of premature births in South East London.

  • researcher looking at samples in the Tommy's London centre

    Our prematurity research centre at St Thomas' Hospital, London

    Tommy’s prematurity research centre in London is based at St Thomas’ Hospital. Opened in 1995, it is the first Maternal and Fetal Research Unit in the UK. It houses 87 clinicians, scientists and postgraduate students and last year published 78 scientific papers in peer-reviewed journals.

Why our work is necessary



  • World Health Organisation (2015) Preterm birth Available at: (accessed 2 February 2016).
  • ONS (2013) Gestation-specific Infant Mortality in England and Wales, 2013. Office of National Statistics, London, England
  • ISD Scotland (2016) Births in Scottish HospitalsInformation Services Division, NHS National Services Scotland.
  • NSRA Northern Ireland (2015) Registrar general annual report. Northern Ireland Statistics and Research Agency, Belfast, Northern Ireland
  • Cloherty JP. Care of the extremely low birth weight infant. Manual of neonatal care (7th edn). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2012.
  • American Pregnancy Association. Complications in a multiples pregnancy. Available at: (accessed 19 February 2016).
  • National Institute for Health and Care Excellence (NICE). Preterm labour and birth. London: NICE, 2013. Available at: (accessed 2 February 2016).
  • Henderson C, Macdonald S. Mayes midwifery: a textbook for midwives. Philadelphia: Bailliere Tindall, 2011.
  • Costeloe KL, Hennessy EM, Haider S, et al. Short-term outcomes after extreme preterm birth in England: comparison of two birth cohorts in 1995 and 2006 (the EPICure studies). BMJ 2012;345:e7976.
  • MBRACE-UK (2017) Perinatal Mortality Surveillance Report Available at: (accessed 28th June 2017)
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