A preterm birth is one that happens before 37 completed weeks of pregnancy.
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 31 weeks
- Moderate to late preterm: from 32 to 37 weeks.
General UK premature birth statistics
- Around 8% of births in the UK are preterm. That is around 60,000 babies each year.
- This is higher than many countries in Europe and higher than Cuba and Iran
Of the births that were preterm in the UK:
- 5% were extremely preterm (before 28 weeks)
- 11% were very preterm (between 28 and 32 weeks)
- 85% were moderately preterm (between 32 and 37 weeks).
In 2019, live births where gestational age was under 24 weeks increased to 0.15% compared with 0.13% in 2018 and 0.11% in 2010.
Chances of survival following preterm birth
Medical advances mean that we are getting better at treating preterm babies but the chances of survival still depend on gestational age (week of pregnancy) at time of birth.
- Less than 22 weeks is close to zero chance of survival
- 22 weeks is around 10%
- 24 weeks is around 60%
- 27 weeks is around 89%
- 31 weeks is around 95%
- 34 weeks is equivalent to a baby born at full term.
Preterm birth and neonatal death
Complications arising from premature birth is the leading cause of neonatal death (death in the first few weeks after birth) in the UK.
Preterm birth and multiple pregnancies
Having more than one baby is a risk factor for preterm birth. On average, most singleton pregnancies last 39 weeks, twin pregnancies 37 weeks and triplets 33 weeks.
- Risk of prematurity with singleton pregnancy: 7%
- Risk of prematurity with multiple pregnancy: 57%
Risk of disability in preterm children
Generally, the earlier the birth, the higher the risk of problems. However these are only statistics and cannot predict how an individual child will do; some extremely premature babies do very well and develop into healthy children.
- 1 in 10 of all premature babies will have a permanent disability such as lung disease, cerebral palsy, blindness or deafness.
- 1 in 2 of premature babies born before 26 weeks of gestation will have some sort of disability (this includes mild disability such as requiring glasses).
In one study of 241 children born before 26 weeks' gestation the following was found:
- 22% severe disability (eg cerebral palsy + not walking, low cognitive scores, blindness, profound deafness)
- 24% moderate disability (eg cerebral palsy + walking, IQ/cognitive scores in the special needs range, lesser degree of visual or hearing impairment)
- 34% mild disability (defined as low IQ/cognitive score, squint, requiring glasses)
- 20% no problems.
Preterm birth by ethnicity
The risk of preterm birth is highest for Black Caribbean women and lowest for White British and White Other.
- Bangladeshi: 8%
- Indian: 7%
- Black African: 8%
- Black Caribbean: 10%
- White British: 7%
- White Other: 6%
Causes of preterm birth
In some cases a cause of preterm birth can be shown but more often it is unknown or unclear.
In 1 in 4 preterm births, the birth is planned (induced labour or c-section) to save the life of mother or baby from pregnancy complications such as pre-eclampsia, fetal growth restriction, waters breaking early (PPROM) or infection
Preventing premature birth
Too often health professionals are not able to tell women why they have had a premature birth. This area of research is underfunded, with many taking an unhelpful (and unique to pregnancy) approach of ‘It was not meant to be’.
Research into why premature birth happens is the only way we can save lives and prevent future loss. Tommy's funds more than £400k of research into premature birth every year. We are focused on predicting early which women will have a premature birth and treating them to prevent it happening.