- extremely preterm (less than 28 weeks)
- very preterm (28 to 32 weeks)
- moderate to late preterm (32 to 37 weeks).
Induction or caesarean birth should not be planned before 39 completed weeks unless medically indicated.
An estimated 15 million babies are born too early every year. That is more than 1 in 10 babies. Approximately 1 million children die each year due to complications of preterm birth (1). Many survivors face a lifetime of disability, including learning disabilities and visual and hearing problems.
Globally, prematurity is the leading cause of death in children under the age of 5 years. And in almost all countries with reliable data, preterm birth rates are increasing.
Inequalities in survival rates around the world are stark. In low-income settings, half of the babies born at or below 32 weeks (2 months early) die due to a lack of feasible, cost-effective care, such as warmth, breastfeeding support, and basic care for infections and breathing difficulties. In high-income countries, almost all of these babies survive. Suboptimal use of technology in middle-income settings is causing an increased burden of disability among preterm babies who survive the neonatal period.
More than three quarters of premature babies can be saved with feasible, cost-effective care, such as essential care during child birth and in the postnatal period for every mother and baby, provision of antenatal steroid injections (given to pregnant women at risk of preterm labour and under set criteria to strengthen the babies’ lungs), kangaroo mother care (the baby is carried by the mother with skin-to-skin contact and frequent breastfeeding) and antibiotics to treat newborn infections. For example, continuity of midwifery-led care in settings where there are effective midwifery services has been shown to reduce the risk of prematurity by around 24%.
Preventing deaths and complications from preterm birth starts with a healthy pregnancy. Quality care before, between and during pregnancies will ensure all women have a positive pregnancy experience. WHO’s antenatal care guidelines include key interventions to help prevent preterm birth, such as counselling on healthy diet and optimal nutrition, and tobacco and substance use; fetal measurements including use of ultrasound to help determine gestational age and detect multiple pregnancies; and a minimum of 8 contacts with health professionals throughout pregnancy to identify and manage other risk factors, such as infections. Better access to contraceptives and increased empowerment could also help reduce preterm births.
Why does preterm birth happen?
Preterm birth occurs for a variety of reasons. Most preterm births happen spontaneously, but some are due to early induction of labour or caesarean birth, whether for medical or non-medical reasons.
Common causes of preterm birth include multiple pregnancies, infections and chronic conditions such as diabetes and high blood pressure; however, often no cause is identified. There could also be a genetic influence. Better understanding of the causes and mechanisms will advance the development of solutions to prevent preterm birth.
Where and when does preterm birth happen?
More than 60% of preterm births occur in Africa and South Asia, but preterm birth is truly a global problem. In the lower-income countries, on average, 12% of babies are born too early compared with 9% in higher-income countries. Within countries, poorer families are at higher risk.
The 10 countries with the greatest number of preterm births(2):
- India: 3 519 100
- China: 1 172 300
- Nigeria: 773 600
- Pakistan: 748 100
- Indonesia: 675 700
- United States of America: 517 400
- Bangladesh: 424 100
- Philippines: 348 900
- Democratic Republic of the Congo: 341 400
- Brazil: 279 300
The 10 countries with the highest rates of preterm birth per 100 live births (2):
- Malawi: 18.1 preterm births per 100 births
- Comoros: 16.7
- Congo: 16.7
- Zimbabwe: 16.6
- Equatorial Guinea: 16.5
- Mozambique: 16.4
- Gabon: 16.3
- Pakistan: 15.8
- Indonesia: 15.5
- Mauritania: 15.4
Of 65 countries with reliable trend data, all but three show an increase in preterm birth rates over the past 20 years. Possible reasons for this include better measurement, increases in maternal age and underlying maternal health problems such as diabetes and high blood pressure, greater use of infertility treatments leading to increased rates of multiple pregnancies, and changes in obstetric practices such as more caesarean births before term.
There is a dramatic difference in survival of premature babies depending on where they are born. For example, more than 90% of extremely preterm babies (less than 28 weeks) born in low-income countries die within the first few days of life; yet less than 10% of extremely preterm babies die in high-income settings.
In 2012, WHO and partners published a report Born too soon: the global action report on preterm birth that included the first-ever estimates of preterm birth by country.
WHO is committed to reducing the health problems and lives lost as a result of preterm birth:
- Working with Member States and partners to implement Every newborn: An action plan to end preventable deaths adopted in May 2014 in the framework of the UN Secretary-General’s Global strategy for women’s and children’s health;
- Working with Member States to strengthen the availability and quality of data on preterm births;
- Providing updated analyses of global preterm birth levels and trends every 3 to 5 years;
- Working with partners around the world to conduct research into the causes of preterm birth, and test effectiveness and delivery approaches for interventions to prevent preterm birth and treat babies that are born preterm;
- Regularly updating clinical guidelines for the management of pregnancy and mothers with preterm labour or at risk of preterm birth, and guidelines on the care of preterm babies, including kangaroo mother care, feeding babies with low birth weight, treating infections and respiratory problems, and home-based follow-up care (see WHO 2015 recommendations on interventions to improve preterm outcomes);
- Developing tools to improve health workers’ skills and assess the quality of care provided to mothers at risk of preterm delivery and preterm babies; and
- Supporting countries to implement WHO's antenatal care guidelines, aimed at reducing the risk of negative pregnancy outcomes, including preterm births, and ensuring a positive pregnancy experience for all women.
Guidelines to improve preterm birth outcomes
WHO has developed new guidelines with recommendations for improving outcomes of preterm births. This set of key interventions can improve the chances of survival and health outcomes for preterm infants. The guidelines include interventions provided to the mother – for example steroid injections before birth, antibiotics when her water breaks before the onset of labour, and magnesium sulfate to prevent future neurological impairment of the child – as well as interventions for the newborn baby – for example thermal care, feeding support, kangaroo mother care, safe oxygen use, and other treatments to help babies breathe more easily.
WHO is currently coordinating two clinical trials, called the WHO ACTION Trials (Antenatal Corticosteroids for Improving Outcomes in preterm Newborns) for women at risk of preterm birth by:
- Immediate kangaroo mother care (KMC) multi-country trial (compared with the current recommendations of initiating KMC when baby is stable) in Ghana, India, Malawi, Nigeria and the United Republic of Tanzania.
- Implementation research to scale-up KMC in India and Ethiopia.
The trials will assess how steroid injections can be used safely and effectively for women and preterm newborns in low- and middle-income countries.
(1) Liu L, Oza S, Hogan D, Chu Y, Perin J, Zhu J, et al. Global, regional, and national causes of under-5 mortality in 2000-15: an updated systematic analysis with implications for the Sustainable Development Goals. Lancet. 2016;388(10063):3027-35.
(2) Blencowe H, Cousens S, Oestergaard M, Chou D, Moller AB, Narwal R, Adler A, Garcia CV, Rohde S, Say L, Lawn JE. National, regional and worldwide estimates of preterm birth. The Lancet, June 2012. 9;379(9832):2162-72. Estimates from 2010.