Preterm is defined as babies born alive before 37 weeks of pregnancy are completed. There are sub-categories of preterm birth, based on gestational age:
- 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.
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.
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.
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 recommendations on interventions to improve preterm birth outcomes
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.
What is a premature baby?
A premature baby is one who is born too early, before 37 weeks of pregnancy. Each year, about 1 in 10 babies in the United States is born prematurely. Premature babies may not be fully developed at birth. They may have more health problems and may need to stay in the hospital longer than babies born later. Thanks to advances in medical care, even babies born very prematurely are more likely to survive today than ever before.
Your baby’s health care provider may use these terms to describe your baby’s birth:
- Late preterm: Your baby is born between 34 and 36 completed weeks of pregnancy.
- Moderately preterm: Your baby is born between 32 and 34 weeks of pregnancy.
- Very preterm: Your baby is born at less than 32 weeks of pregnancy.
- Extremely preterm: Your baby is born at or before 25 weeks of pregnancy.
Some health problems related to premature birth can last a lifetime. Other problems, like intellectual or developmental disabilities, can show up as your baby grows and later in childhood. These are problems with how the brain works that can cause a person to have trouble or delays in physical development, learning, communicating, taking care of himself or getting along with others.
The earlier in pregnancy a baby is born, the more likely he is to have health problems. Babies born before 34 weeks of pregnancy are mostly likely to have health problems, but babies born between 34 and 37 weeks of pregnancy are also at increased risk of having health problems related to premature birth. Some premature babies need to spend time in a hospital’s newborn intensive care unit (also called NICU). This is the nursery in a hospital where sick newborns get medical care. Premature babies stay in the NICU until their organs develop enough to stay alive without medical support. Some babies need NICU care for weeks or months until they can breathe on their own, eat by mouth and maintain their body temperature and body weight.
Do premature babies need special medical care?
Talk to your baby’s health care providers about any health conditions your baby has. He may be healthy enough to go home soon after birth, or he may need to stay in the NICU for special care. Your baby can probably go home from the hospital when he:
- Weighs at least 4 pounds
- Can keep warm on his own, without the help of an incubator. An incubator is a clear plastic bed that helps keep your baby warm.
- Can breastfeed or bottle-feed
- Gains weight steadily
- Can breathe on his own
Your baby may need special medical equipment, medicine or other treatment after he leaves the hospital. Your baby’s provider and the staff at the hospital can help you with these things and teach you how to take care of your baby at home. They may recommend that you bring your baby to a neonatologist for checkups after your baby leaves the hospital. A neonatologist is a doctor who specializes in caring for premature babies and children. Talk to your baby’s provider if you have any questions about your baby’s health or long-term effects of premature birth. Hospital staff also can help you find parent support groups and other resources in your area that may be able to help you care for your baby.
What kinds of health problems can premature babies have?
Health problems that may affect premature babies include:
Anemia. This is when a baby doesn’t have enough healthy red blood cells to carry oxygen to the rest of the body. Anemia can cause low levels of oxygen and glucose (sugar) in a baby’s blood and make it hard for a baby’s organs to work properly. Premature babies in the NICU may have anemia because they get regular blood tests to check their health. They often can’t make new blood cells quickly enough to replace the blood cells they lose during blood tests. This can lead to anemia.
Breathing problems. These include:
- Apnea of prematurity (also called AOP). This is a pause in breathing for 15 to 20 seconds or more. It may happen together with a slow heart rate called bradycardia.
- Bronchopulmonary dysplasia (also called BPD). This is a lung disease that can develop in premature babies as well as babies who have treatment with a breathing machine. Babies with BPD have a higher risk of lung infections than other babies and BPD sometimes leads to lung damage.
- Respiratory distress syndrome (also called RDS). If a baby has RDS, her lungs can’t make enough of a substance called surfactant. Surfactant is a slippery substance that keeps small air sacs in a baby's lungs from collapsing.
Infections or neonatal sepsis. Premature babies can get infections more easily than other babies because their immune systems aren’t fully developed. The immune system protects your body from infection. Infection in premature babies can lead to sepsis, when the body has an extreme response to infection. Sepsis can be life-threatening.
Intraventricular hemorrhage (also called IVH). This is bleeding in the fluid-filled spaces (also called ventricles) in the brain. The more premature a baby is, the more likely he is to have IVH.
Newborn jaundice. This is when your baby’s skin and the white parts of his eye look yellow. It’s caused by the build-up of a substance called bilirubin in your baby’s blood. Jaundice happens when a baby’s liver isn't fully developed or isn't working well.
Necrotizing enterocolitis (also called NEC). This is a common, but very serious problem that can affect a newborn baby’s intestines. Intestines are long tubes that are part of your digestive system. Your baby’s digestive system helps his body break down food, take in nutrients and remove waste. NEC happens when the tissue of the intestine is injured (damaged) or begins to die.
Patent ductus arteriosus (also called PDA). This is a heart condition that happens when a blood vessel called the ductus arteriosus doesn’t close properly. The ductus arteriosus helps blood go around a baby’s lungs before birth. Once a baby’s born and her lungs fill with air, the ductus arteriosis isn’t needed anymore and usually closes on its own a few days after birth. If it doesn’t close properly, too much blood may flow into the lungs. This can cause heart and breathing problems.
Retinopathy of prematurity (also called ROP). This is an eye disease that happens when a baby’s retina’s don’t fully develop in the weeks after birth. The retina is the nerve tissue that lines the back of the eye. ROP usually affects both eyes. Most babies with ROP have a mild case and don’t need treatment. But babies with severe ROP can have vision problems or blindness.
Last reviewed: October, 2019