According to World Health Organization (WHO) estimates, prematurity is the leading underlying cause of death in children under five years, with over one million babies dying each year worldwide due to complications of preterm birth. For those who survive, the consequences of being born too soon can continue throughout the life course, impacting individuals, families and communities.
Preterm birth, which is distinct from small-for-gestational age, is defined as live birth before 37 weeks of pregnancy are completed, and is classified by the following gestational ages:
- Extremely preterm (<28 weeks)
- Very preterm (28 to <32 weeks)
- Moderate to late preterm (32 to <37 weeks)
The rates of prematurity are rising around the world. Of the 15 million babies born preterm every year, 60% occur in Africa and South Asia. A baby’s risk of death due to prematurity depends largely on where he or she is born: In high-income countries, 50% of babies born at less than 28 weeks survive, while half of babies born at 32 weeks die in low-income countries. Moderate or late preterm babies can often be cared for effectively with simple, low-cost, evidence-based methods requiring limited technology, such as kangaroo mother care and feeding support.
Although the causes of preterm birth are complex, risk factors include maternal smoking and substance abuse, adolescent pregnancy, infections like syphilis, Group B streptococcus and malaria, pre-eclampsia, bleeding in pregnancy and premature rupture of membranes. High quality preconception and prenatal care are key factors in preventing preterm delivery. Furthermore, social determinants can greatly influence the likelihood that a woman will delivery prematurely. Disparities in preterm birth by factors such as socioeconomic status and race persist. For example, in the United States, the risk of premature delivery is three times greater among black women compared to white women.
There are a number of challenges related to the management, prevention and treatment of preterm births, particularly with pregnancy dating. Last menstrual period is often unknown or unreliable, and until recently, there were no international standards for relating ultrasound measurement of fetal crown-rump length to gestational age. Even with these new standards in place, access to ultrasound and trained sonographers in low-resource settings can be highly variable. Preventative strategies and early treatment can help mitigate the effects of preterm birth, but these practices require continued research. For example, while administering antenatal corticosteroids has been promoted as an effective way to prepare preterm babies’ immature lungs for life outside the womb in case of imminent preterm birth, the treatment is debated for its implementation challenges, including insufficient support for managing side effects. Additionally, early neurological development care for preterm newborns is an emerging field, but further evidence is needed to evaluate the efficacy of those interventions.
At the policy level, the global issue of preterm birth has gained momentum in recent years, especially through the Every Newborn Action Plan. New estimations suggest that scaling up evidence-based, low-cost interventions to prevent and manage prematurity could avert 70% of preterm deaths in low- and middle-income countries. However, scaling interventions for the mother-baby dyad in a way that provides equity in access and quality of care remains a crucial challenge.