Preterm birth, which occurs anytime up to 37 weeks, is the biggest cause of newborn deaths and the leading cause of death in children under five. Globally more than 15 million babies are born prematurely every year, which is more than 1 in 10 babies and this number is rising. Around 1 million of preterm babies die each year from related complications.
However even the survivors are at risk – they are more likely to have cerebral palsy, delays in development, respiratory conditions and visual and hearing problems. Survival rates vary enormously: for babies born before 23 weeks it is less than 1%, it increases at 23 weeks to 15%. But after this every extra day in the womb increases the chance of survival: at 24 weeks it is 55% while at 25 weeks it is about 80%.
The causes of preterm birth vary. Most preterm births occur spontaneously. In 20% of cases the mother’s waters break early leading to birth. An emergency event such as infection, the placenta detaching from the uterus, eclampsia or the umbilical cord leaving the mother’s body before the baby accounts for another 25%. Not all birth prematurity is unplanned, in a quarter of cases either the mother or the baby or both are experiencing life-threatening complications such as pre-eclampsia, kidney disease or growth restriction. However in 40% of cases the cause is a mystery.
Risk factors include the mother having diabetes, high blood pressure, being pregnant with multiple babies, either being obese or underweight, having a vaginal infection, smoking and stress. However, genetics are also implicated and there is increasing evidence that the mother’s genetic make-up can result in prematurity but surprisingly genetic mutations in the baby itself can lead to preterm birth.
Survival rates of preterm babies are very dependent on where the babies are born. In low-income countries, 90% babies born before 28 weeks will die within a few days of life compared with only 10% dying in high-income countries. This is mainly due to a lack of cost-effective care such as warmth through skin-to-skin contact, ‘frequent breastfeeding’ support and basic care for newborn infections and breathing difficulties. Help can be provided before birth by giving pregnant women at risk of preterm labour steroid injections which help strengthen the babies’ lungs.
Preterm birth remains a major public health issue because doctors and researchers do not fully understand its many causes, and unlike most medical challenges the problem is getting worse.
Liu et al. Global, regional and national causes of child mortality in 2000-13, with projections to inform post-2015 priorities: an updated systematic analysis. Lancet 2015 385, 430-440.
Tommy’s. Premature birth statistics. 2016. Available at: https://www.tommys.org/our-organisation/why-we-exist/premature-birth-statistics (accessed 30 May 2016).
World Health Organisation. Preterm Birth. 2015. Available at: http://www.who.int/mediacentre/factsheets/fs363/en/ (accessed 30 May 2016).