Preterm birth is defined by the WHO as birth before 37 completed weeks of gestation. The incidence varies across countries but is currently approximately 8% of all births in the United Kingdom and 11% worldwide. Being born too soon can confer significant clinical deficits throughout life, leading to neuro-developmental disorders such as cerebral palsy, learning impairment and visual disorders; problems which are more likely to occur with greater severity at earlier gestations of birth [1]. Preterm birth may also affect long-term physical health, with a higher risk of cardiovascular disease, and lays a huge emotional and economic burden on affected families [2]. Figure 39.1 is adapted from the EPICURE longitudinal study of morbidity and mortality of preterm infants and demonstrates that with each week of increasing gestation, rates of disability and death decrease substantially. This underlines the importance of timely treatment aimed at preventing and ameliorating the effects of preterm birth.