Preterm birth is the most common cause of death among infants worldwide. About 15 million babies are preterm each year which represents 5 to 18% of all deliveries. Approximately 0.5% of births are extremely early periviable births, and these account for most of the deaths. In many countries, rates of preterm births have increased between the 1990s and 2010s. Complications from preterm births resulted in 0.81 million deaths in 2015 down from 1.57 million in 1990. The approximated chance of survival at 22 weeks is 6%, at 23 weeks it is 26%, at 24 weeks 55% and at 25 weeks 72%. The chances of survival without any long-term difficulties are however lower.