Creating experiences from active treatment towards extremely preterm infants born at less than 25 weeks in Japan.

Treatment for extremely preterm infants born at less than 25 weeks of gestation in Japan was initiated mainly due to the amendment of the Maternal Health Act lowering the upper limit of abortion from 24 weeks to 22 weeks in 1990. Five years after the amendment, the Japanese national government started a nationwide project to improve the perinatal care system. Once selected perinatal centers reported improvements in survival rates, more centers have adopted aggressive treatments. They have accumulated their knowledge by experiencing the treatment of infants with a limit of viability. As a result, more than 50% of infants born even at 22 weeks of gestation can survive to discharge currently. This progress has resulted from the accumulation of experience at each perinatal center rather than the results from clinical trials. Furthermore, these experiences have been standardized to some extent through sharing information.