Long-term health of babies born close to term

Preterm birth is defined as birth before 37 weeks of gestation and until recently, ‘full term’ has been used to refer to birth at or beyond 37 weeks of gestation. However, it has become clear in recent years that these definitions may require further thought and so preterm birth has been subject to reclassification and term birth to redefinition. So how and why has this challenge to established thinking come about?