Clinical outcomes for babies born between 27 – 31 weeks of gestation: Should they be regarded as a single cohort?

Preterm babies born between 27 and 31 weeks of gestation are understudied and historically, have been grouped as a single cohort. Increased evidence relating to clinical outcomes is shaping models of care for babies born ≤26 weeks of gestation. Similar consideration of births between 27 and 31 weeks of gestation is now warranted. To address this, a clear understanding of the impact of progressive maturation in utero on the clinical care required, and on neonatal and infant outcomes of this group of preterm babies is helpful. In this review we highlight the spectrum of clinical presentations for babies born at 27–31 weeks of gestation. We discuss this with respect to key stages of organ/system development occurring in-utero during this five-week period and reveal a consistent trend of decreasing incidence of mortality and major morbidity with increasing gestational age at birth from 27 to 31 weeks. The clinical care required and the outcomes between babies born at either end of this gestational age range appear to be substantially different. This suggests it may be more appropriate to report outcomes by week of gestation rather than as a group in future research. Preterm health service delivery providers and decision makers need to consider this in planning services for the future, especially in environments where neonatal intensive care resources ought to be optimised for those at greatest need.