Split-week gestational age model provides valuable information on outcomes in extremely preterm infants.

AIM: To compare composite outcomes of neonatal mortality or morbidity using a split-week gestational age (GA) model to completed weeks GA maturity at 23-26 weeks gestation. METHODS: This was a retrospective cohort study of infants born at 23 to 26 weeks GA. Outcomes using a split-week GA model defined as early (X, 0-3) and late (X, 4-6) with X being 23-26 weeks GA were compared to outcomes using completed weeks GA, with a similar comparison between the late split of the preceding week (X, 4-6) and early split of the subsequent week (X+1, 0-3). RESULTS: 1345 infants were included in the study. Statistically significant differences were noted in outcomes between the early and late split of the gestational week at 24 (early vs. late, 85.6 % vs. 73.0 %), 25 (69.6 % vs. 56.6 %) and 26 weeks (55.9 % vs. 37.4 %), but not at 23 weeks GA (95.2 % vs. 94.5). No statistically significant differences were noted between the late versus early part of the subsequent week (23, 4-6) versus (24, 0-3), and (24, 4-6) versus (25, 0-3) GA. CONCLUSION: Neonatal outcome estimates using a split week model differs from that based on the use of completed weeks of gestational maturity.