Objective: To estimate observed compared with predicted survival rates of extremely premature infants born during 2000-2009, to identify contemporary predictors of survival, and to determine if improved survival rates occurred during the decade.
Methods: We conducted a retrospective cohort analysis of 237 inborn neonates without major congenital anomalies born from 2000 to 2009 after 22 to 25 completed weeks of gestation. Observed survival rates at each gestational age were compared with predicted survival rates based on gestational age, birth weight, sex, singleton or multiple gestation, and antenatal corticosteroid administration estimated by a Web-based calculator that was derived from 1998 to 2003 outcomes of a large national cohort. Multivariable logistic regression analysis was used to identify significant predictors of survival of the study cohort, including year of birth.
Results: Survival rates for the decade by gestational age (compared with predicted rates) were: 22 weeks, 33% (compared with 19%); 23 weeks, 58% (compared with 38%); 24 weeks, 87% (compared with 58%); and 25 weeks, 85% (compared with 70%). Antenatal corticosteroids were administered in 96% of pregnancies. Variables that significantly predicted survival and their odds ratios (OR) with 95% confidence intervals (CI) are: antenatal corticosteroid administration (OR 5.27, CI 1.26-22.08); female sex (OR 3.21, CI 1.42-7.26); gestational age (OR 1.89, CI 1.27-2.81); 1-minute Apgar score (OR 1.39, CI 1.15-1.69); and birth year (OR 1.17, CI 1.02-1.34). The number needed to treat with any antenatal corticosteroid therapy to prevent one death was 2.4.
Conclusion: In this single-institution cohort treated aggressively (antenatal corticosteroid administration [even if less than 24 weeks], tocolysis until steroid course complete, cesarean for fetal distress) by perinatologists and neonatologists, survival rates at 22-25 weeks of gestation age for inborn infants during the 2000s exceeded predicted rates, with increasing odds of survival during the decade. Antenatal corticosteroid administration had a significant effect on survival.
Level of evidence: II.