Trends in sex differences in neurodevelopmental outcomes among extremely preterm infants

Objective To examine whether changes in survival without moderate or severe neurodevelopmental impairment (NDI) at 18-26 months' corrected age from 1999 to 2018 differed between male and female infants.Design This retrospective cohort study used data from the NICHD Neonatal Research Network hospitals. Robust Poisson regression models were used to estimate adjusted relative risks (aRRs) and 95% CIs for survival without moderate or severe NDI between males and females. Interactions between sex and time were assessed to evaluate temporal differences in the outcome by sex. Variables adjusted for included centre, maternal age, ethnicity/race, gestational age and small for gestational age.Patients Inborn infants with gestational age of 22-26 weeks at NICHD Neonatal Research Network hospitals from 1999 to 2018.Main outcome measure Change over time in survival without moderate or severe NDI at 18-26 months' corrected age between male and female infants.Results Of 26 307 infants, 13 045 (49.6%) were male. Survival without moderate or severe NDI declined for both sexes over time, from 32.9% to 30.6% for males and from 47.4% to 40.0% for females, between 1999-2003 and 2014-2018. Males were less likely than females to survive without moderate or severe NDI (aRR=0.80; 95% CI 0.78 to 0.83). Changes in survival without moderate or severe NDI did not differ between males and females.Conclusion There were no differential changes in survival without moderate or severe NDI between male and female infants.