Survival prediction modelling in extreme prematurity: are days important?

J Perinatol. 2022 Feb;42(2):177-180. doi: 10.1038/s41372-021-01208-1. Epub 2021 Sep 17.


Objective: To demonstrate that days are important in extreme prematurity when creating survival prediction models based on gestation.

Study design: Prospectively collected data were analysed for all admitted infants born 23 + 0 to 27 + 6 weeks gestation in the Australian and New Zealand Neonatal Network from 2009 to 2016. The effect of days on observed survival rates was assessed using a non-parametric test for trend. Prediction models created based on gestational age in completed weeks only or weeks plus days were compared.

Result: Seven thousand eight hundred and thirty-six extreme preterm infants were studied. Observed survival increased with days for 23, 24, 25, and 27 weeks gestational age (P = 0.01; P < 0.001; P = 0.003; P = 0.003) but not for 26 weeks (P = 0.19). A survival prediction model based on weeks and days performed better than completed weeks only (AUC 0.722 vs 0.712; P < 0.001).

Conclusion: In extreme prematurity, survival estimate accuracy improves when survival prediction models include days in addition to weeks.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Australia / epidemiology
  • Gestational Age
  • Humans
  • Infant
  • Infant, Low Birth Weight
  • Infant, Newborn
  • Infant, Premature*
  • Infant, Premature, Diseases*