Estimating gestational age at birth: a population-based derivation-validation study

Introduction: Information on newborn gestational age (GA) is essential in research on perinatal and infant health, but it is not always available from administrative databases. We developed and validated a GA prediction model for singleton births for use in epidemiological studies. Methods: Derivation of estimated GA was calculated based on 130 328 newborn infants born in Ontario hospitals between 2007 and 2009, using linear regression analysis, with several infant and maternal characteristics as the predictor (independent) variables. The model was validated in a separate sample of 130 329 newborns. Results: The discriminative ability of the linear model based on infant birth weight and sex was reasonably approximate for infants born before the 37(th) week of gestation (r(2) = 0.67; 95% CI: 0.65-0.68), but not for term births (37-42 weeks; r(2) = 0.12; 95% CI: 0.12-0.13). Adding other infant and maternal characteristics did not improve the model discrimination. Conclusion: Newborn gestational age before 37 weeks can be reasonably approximated using locally available data on birth weight and sex.