Neonatal mortality risk of large-for-gestational-age and macrosomic live births in 15 countries, including 115.6 million nationwide linked records, 2000-2020

Objective: We aimed to compare the prevalence and neonatal mortality associated with large for gestational age (LGA) and macrosomia among 115.6 million live births in 15 countries, between 2000 and 2020.Design: Population-based, multi-country study.Setting: National healthcare systems.Population: Liveborn infants.Methods: We used individual-level data identified for the Vulnerable Newborn Measurement Collaboration. We calculated the prevalence and relative risk (RR) of neonatal mortality among live births born at term + LGA (>90th centile, and also >95th and >97th centiles when the data were available) versus term + appropriate for gestational age (AGA, 10th-90th centiles) and macrosomic (>= 4000, >= 4500 and >= 5000 g, regardless of gestational age) versus 2500-3999 g. INTERGROWTH 21st served as the reference population.Main outcome measures: Prevalence and neonatal mortality risks.Results:Large for gestational age was common (median prevalence 18.2%; interquartile range, IQR, 13.5%-22.0%), and overall was associated with a lower neonatal mortality risk compared with AGA (RR 0.83, 95% CI 0.77-0.89). Around one in ten babies were >= 4000 g (median prevalence 9.6% (IQR 6.4%-13.3%), with 1.2% (IQR 0.7%-2.0%) >= 4500 g and with 0.2% (IQR 0.1%-0.2%) >= 5000 g). Overall, macrosomia of >= 4000 g was not associated with increased neonatal mortality risk (RR 0.80, 95% CI 0.69-0.94); however, a higher risk was observed for birthweights of >= 4500 g (RR 1.52, 95% CI 1.10-2.11) and >= 5000 g (RR 4.54, 95% CI 2.58-7.99), compared with birthweights of 2500-3999 g, with the highest risk observed in the first 7 days of life.Conclusions: In this population, birthweight of >= 4500 g was the most useful marker for early mortality risk in big babies and could be used to guide clinical management decisions.