Background The risk of poor outcomes in preterm infants is primarily determined by birthweight (BW) and gestational age (GA). It is not known whether BW is a better outcome predictor than GA.
Objective To test whether BW is better than GA (measured in days, rather than completed weeks) for prediction of neurodevelopmental impairment (NDI) and death.
Design/methods Extremely preterm infants born at the National Institute of Child Health and Human Development (NICHD) Neonatal Research Network centres between 1998 and 2009 were studied. For the unadjusted analysis, the associations of GA (in days based on best obstetrical estimate) and BW (in grams) with NDI or death were compared using area under the curve (AUC). Adjusted analyses were performed using birth year, sex, race, antenatal steroids, singleton birth, pre-eclampsia, Apgar score at 5 min and small for GA as covariates.
Results 10 652 preterm infants (89%) had outcome data at 18–22 months’ corrected age. The mean BW was 678 g (SD: 155) and the mean GA was 173 days (SD: 10) or 245/7 weeks (SD: 13/7). The AUC for NDI or death was 80% with BW and 79% with GA (p=0.82). Unadjusted and adjusted analyses did not differ. NDI or death rates decreased with increasing GA through 26 weeks (estimated risk reduction with each additional day of gestation: 2.2%).
Conclusion Both BW in grams and GA in days are good predictors of NDI and death in a preterm population selected on the basis of reliable GA.
Trial registration number NCT00009633.
- outcome prediction
- risk stratification
- extremely-low-birth-weight infants
- extremely-low-gestational-age newborns
- premature infants
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Contributors AAS and WAC: conceptualised and designed the study, oversaw data analyses, drafted and revised the manuscript and approved the final manuscript as submitted. NA, BJS and RDH: assisted in study design, reviewed and revised the manuscript and approved the final manuscript as submitted. TLN and AD: assisted in study design, performed the statistical analyses, reviewed and revised the manuscript and approved the final manuscript as submitted.
Funding The NIH and the Eunice Kennedy Shriver National Institute of Child Health and Human Development provided grant support for the Neonatal Research Network's Generic Database Study and Follow-up Study. The authors were supported by grants from the National Institute of Child Health and Human Development and the Department of Health and Human Services (U10 HD21364, U10 HD21373, U10 HD21385, U10 HD21397, U10 HD21415, U10 HD27851, U10 HD27853, U10 HD27856, U10 HD27871, U10 HD27880, U10 HD27881, U10 HD27904, U10 HD34216, U10 HD36790, U10 HD40461, U10 HD40492, U10 HD40498, U10 HD40521 and U10 HD40689) and from the National Institutes of Health (UL1 RR24139, UL1 RR24160, UL1 RR25008, M01 RR30, M01 RR32, M01 RR39, M01 RR44, M01 RR70, M01 RR80, M01 RR125, M01 RR633, M01 RR750, M01 RR997, M01 RR6022, M01 RR7122, M01 RR8084 and M01 RR16587).
Competing interests None declared.
Ethics approval Institutional Review Board.
Provenance and peer review Not commissioned; externally peer reviewed.