Parameters of linear mixed-effects models of agreement between CRL biometry and the Dubowitz method, the SFH formula, and HC or BPD biometry in estimating newborn gestational age.

Dubowitz and SFH models account for modification of agreement over birthweight-for-GA Z-score calculated using Dubowitz or SFH estimates of GA (mean-centred at 0) and estimated newborn GA (centred at 39 weeks). HC and BPD models account for modification of agreement over birthweight-for-GA Z-score calculated using HC/BPD estimates of GA (centred at 0), estimated newborn GA (centred at 39 weeks) and estimated gestation time of ultrasound measurement (centred at 25 weeks). Units are weeks for all values. [] – 95% limits of agreement. () – 95% confidence intervals. SD: standard deviation. These parameters can be used to calculate bias and limits of agreement in the absence of ultrasound CRL using the equations below: BiasDubowitz/SFH(95%LOA)=[β0+β1(Zscore)+β2(newbornGA−39)]±(2×SD)BiasHC/BPDbiometry(95%LOA)=[β0+β1(Zscore)+β2(newbornGA−39)+β3(GAatultrasound−25)]±(2×SD)Parameters of linear mixed-effects models of agreement between CRL biometry and the Dubowitz method, the SFH formula, and HC or BPD biometry in estimating newborn gestational age.