Objective: This study aimed to verify whether Hadlock's reference values for fetal weight identify fetuses below the 10th percentile in our population correctly.
Methods: The fitness of the Hadlock reference range to our study population was tested by assessment of Z scores. We evaluated differences between the reference weight ranges proposed in our study and those recommended by Hadlock.
Results: Z scores for Hadlock reference values were non-normally distributed. The difference between the 50th percentile fetal weight proposed by our study model and that proposed by Hadlock was ≤1% at GAs ≥22 weeks and 2-3% at 19-21 weeks. For the 90th percentile level, the maximum difference at GAs ≥17 weeks was 1.5%. For the 10th percentile level, the differences were 2-4% in the third trimester, reaching 8% in week 20 and 13% at a GA of 14 weeks.
Conclusions: The weight reference ranges of this study virtually overlap with the Hadlock ranges. We believe that only at lower gestational ages in the second trimester might some FGR diagnoses be missed in the population study with Hadlock's reference.
Keywords: FGR; Fetal weight; growth restriction; reference values; ultrasonography.