Birthweight charts customised for maternal height optimises the classification of small and large-for-gestational age newborns

Abstract

Aim: To construct birthweight charts customised for maternal height and evaluate the effect of customization on SGA and LGA classification. Methods: Data were extracted (n = 21 350) from the MiCaS project in the Netherlands (2012–2020). We constructed the MiCaS-birthweight chart customised for maternal height using Hadlock's method. We defined seven 5-centimetre height categories from 153 to 157 cm until 183–187 cm and calculated SGA and LGA prevalences for each category, using MiCaS and current Dutch birthweight charts. Results: The MiCaS-chart showed substantially higher birthweight values between identical percentiles with increasing maternal height. In the Dutch birthweight chart, not customised for maternal height, the prevalence of SGA (<p10) decreased with increasing maternal height category, from 19.7% in the lowest height category to 3.4% in the highest category (range 16.3%). Conversely, the prevalence of LGA (>p90) increased with increasing height category, from 1.4% in the lowest height category to 21.8% in the highest category (range 20.4%). In the MiCaS-birthweight chart, SGA and LGA prevalences were more constant across maternal heights, similar to overall prevalences (SGA range 3.3% and LGA range 1.7%). Conclusion: Compared to the current Dutch birthweight chart, the MiCaS-birthweight chart customised for maternal height shows a more even distribution of SGA and LGA prevalences across maternal heights.