Impact of maternal height on birthweight classification in singleton births at term: a cohort study in The Netherlands

Objective: To assess the association between maternal height and birthweight in a healthy population and to study the effect of maternal height on the classification of birthweight as small for gestational age (SGA) and large for gestational age (LGA). Methods: A descriptive, observational retrospective study was conducted in a low risk population in the Netherlands. The study included term singleton healthy nonsmoking pregnant women with normal body mass index (n = 9291). We calculated the impact of maternal height on birthweight using multiple linear regression analyses with adjustment for gestational age, gender, and parity. We calculated the number of newborns classified as SGA and LGA using the cutoff point of the Dutch Birthweight chart, which does not customize for maternal height. Subsequently, we calculated the changes in classification from SGA and LGA to appropriate for gestational age (AGA) in case of customization for maternal height. Results: A significant association was found between maternal height and birthweight; 15.0 g higher birthweight per extra cm maternal height (95% confidence interval 13.8–16.1; p<.001; R ² model = 0.28). The incidence of SGA was 7.1% (range 17.4–2.0% form shortest to tallest maternal height category) and of LGA 8.4% (range 1.9–21.5% from shortest to tallest maternal height category). We calculated a shift in classification: 114 newborns (17.3%) in shorter (<167 cm) women previously SGA and 165 newborns (21.1%) in taller (>173 cm) women previously LGA were classified as AGA when controlling for maternal height. Conclusions: Maternal height is significantly associated with birthweight. Birthweight charts customized for maternal height change classification in one out of six SGA or LGA newborns at term.