Dependence of neonatal small and large for gestational age rates on maternal height and weight--an analysis of the German Perinatal Survey.

Neonatal anthropometric data reflect intrauterine development and correlate with postnatal outcome. Therefore, classification of neonates by body dimensions, using gestational age-adjusted population percentiles, is clinically practiced. However, neonatal anthropometric variables are also influenced by maternal constitution and the extent of this influence is currently unknown. We analyzed small for gestational age (SGA) and large for gestational age (LGA) rates according to maternal height and weight. We used data of about 2.3 million singleton pregnancies from the German Perinatal Survey of 1995-2000. A close correlation between maternal and neonatal anthropometric data was found; SGA rates were inversely proportional and LGA rates were directly proportional to maternal height, weight, and body mass index. Neonates of small and light mothers (<155 cm, <50 kg) had, according to the presently used classification scheme, an SGA rate of 25.3% and an LGA rate of 1.7%, respectively. Newborns to tall and heavy women (>179 cm, >89 kg) had a much lower SGA rate (3.1%) and a much higher LGA rate (30.6%). Neonatal body length and head circumference depended on maternal stature in a similar way. Some neonates who are "appropriate" for their gestational age in that they achieve their genetically determined growth potential are therefore apparently misclassified as SGA or LGA.