Individualized sex-specific birth weight percentiles for gestational age based on maternal height and weight.

OBJECTIVES: The maternal body size affects birth weight. The impact on birth weight percentiles is unknown. The objective of the study was to develop birth weight percentiles based on maternal height and weight. METHODS: This observational study analyzed 2.2 million singletons from the German Perinatal Survey. Data were stratified into 18 maternal height and weight groups. Sex-specific birth weight percentiles were calculated from 31 to 42 weeks and compared to percentiles from the complete dataset using the GAMLSS package for R statistics. RESULTS: Birth weight percentiles not considering maternal size showed 22% incidence of small for gestational age (SGA) and 2% incidence of large for gestational age (LGA) for the subgroup of newborns from petite mothers, compared to a 4% SGA and 26% LGA newborns from big mothers. The novel percentiles based on 18 groups stratified by maternal height and weight for both sexes showed significant differences between identical original percentiles. The differences were up to almost 800 g between identical percentiles for petite and big mothers. The 97th and 50th percentile from the group of petite mothers almost overlap with the 50th and 3rd percentile from the group of big mothers. CONCLUSIONS: There is a clinically significant difference in birth weight percentiles when stratified by maternal height and weight. It could be hypothesized that birth weight charts stratified by maternal anthropometry could provide higher specificity and more individual prediction of perinatal risks. The new percentiles may be used to evaluate estimated fetal as well as birth weight.

Individualized birth length and head circumference percentile charts based on maternal body weight and height.

Objectives Measurement of birth length and birth head circumference is part of the newborn assessment. Both measurements aid in distinguishing between proportionate and disproportionate small and large for gestational age newborns. It had been shown that birth weight is related to maternal height and weight. This study aims to analyze birth length and birth head circumference percentiles based on maternal stature. Methods This observational study analyzed birth length and birth head circumference percentiles of 2.3 million newborns stratified by maternal height and weight from the first obstetric assessment. Percentiles were calculated for sex and 22-43 gestational weeks for all infants. Eighteen subgroups based on six maternal height and three weight strata were defined and percentiles calculated from 32 to 42 gestational weeks using GAMLSS package for R. Results Newborns of mothers with height <158 cm and weight <53 kg (short stature) had a rate of preterm birth of 9%, compared to 5% in the tall stature group (height >177 cm, weight >79 kg). Small stature mothers were 1.7 years younger. Birth length differed by several centimeters for the same percentiles between groups of short and tall stature mothers, whereas birth head circumference differed up to 1.2 cm. The largest deviation of birth length was between the 97th percentiles. For male newborns born at term, birth length at the 97th percentile differed by 3.2 cm, at the 50th percentile by 2.7 cm and at the third percentile by 2.5 cm. Conclusions Birth length and birth head circumference are related to maternal height and weight. To more completely assess newborns, the maternal size should be considered.