A customized standard to assess fetal growth in a US population

OBJECTIVE: The objective of the study was to assess the factors that affect fetal growth and birthweight, and to derive coefficients for a customized growth chart applicable in an American population. STUDY DESIGN: This was a prospective cohort study of 35,235 pregnancies. Coefficients for physiological and pathological variables were derived by backward multiple regression. RESULTS: The expected birthweight at 40.0 weeks for a standard-size primiparous mother of European origin in an uncomplicated pregnancy was 3453.4 g, very similar to the standardized birthweight observed in other populations. Physiological coefficients were derived for maternal height, weight, parity, ethnic origin, and sex of the baby. Smoking, history of preterm delivery, and hypertensive diseases in the current pregnancy all had negative effects on birthweight, whereas babies of diabetic mothers weighed more. Low as well as high body mass index was associated with birthweight deficit at term. CONCLUSION: Coefficients that allow determination of the customized growth potential, individually adjusted and excluding known pathological factors, have been derived. Babies of obese mothers have an increased risk of not reaching their fetal growth potential.