Maternal waist-to-hip ratio as a predictor of newborn size: Results of the Diana Project.

Location of body fat stores, as indicated by waist-to-hip circumference ratio (WHR), affects a variety of metabolic processes in women, and some of these changes could affect fetal growth during pregnancy. We tested the hypothesis that WHR affects fetal growth among 702 participants of the Diana Project, a prospective study designed to identify preconceptual exposures related to reproductive outcomes. We tested the effect of maternal WHR on the outcomes of infant birthweight, length, and head circumference in regressional models that included 16 variables such as maternal body mass index, duration of gestation, and pregnancy weight gain previously related to birthweight. Maternal WHR was related to each measure of newborn size. A 0.1-unit increase in WHR predicts a 120-gm greater birthweight, a 0.2-inch greater length, and a 0.3-cm greater head circumference. We conclude that WHR is related to fetal growth and that the effect of WHR on fetal growth may be mediated by metabolic alterations associated with a preponderance of central body fat stores or to other factors closely aligned with WHR. The common finding of an independent effect of pregnancy BMI on birthweight may be largely attributable to maternal WHR.