Association of maternal pregravid body mass index with growth of fetal fractional limb volume

Maternal obesity influences birthweight and newborn adiposity. Fetal fractional limb volume has been introduced as a useful parameter for the proxy of fetal adiposity. However, he association between maternal adiposity and the growth of fetal fractional limb volume has not been examined. This study aimed to define the effect of maternal adiposity on the growth of fractional limb volume. Women with singleton pregnancies were enrolled between July 2017 and June 2020. Fetal fractional limb volume was assessed between 20 and 40 weeks of gestation. Fractional limb volume was measured as cylindrical limb volume based on 50% of the total diaphysis length. The measured fractional limb volume at each gestational week were converted to z-scores based on a previous report. Multiple linear regression was used to quantify the association between pre-pregnancy BMI and fractional arm volume and thigh volume, with adjustment for potential confounding variables including maternal age, parity, gestational weight gain and infant sex. Ultrasound scans of 466 fractional arm volume and thigh volume were obtained. Maternal pre-pregnancy BMI was significantly correlated with z-scores of fractional arm volume and thigh volume across gestation. The posthoc analysis showed the correlation was significant between 28 and 40 weeks for fractional arm volume, and between 20 and 27 weeks for fractional thigh volume. Maternal obesity influences the growth pattern of fetal fractional limb volume. Fractional arm volume is associated with maternal adiposity in the third trimester of gestation. Fractional arm volume may potentially provide a useful surrogate marker of fetal nutritional status in late gestation.