Perinatal & Pediatric
Association of maternal body mass index with longitudinal fetal growth assessed by three-dimensional ultrasonography Kathryn A. Wagner* Kathryn Wagner Jessica L. Gleason Zhen Chen Wesley Lee William A. Grobman Roger Newman Cuilin Zhang Stefanie Hinkle Luis Goncalves Seth Sherman Daniel W. Skupski Robert Gore-Langton Angela C. Ranzini Edward Chien Ronald Wapner Sabrina Craigo Jagteshwar Grewal Katherine L. Grantz
There is a current obesity epidemic in the US; from 2016-2019, there was an 11% increase in women entering pregnancy with obesity. Maternal obesity is associated with fetal overgrowth, as assessed by two-dimensional (2D) ultrasonography. However, 3D ultrasonography can characterize fetal lean and fat tissue and organ volumes, which may provide additional insight into fetal metabolic programming. Therefore, we evaluated fetal 3D measures across pregnancy by maternal pre-pregnancy BMI.
In the NICHD Fetal 3D Study (2015-2019), fetal body composition and organ volumes were measured at up to five ultrasound scans from 15-40 weeks by certified sonographers. BMI (kg/m2) was categorized as normal (18-<25; n=1567), overweight (25-<30; n=767), or obese (≥30; n=468), based on self-reported pre-pregnancy weight and height. Trajectories of fetal 3D measures were modeled using linear mixed effect models. Overall and weekly mean differences in fetal growth were tested across BMI category, adjusted for covariates.
Fetuses of women with overweight or obesity had significantly larger fractional arm and thigh volumes, from 25-26 weeks through 40 weeks, and larger abdominal area and maximum abdominal subcutaneous tissue thickness (SCTT) between 29-40 weeks, compared to women with normal BMI. Proportional to fractional limb volume, fetuses of women with obesity had significantly smaller lean but larger fat limb volumes from 15-34 weeks. Fetuses of women with overweight BMI had significantly larger lung volume from 22-31 weeks, while fetuses of those with obesity had significantly smaller lung volume from 17-20 weeks, compared to normal BMI. No overall differences were observed among limb SCTT or other organ volumes.
Fetuses of women with obesity had larger abdominal and limb measures, characterized by greater fat but less lean tissue accumulation, compared to normal BMI. Higher fat to lean tissue ratio may have implications for risk of cardiometabolic dysfunction across the life course.