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CME Credit Offered
CME Credit Offered
Abstract Award
Abstract Award
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Poster Session 3

(799) Association of maternal body mass index with longitudinal fetal growth assessed by three-dimensional ultrasonography

Friday, January 31, 2025
10:30 AM – 12:30 PM  
Objective: The current obesity epidemic is a major public health concern; 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 than 2D. Therefore, we evaluated fetal 3D measures across pregnancy by maternal pre-pregnancy BMI.

Study Design: 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), based on self-reported pre-pregnancy weight and height, were categorized as normal (18-< 25; n=1567), overweight (25-< 30; n=767), or obese (≥30; n=468). Trajectories of fetal 3D measurements were modeled using linear mixed effect models. Overall and weekly mean differences in fetal growth were tested by BMI group, adjusted for covariates.

Results: Fetuses of women with overweight or obesity, compared to women with normal BMI, had significantly larger fractional arm and thigh volumes, starting at 25-26 weeks and continuing through gestation. Proportional to fractional limb volume, fetuses of women with obesity had significantly smaller lean but larger fat limb volumes. Additionally, for overweight and obese groups, fetuses had significantly larger abdominal area and maximum abdominal subcutaneous tissue thickness (SCTT) from 29 weeks onward. Fetuses of women with overweight BMI had significantly larger lung volume from 22-31 weeks, while those with obesity had significantly smaller lung volume from 17-20 weeks, compared to those with normal BMI. No overall differences were observed among limb SCTT or other organs.

Conclusion: Fetuses of mothers with obesity had relatively smaller lean tissue but greater fat tissue accumulation throughout gestation, compared to normal BMI. Future research should examine whether fetal soft tissue differences may relate to metabolic dysfunction across the life course.