Fetal 3D Study

Eunice Kennedy Shriver National Institute Of Child Health & Human Development

Investigators

Linked publications & trials

Abstract

The Fetal 3D Study team published a study design paper that describes the study design, methods and details about reviewer training and fetal biometric measurement. Basic characteristics of this cohort, with their corresponding distributions of fetal 3D measurements by anatomic structure, are summarized. (Grantz et al. American Journal of Epidemiology, 2024) Notably there was generally good agreement between the two reviews for the fetal limb structures, although were slightly higher for the fractional lean limb volumes and high for the subcutaneous tissue thickness measures. Our findings are consistent with prior work that indicates fractional arm volume (AVol) and fractional thigh volume (TVol) measurements are reproducible during the second and third trimesters of pregnancy. We also established standards for fetal soft tissue and organ volume measurements by three-dimensional ultrasonography and compared growth trajectories with conventional two-dimensional measures where applicable. (Grantz et al. American Journal of Obstetrics & Gynecology, 2025) Notably, growth patterns and timing of maximal growth for three-dimensional lean and fat measures, limb and organ volumes differed from patterns revealed by traditional two-dimensional growth measures, suggesting these parameters reflect unique facets of fetal growth. Growth in these three-dimensional measures may be altered by genetic, nutritional, metabolic or environmental influences and pregnancy complications, in ways that are not identifiable using corresponding two-dimensional measures. Our team followed up this work to investigate serial changes in fetal subcutaneous fat, lean body mass and organ volume in association with pregnancy complications. Previously we found that in pregnancies with gestational diabetes mellitus (GDM) compared with no GDM, fetuses had larger fractional arm volume and abdominal measures, manifested by increases in fat tissue, from the second trimester through gestation, independent of pre-pregnancy BMI. (Wagner et al. Diabetes Care 2024) Patterns were similar among fetuses of women with impaired glucose tolerance but with a larger magnitude. These findings suggest that hyperglycemia during pregnancy, even hyperglycemia not reaching GDM diagnostic thresholds, may affect the distribution of fetal fat accumulation, often occurring prior to clinical GDM diagnosis at 24-28 weeks gestation. In a recent study, excessive gestational weight gain was associated with greater fetal size primarily manifested by a pattern of fat accumulation across the fetal arm and abdomen. (Wagner et al. Am J Clin Nutr. 2025) Future studies are needed to examine whether these fetal changes have functional implications for childhood adiposity and metabolic dysfunction. Real time identification of accelerated fat deposition in the fetus may be a signal to initiate or adjust medical management, diet and physical activity to improve outcomes.