Relationship between gestational weight gain with fetal body composition and organ volumes in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Fetal Dimensional Study: a prospective pregnancy cohort.

BACKGROUND

Inadequate and excessive gestational weight gain (GWG) are associated with increased risk of newborn small- and large-for-gestational-age, respectively, and future offspring adiposity. However, the relationship between GWG and three-dimensional (3D) measures of fetal body composition and organ volumes, which may provide greater insight into fetal growth via measurement of soft tissue, remains unknown.

OBJECTIVES

The objective of this study was to examine the relationship between trimester-specific GWG and 3D fetal body composition and organ volume measurements.

METHODS

In a diverse, US prospective pregnancy cohort, trimester-specific GWG was calculated as difference between maternal weight at beginning and end of each trimester, and categorized as inadequate, adequate, or excessive, per 2009 Institute of Medicine (IOM) guidelines. Up to five 3D ultrasound scans were completed across gestation, from which fetal body composition and organ volume measurements were obtained (n = 2675 pregnancies). The associations between trimester-specific GWG categories and 3D fetal body composition and organ volumes were assessed at 15, 29, and 39 weeks.

RESULTS

Excessive compared with adequate GWG, in first and second trimesters was associated with larger abdominal circumference (n = 2430; 1st trimester: 1.29 cm, 95% CI: 0.74, 1.84; 2nd trimester: 2.98 cm, 95% CI: 1.62, 4.34) and abdominal area (n = 2401; 1st trimester: 22.04 mm, 95% CI: 0.48, 43.60; 2nd trimester: 162.34 mm, 95% CI: 76.25, 248.44), whereas excessive GWG in the first trimester was associated with larger arm subcutaneous tissue thickness (n = 1921; 0.01 cm, 95% CI: 0.00, 0.01). There was a trend toward increased fetal arm, thigh, kidney, and liver volumes and abdominal subcutaneous tissue, although differences did not reach the level of statistical significance for these structures.

CONCLUSIONS

Excessive GWG was associated with greater fetal size primarily manifested by a pattern of fat accumulation across the fetal arm and abdomen. Future studies should examine whether these fetal changes have functional implications for childhood adiposity and metabolic dysfunction. This trial was registered at https://clinicaltrials.gov as NCT00912132 and NCT03266198.