Changes in abdominal adipose tissues and ectopic fat depots during pregnancy are dissociated from gestational weight gain.

Objective: The study objective was to evaluate changes in abdominal adipose tissue and ectopic fat during pregnancy and their associations with gestational weight gain (GWG) in women with overweight/obesity.

Methods: This study was a secondary analysis of a randomized controlled trial. Magnetic resonance scans were performed during gestational week (GW) 15, GW 32, and around birth to measure abdominal subcutaneous (SAT) and visceral (VAT) adipose tissues, liver fat, and muscle fat. Linear mixed models and multivariable linear regression analyses were utilized, adjusting for prepregnancy BMI, parity, and randomization.

Results: Among 119 women, VAT and SAT decreased from GW 15 to GW 32 but rebounded at birth; final levels were lower than at GW 15. Liver fat and muscle fat did not change significantly. GWG was positively associated with changes in SAT but not with those in VAT, liver fat, or muscle fat.

Conclusions: This study demonstrates dynamic changes in abdominal fat depots during pregnancy in women with overweight/obesity. The observed reduction in VAT and SAT during pregnancy and the association of GWG with SAT suggest that weight gain during pregnancy may be less metabolically harmful than outside pregnancy. Future research should investigate the mechanisms and long-term effects on maternal and child health.