Bioelectrical Impedance Analysis

BIA is practical, non-invasive, portable and cost-effective for community studies, and AWGS supports its use when DXA is not feasible. DXA is the reference standard for body composition, and BIA can systematically overestimate or underestimate muscle mass depending on device, population and prediction equation. The sarcopenia assessment methods were selected for being simple, non-invasive, and not time-consuming, with the intent that they could translate to routine clinical practice. BIA has already been used in multiple pregnancy studies, supporting its applicability in this population. BIA estimates not only skeletal muscle mass but also lean mass, fat mass, intracellular and extracellular water, and dry lean mass. Skeletal Muscle Index is calculated as appendicular skeletal muscle mass divided by height squared in kg/m². Muscle mass in the SiGnal-D study is assessed using bioelectrical impedance analysis with a body composition analyser specifically indicated for use during pregnancy.