Measurement of the fetal cardiac GSI of gestational diabetes mothers at 32 gestational weeks. A longitudinal line is drawn from the apex to the base of the cardiac outer edge and a transverse line is drawn from the sidewall of the LV to the sidewall of the RV at the end of diastole. The GSI can be obtained by dividing the end-diastolic basal–apical length by the end-diastolic transverse width. GSI: global sphericity index; LV: left ventricle; RV: right ventricle