Objective: To derive models and equations for estimating fetal lean mass and fat mass in women with gestational diabetes mellitus (GDM), using sonographic techniques and neonatal total body electrical conductivity.
Methods: Twenty women with GDM at term underwent sonographic evaluation within 72 hours before delivery. Sonographic studies included measurements of the fetal biparietal diameter, head circumference, abdominal circumference, anterior and lateral abdominal-wall subcutaneous fat thicknesses, femur length, mid-thigh circumference, and anterior and lateral thigh subcutaneous fat thicknesses. Within 24 hours of birth, the infants were weighed and their body composition estimated with total body electrical conductivity measurements. Volume-based models and regression equations for estimating lean and fat mass were derived. The equations were validated prospectively in the next 16 women with GDM.
Results: There were no significant differences in maternal or neonatal demographic or anthropometric data between the derivative and validation groups. The equation for estimating fetal lean mass is: lean mass = 0.169(volume of head) + 0.262(volume of lean trunk) - 308.59 (r = 0.86, P < .01). The equation for estimating fetal fat mass is: fat mass = 0.241(volume of fat sheath of trunk) - 213.13 (r = 0.73, P < .01). In the validation group, the sonographic estimates of fetal lean and fat mass were not significantly different than those estimated by total body electrical conductivity (P = .18 and P = .77, respectively).
Conclusion: Fetal body composition can be estimated by obtaining several additional measurements during routine fetal sonography.