The numerical pregnant body models (A,B) and the numerical model of the two-channel, 32-rung high pass birdcage coil (C) used in this study. BCH2 has twin pregnancy. BCH4 and BCH5 are generated from the same pregnant woman scanned in supine and left lateral postures, respectively. BCH4-2-1, BCH4-2-2, BCH4-2-3, and BCH4-2-4 are manually generated from BCH4-1-1 by removing the arms and by removing the arms and rotating the fetus by 20°, 160°, and 180°, respectively. BMI, body mass index; GA, gestational age; w, weeks