We present a case of uterine synechia diagnosed by conventional 2-D color Doppler, 3-D sonography, and magnetic resonance imaging at 26 weeks' gestation. 3-D sonography clearly revealed umbilical cord prolapse through an oblique transverse uterine synechia. Loops of the umbilical cord were below and the fetus was superior to the uterine synechia. The edge of the umbilical cord loops was attached to the amniotic membrane, and a small echo-free space was noted beneath the attachment. 2-D color Doppler showed arterial blood flow consistent with the maternal heart rate. Magnetic resonance imaging confirmed the oblique horizontal membrane dividing the uterus with umbilical cord prolapse, its attachment to the amniotic membrane, and a small echo-free space in the low, liquor-filled amniotic cavity. We demonstrate how 3-D sonography provided a novel visual depiction of uterine synechia, which greatly helped in prenatal diagnosis and counseling.