Final answer:
A hydatidiform mole on ultrasound appears as a cluster of grapelike structures without a fetal heartbeat or fetal parts. It may show a thickened placenta and may not show a gestational sac or a fetus.
Step-by-step explanation:
A hydatidiform mole, also known as a molar pregnancy, is not a normal pregnancy and occurs when there is an abnormal growth of cells in the uterus. On ultrasound, a hydatidiform mole presents as a mass that appears as a cluster of grapelike structures without a fetal heartbeat or fetal parts. The ultrasound image may show a thickened placenta and may not show a gestational sac or a fetus.