Final answer:
A sonographic snowstorm pattern resembling clusters of grapes is indicative of a molar pregnancy, which involves abnormal trophoblast growth that can be either a complete or partial molar pregnancy.
Step-by-step explanation:
The term associated with a sonographic appearance resembling a snowstorm pattern, often seen in clusters resembling grapes, is C. Molar pregnancy. A molar pregnancy occurs when there is an abnormal growth of trophoblasts, the cells that normally develop into the placenta. There are two types of molar pregnancies: complete and partial. In a complete molar pregnancy, there is no formation of normal placental tissue or fetus, and the uterus is filled with a mass of cysts. In a partial molar pregnancy, there may be abnormal placental tissue along with an abnormal fetus.
In the context of ectopic pregnancies, the embryo does not reach the uterus but instead, implants in the uterine tube, with tubal pregnancy being the most common form. However, an ectopic pregnancy does not present a snowstorm pattern on ultrasound, which is characteristic of a molar pregnancy.