Grape-like vesicles

Sometimes, the father contributes excessive genetic material to the conceptus (the product of union of the egg and sperm). This occurs for example, when an ‘empty’ ovum (lacking the mother’s genetic material apart from mitochondrial genes) is fertilized by a single sperm which then duplicates its genetic material, or when two sperms fertilize an ‘empty’ ovum or further still when two sperms fertilize an apparently normal ovum. These situations in which there is surplus paternal genetic material may result in molar pregnancy (hydatidiform mole) characterized by a placenta with vesicles that resemble clusters of grapes – grape-like vesicles.
Placental mesenchymal dysplasia is another condition that can give grape-like vesicles

Reference:

Berkowitz RS, Goldstein DP: Clinical practice. Molar pregnancy. N Engl J Med, 2009 360(16):1639-45. Go to reference