图示：葡萄胎。不常见的，受精时母性染色体丢失，核型为46XX， 仅由父性染色体构成，虽然能够形成胎盘，但不能形成胎儿，因此形成葡萄状肿胀的绒毛组织。
This is a hydatidiform mole. Molar pregnancies are uncommon and occur when there is fertilization of an ovum by a sperm but loss of maternal chromosomes, leaving a 46XX karyotype composed only of paternal chromosomes, enough to form a placenta, but not a fetus. The result is a mass of tissue with grape-like swollen villi.