[1] During a molar pregnancy, the uterus contains a growing mass characterized by swollen chorionic villi, resembling clusters of grapes.

[2] The occurrence of a molar pregnancy can be attributed to the fertilized egg lacking an original maternal nucleus.

On the other hand, a partial mole occurs when a normal egg is fertilized by one or two sperm, which then reduplicates itself, resulting in genotypes of 69,XXY (triploid) or 92,XXXY (tetraploid).

Potential risk factors may include defects in the egg, abnormalities within the uterus, or nutritional deficiencies.

Other risk factors include diets low in protein, folic acid, and carotene.

[7] The diploid set of sperm-only DNA means that all chromosomes have sperm-patterned methylation suppression of genes.

[8] A hydatidiform mole is a pregnancy/conceptus in which the placenta contains grapelike vesicles (small sacs) that are usually visible to the naked eye.

Under careful surveillance, it is often possible for the woman to give birth to the normal child and to be cured of the mole.

In approximately 20% of complete moles, the most probable mechanism is that an empty egg is fertilized by two sperm.

A small percentage of hydatidiform moles have biparental diploid genomes, as in normal living persons; they have two sets of chromosomes, one inherited from each biological parent.

Some of these moles occur in women who carry mutations in the gene NLRP7, predisposing them towards molar pregnancy.

[15] Sometimes symptoms of hyperthyroidism are seen, due to the extremely high levels of hCG, which can mimic the effects of thyroid-stimulating hormone.

In 2 to 3% of cases, hydatidiform moles may develop into choriocarcinoma, which is a malignant, rapidly growing, and metastatic (spreading) form of cancer.

Over 90% of women with malignant, non-spreading cancer are able to survive and retain their ability to conceive and bear children.

In those with metastatic (spreading) cancer, remission remains at 75 to 85%, although their childbearing ability is usually lost.

The etymology is derived from hydatisia (Greek "a drop of water"), referring to the watery contents of the cysts, and mole (from Latin mola = millstone/false conception).