Hydatidiform Mole

I. Definition A molar pregnancy is an abnormal form of pregnancy in which a non-viable fertilized egg implants in the uterus, converting the normal pregnancy progress into a pathological one. It is characterized by the presence of a hydatidiform mole, which the chorionic villi around the fetus degenerate and form clusters of fluid-filled sacs, resulting in tumor growth that forms in the uterus as a bunch of cysts resembling grape-like vesicles that are visible to the naked eye. Hydatidiform mole (also known as hydatid mole or mola hydatidosa) is type a gestational trophoblastic disease that results from over-production of the tissue that is supposed to develop into the placenta. It is derived from the Greek word hydatisia which means “a drop of water”, referring to the watery contents of the cysts, and the Latin word mola which means “false conception”. The conception of a hydatidiform mole may be categorized as one type of non-induced/natural missed abortion or a missed miscarriage, because the pregnancy has become non-viable (miscarried) but was not immediately expelled (missed). There are two types of hydatidiform mole: partial and complete. In a normal pregnancy, the egg receives one set of 23 chromosomes from the father and one set of 23 chromosomes from the mother, for a total of 46 chromosomes. A partial mole occurs when an egg is fertilized by two sperm or by one sperm which reduplicates itself, yielding the genotypes of 69 (XXY, triploid) or 92 (XXXY, quadraploid), or simply receiving two sets of chromosomes from the father. A complete mole is caused by one or two sperm combining with an egg which has no genetic information. The sperm then reduplicates, forming a complete set of 46 chromosomes. The sperm grows on its own but cannot develop into a fetus, resulting in only a clump of tissue inside the uterus. The incidence for this condition in North America and Europe is 1:1000 to 1:1500, in Asia and Latin America is 1:400