Hydatidiform moleMolar pregnancy is an abnormal form of pregnancy, wherein a non-viable, fertilized egg implants in the uterus, and thereby converting normal pregnancy processes into pathological ones.
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Molar pregnancy is an abnormal form of pregnancy, wherein a non-viable, fertilized egg implants in the uterus, and thereby converting normal pregnancy processes into pathological ones. It's characterized by the presence of a hydatidiform mole (or hydatid mole, mola hytadidosa). Molar pregnancies are categorized into partial and complete moles; complete moles have no identifiable embryonic or fetal tissues and arise when an empty egg with no nucleus is fertilized by a normal sperm; in contrast, a partial mole occurs when a normal egg is fertilized by two spermatozoa. Hydatidiform moles may develop into choriocarcinoma, a form of cancer.
The etymology is derived from hydatis (Greek "a drop of water"), referring to the watery contents of the cysts, and mole (from Latin mola = millstone/false conception). The term, however, comes from the similar appearance of the cyst to a hydatid cyst in an Echinococcosis. A hydatidiform mole conception is sometimes referred to colloquially as an early (natural) "missed abortion."
In most complete moles, all nuclear genes are inherited from the father only (androgenesis). In approximately 80% of these androgenetic moles, the most probable mechanism is that an empty egg is fertilized by a single sperm, followed by a duplication of all chromosomes/genes (a process called "endoreduplication"). In approximately 20% of complete moles the most probable mechanism is that an empty egg is fertilised by two sperms. In both cases, the moles are diploid (i.e. there are two copies of every chromosome). In all these cases, the mitochondrial genes are inherited from the mother, as usual.
Molar pregnancies usually present with painless vaginal bleeding in the fourth to fifth month of pregnancy. The uterus may be larger than expected, or the ovaries may be enlarged. There may also be more vomiting than would be expected (hyperemesis). Sometimes there is an increase in blood pressure along with protein in the urine. Blood tests will show very high levels of human chorionic gonadotropin or (hCG).
Hydatidiform moles should be treated by evacuating the uterus by uterine suction or by surgical currettage as soon as possible after diagnosis, in order to avoid the risks of choriocarcinoma. Patients are followed up until their serum (hCG) level has fallen to an undetectable level. Invasive or metastatic moles (cancer) may require chemotherapy and often respond well to methotrexate. The response to treatment is nearly 100%. Patients are advised not to conceive for one year after a molar pregnancy. The chances of having another molar pregnancy are approximately 1%.
More than 80% of hydatidiform moles are benign (not cancer). The outcome after treatment is usually excellent. Close follow-up is essential. Highly effective means of contraception (condoms and the pill) are recommended to avoid pregnancy for at least 6 to 12 months.
