Complete hydatidiform mole

A complete hydatidiform mole (CHM), also known as a complete molar pregnancy, is an abnormal form of pregnancy in which no embryo develops and the placental tissue grows into a mass of cyst-like structures resembling a cluster of grapes. It is classified as a type of gestational trophoblastic disease (GTD). In a complete mole, all genetic material comes from the father (androgenetic origin), most commonly arising when a single sperm fertilizes an empty egg and then duplicates its chromosomes (46,XX), or less frequently when two sperm fertilize an empty egg (46,XX or 46,XY). The condition affects the reproductive system and, if not properly managed, can lead to serious complications including persistent gestational trophoblastic neoplasia (GTN), a malignant condition. Key symptoms include abnormal vaginal bleeding during the first trimester, a uterus that is larger than expected for gestational age, markedly elevated levels of human chorionic gonadotropin (hCG), absence of fetal heart tones, and passage of grape-like vesicles. Patients may also experience severe nausea and vomiting (hyperemesis gravidarum), preeclampsia occurring unusually early in pregnancy, ovarian theca lutein cysts, and rarely hyperthyroidism. Ultrasound typically reveals a characteristic "snowstorm" pattern with no identifiable fetus. Treatment involves uterine evacuation by suction curettage, which is the standard first-line approach. Following evacuation, serial monitoring of serum hCG levels is essential to ensure complete resolution and to detect any progression to gestational trophoblastic neoplasia, which occurs in approximately 15–20% of complete molar pregnancies. If hCG levels plateau or rise after evacuation, chemotherapy is indicated. Most patients with GTN following a complete mole respond well to single-agent chemotherapy (methotrexate or actinomycin D) and have excellent cure rates. Reliable contraception is recommended during the hCG monitoring period, which typically lasts 6–12 months. Rare familial forms of recurrent hydatidiform mole exist, associated with biparental (rather than androgenetic) origin, caused by mutations in genes such as NLRP7 or KHDC3L, inherited in an autosomal recessive pattern.

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