The outer layer of the fertilised OVUM which attaches the ovum to the wall of the UTERUS (or womb) and supplies nutrition to the EMBRYO.
n. the tissue that forms the wall of the *blastocyst. At implantation it forms two layers, an inner cellular layer (cytotrophoblast), which does not invade maternal tissue and forms the outer surface of the *chorion; and an outer syncytial layer (syncytiotrophoblast, or plasmoditrophoblast), which erodes the maternal tissue and forms the chorionic *villi of the placenta. See also gestational trophoblastic disease.
(GTD) a group of disorders spanning the conditions of complete and partial molar pregnancies (see hydatidiform mole) through to the malignant conditions of invasive mole, *choriocarcinoma, and the very rare placental site trophoblastic tumour (PSTT). If there is any evidence of persistence of GTD, most commonly defined as a persistent elevation of *human chorionic gonadotrophin, the condition is described as *gestational trophoblastic neoplasia.... gestational trophoblastic disease
(GTN) a group of disorders characterized by persistence of *gestational trophoblastic disease, with abnormal placental development and very high levels of *human chorionic gonadotrophin (hCG). The chorionic villi are fluid-filled with vacuolation of the placenta and destruction of the normal stroma. GTN is rare in the UK, with a calculated incidence of 1/714 live births. It may develop after a molar pregnancy (see hydatidiform mole), a nonmolar pregnancy, or a live birth. The incidence after a live birth is estimated at 1/50,000. A malignant condition may develop (see choriocarcinoma) if the abnormal tissue is not completely removed and the risk of this is monitored by the fall in hCG levels. Choriocarcinoma complicates approximately 3% of complete moles, although in 50% of cases of choriocarcinoma there is no history of immediately preceding trophoblastic disease. It may also occur following a normal pregnancy. In the UK, there is an effective registration and treatment programme. The programme has achieved impressive results, with high cure (98–100%) and low chemotherapy (5–8%) rates.... gestational trophoblastic neoplasia
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