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Human chorionic gonadotropin: Testing in pregnancy and gestational trophoblastic disease and causes of low persistent levels

Barbara Goff, MD
Section Editor
Barbara Goff, MD
Deputy Editor
Sandy J Falk, MD, FACOG


Human chorionic gonadotropin (hCG) is produced by trophoblast, a layer of tissue on the outside of the blastocyst that provides the embryo with nutrients and later forms part of the placenta and the fetal membranes. Laboratory tests for hCG are almost 100 percent sensitive and specific for diagnosis of the trophoblast-related conditions, ie, pregnancy and the gestational trophoblastic diseases. Rarely, very low levels of hCG are detected in the absence of one of these conditions. Understanding the complexity of hCG molecules and the nuances of hCG testing is critical to managing these patients. (See "Placental development and physiology", section on 'Implantation and invasion'.)

Basic issues related to hCG testing will be reviewed in this topic. The clinical use of this test in the follow-up of women with gestational trophoblastic disease is discussed separately:

(See "Hydatidiform mole: Epidemiology, clinical features, and diagnosis".)

(See "Initial management of low-risk gestational trophoblastic neoplasia".)

(See "Hydatidiform mole: Management".)

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Literature review current through: Nov 2017. | This topic last updated: Apr 27, 2016.
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