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Cystic hygroma and increased nuchal translucency

Lynn L Simpson, MD
Section Editors
Deborah Levine, MD
Louise Wilkins-Haug, MD, PhD
Deputy Editor
Vanessa A Barss, MD, FACOG


A small, thin hypoechoic space in the posterior fetal neck is a common finding in normal first-trimester fetuses. In some fetuses, this space is enlarged due to a cystic hygroma or mesenchymal edema (called increased nuchal translucency). These fetuses are at increased risk for structural abnormalities and aneuploidy, particularly Down syndrome.

The diagnosis, clinical significance, and management of pregnancies complicated by a cystic hygroma or increased nuchal translucency will be reviewed here. Additional first-trimester markers and second-trimester ultrasound markers of aneuploidy are reviewed separately. (See "Sonographic findings associated with fetal aneuploidy".)


Anatomy and pathogenesis — The term nuchal translucency refers to the hypoechoic region located between the skin and soft tissues behind the cervical spine (image 1A). This hypoechoic space is presumed to represent mesenchymal edema and is often associated with distended jugular lymphatics [1,2]. A small but measurable amount of nuchal fluid can be identified in virtually all fetuses between the 10th and 14th week of gestation and is considered a normal finding if below a defined threshold (see 'Prenatal diagnosis' below). Above this threshold, the fetus is considered to have increased nuchal translucency.

The pathogenesis of nuchal edema is unknown, but is probably multifactorial and differs depending on the underlying fetal disorder [3,4]. For example, in trisomy 21 the collagen content of the dermis is abnormal; its hydrophilic properties may lead to the accumulation of subcutaneous fluid. In Turner syndrome, lymphatic dysplasia may lead to increased nuchal fluid, or narrowing of the aortic isthmus and widening of the ascending aorta may lead to overperfusion of the head and neck, thus contributing to the development of subcutaneous edema. In fetuses with abnormal nuchal lymphatic development, distension of the jugular venous sacs, accumulation of fluid in the nuchal region, and retrograde increases in venous pressure may occur. In fetuses with congenital heart disease, mutations in genes encoding for endothelium and involved in both cardiac and lymphatic development may contribute to increases in nuchal fluid [5-7].

Prenatal screening — Nuchal translucency is measured as part of first trimester and integrated screening tests for Down syndrome. (See "First-trimester combined test and integrated tests for screening for Down syndrome and trisomy 18".)

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Literature review current through: Nov 2017. | This topic last updated: Sep 26, 2017.
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