Birth Definitions

Nuchal Fold Definition

The nuchal fold is a ridge of skin that runs along the back of the neck. When it comes to pregnancy, the term “nuchal fold” refers to a thickened area of skin on the back of the neck of a fetus. Also sometimes referred to as the nuchal ligament, this structure is a fold of skin that extends from the back of the neck down to the base of the spine. It helps to support the head and neck during pregnancy and childbirth.

Nuchal Fold was first described in the medical literature in 1968 by Smith and colleagues as a thickening of the skin at the back of the neck in hydrocephalus patients. The term “nuchal” comes from the Latin word for “neck.” The nuchal fold is a normal finding in early fetal development and is typically seen on ultrasound images of the fetus at 10-14 weeks gestation.

A thickened nuchal fold is associated with an increased risk of certain chromosomal abnormalities such as Down syndrome, and birth defects such as anencephaly and spina bifida. It is also associated with an increased risk of stillbirth and neonatal death. The nuchal fold is measured to assess the risk of these abnormalities. It is however just one of several markers used to assess the risk of chromosomal abnormalities in pregnancy. Other markers include the mother’s age, the level of fetal AFP, and the presence of other ultrasound abnormalities.

Outside the birthing world, the term “nuchal fold” is also used to describe the skin thickening at the back of the neck in adults. This thickening can be caused by various conditions, such as obesity or a goiter.

Nuchal Fold Measurement

The nuchal fold can be measured using a variety of methods, including inner pelvic border to outer shoulder (IPOB-OS) or eternal occipital protuberance to outer shoulder (EOP-OS). The use of the nuchal fold measurement to screen for chromosomal abnormalities has been found to be most accurate when performed between 18 to 22 weeks of gestation.

Nuchal fold measurements are not perfect, and some babies with abnormal nuchal folds will not have chromosomal abnormalities. Similarly, some babies with chromosomal abnormalities will have normal nuchal folds. The use of multiple screening tests, including nuchal fold measurement, can help to improve the accuracy of prenatal diagnosis.

This image shows how often the term ‘Nuchal Fold’ is used in relation to other, similar birth terms:

Other Related Terms

Other terms related to nuchal fold include:

Congenital heart defects: Congenital heart defects are conditions that affect the structure of the heart.

Stillbirth: Stillbirth is defined as fetal death after 20 weeks of gestation.

Neonatal death: Neonatal death is defined as death within 28 days of life.

Nuchal translucency: This is the name for the clear space behind the neck that can be seen on an ultrasound.

Nuchal cord: This refers to the umbilical cord being wrapped around the neck of the fetus.

Cervical length: This is the length of the cervix, which is the neck of the uterus. Measuring the cervical length can also help to assess the risk of chromosomal abnormalities.

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