颈部透明度测试

定义

The nuchal translucency test measures the nuchal fold thickness. This is an area of tissue at the back of an unborn baby's neck. Measuring this thickness helps assess the risk for 唐氏综合症 and other genetic problems in the baby.

选择的名字

颈背的半透明 screening; NT; Nuchal fold test; Nuchal fold scan; Prenatal genetic screening; 唐氏综合症 - nuchal translucency

如何执行测试

Your health care provider uses 腹部超音波 或者一个 阴道超声 测量颈褶. All unborn babies have some fluid at the back of their neck. In a baby with 唐氏综合症 or other genetic disorders, there is more fluid than normal. This makes the space look thicker.

A blood test of the mother is also done. Together, these two tests will tell if the baby could have 唐氏综合症 或者一个nother genetic disorder.

如何准备考试

Having a full bladder will give the best 腹部超音波 picture. You may be asked to drink 2 to 3 glasses of liquid an hour before the test. DO NOT urinate before your ultrasound.

If a 阴道超声 is performed, your bladder should be empty.

考试的感觉如何

You may have some discomfort from pressure on your bladder during the ultrasound. The gel used during the test may feel slightly cold and wet. You will not feel the ultrasound waves.

为什么要进行测试

Your provider may advise this test to screen your baby for 唐氏综合症. Many pregnant women decide to have this test.

颈背的半透明 is usually done between 12 and 14 weeks of pregnancy. It can be done earlier in pregnancy than 羊膜穿刺术. Amniocentesis is another test that checks for birth defects.

正常的结果

A normal amount of fluid in the back of the neck during ultrasound means it is very unlikely your baby has 唐氏综合症 或者一个nother genetic disorder.

颈背的半透明 measurement increases with gestational age. This is the period between conception and birth. The higher the measurement compared to babies the same gestational age, the higher the risk is for certain genetic disorders.

A measurement of up to 3 mm is considered a low risk for genetic disorders. However, different clinics may use slightly different numbers based on their experience.

异常结果意味着什么

More fluid than normal in the back of the neck means there is a higher risk for 唐氏综合症, 称18三体综合症, 三倍体13, 特纳综合征, 或者先天性心脏病. But it does not tell for certain that the baby has 唐氏综合症 或者一个nother genetic disorder. A diagnostic test is required to find out if a serious genetic disorder is present.

The nuchal translucency test is a screening test. It does not screen for genetic problems in babies. It is helpful in deciding who may need further testing. An abnormal result would then require follow up of a diagnostic test such as an 羊膜穿刺术 or non-invasive prenatal test (NIPT).

风险

There are no known risks from ultrasound.

参考文献

American College of Obstetricians and Gynecologists website. NIPT summary of recommendations. www.服用抗.org/advocacy/policy-priorities/non-invasive-prenatal-testing/current-服用抗-guidance. 2023年6月7日访问.

Driscoll DA, Simpson JL. Genetic screening and diagnosis. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8日艾德. Philadelphia, PA: Elsevier; 2021:chap 10.

杜高夫L，瓦普纳RJ. Prenatal diagnosis of congenital disorders. In: Lockwood CJ, Copel JA, Dugoff L, et al, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 9日艾德. Philadelphia, PA: Elsevier; 2023:chap 30. 

沃尔什JM，达尔顿ME. 颈背的半透明. In: Copel JA, D'Alton ME, Feltovich H, et al, eds. Obstetric Imaging: Fetal Diagnosis and Care. 第二版. Philadelphia, PA: Elsevier; 2018:chap 45.