What is the normal value of nuchal translucency (NT)?

Nuchal translucency (NT) screening is a prenatal test performed around week 12 of pregnancy. It uses ultrasound to measure the thickness of the fluid-filled space at the back of the fetal neck—the nuchal translucency. This measurement helps assess the risk of Down syndrome (trisomy 21) and other chromosomal abnormalities. In addition to ultrasound, NT screening is often combined with non-invasive prenatal testing (NIPT) and/or amniocentesis for more comprehensive evaluation. So, what is the normal NT value?

What is the normal NT value?

The normal NT value is typically ≤2.5 mm (not cm—this appears to be a typographical error in the original text). The scan is usually performed around gestational week 12 and is an essential component of routine prenatal care. Fasting is not required, nor is bladder filling prior to the examination. If the measured NT thickness exceeds 3.0 mm, it may indicate an increased risk of chromosomal abnormalities, warranting further diagnostic testing—such as amniocentesis or cell-free DNA analysis—to confirm or rule out such conditions.

An elevated NT measurement may suggest an increased risk of Down syndrome or other chromosomal disorders. It may also be associated with fetal lymphatic malformations such as cystic hygroma—a sign of abnormal fetal development. Generally, the higher the NT value, the greater the clinical concern. Further diagnostic evaluation at a hospital is necessary to exclude underlying abnormalities before deciding whether to continue the pregnancy. If the NT value is markedly elevated, termination of pregnancy may be recommended following thorough counseling and evaluation by a qualified obstetrician or genetic counselor.

Pregnant women should attend regular antenatal check-ups at a healthcare facility. Additionally, they should avoid exposure to ionizing radiation and other environmental hazards to minimize potential adverse effects on fetal development. We hope this information is helpful to you.