As part of today’s medical advancement, certain soft markers can be used to diagnose whether you’re unborn has a genetic disorder. The nuchal fold thickness is a soft marker studied during a prenatal scan to check for chromosomal abnormalities, such as Down syndrome.

What is the Nuchal Fold?

The Nuchal fold is an ordinary fold of skin present at the back of a fetal neck.

Baby in uterus
Image courtesy: whattoexpect

What Is Nuchal Fold Thickness?

Nuchal fold thickness is the distance between the outer edge of the occipital bone ((bone which forms the back and base of the skull and encircles the spinal cord) and the outer edge of the midline skin.

This measurement is performed during the prenatal ultrasound scan at the end of the second trimester.

Is Nuchal Fold And Nuchal Translucency The Same?

Many confuse these two terms, but they both are distinctly different.
Nuchal translucency is a collection of transparent tissue under the skin behind the neck of the fetus.

Nuchal fold and nuchal translucency are the referring soft markers for identifying any chromosomal abnormalities in your baby. With this, research concludes a small correlation between the nuchal fold and nuchal translucency with that of Down syndrome.

While both are independent factors that determine Down syndrome risk, nuchal fold measurement is more effective when combined with sequential contingent screening.

What Is The Normal Nuchal Translucency Range?

It is usually common for a fetus to have transparent tissues in the womb. But it is equally important to map its measurement against the gestation age to indicate any possibilities of genetic abnormalities.

Nuchal translucency measurement is studied during your first-trimester Nuchal Translucency (NT) scan.

Normal range of NT

The normal NT range depends on when you undergo your first-trimester screening. The correct time to have an NT scan is between 11 and 13 weeks of pregnancy  The last day you can have your NT scan is when you are 13weeks and 6days pregnant. After this period, most fluid-like tissue is absorbed by the baby’s developing body.

During the 12th or 13th week of pregnancy, a normal nuchal translucency range should be under 2mm. Measurements above this are considered as an abnormal NT

What Is The Normal Range Of Nuchal Fold Thickness?

Same as nuchal translucency, the nuchal fold thickness is also expected to be between a certain range to screen for chromosomal abnormalities.

Normal Nuchal Fold Range

Nuchal fold measurement is studied during your second-trimester scan, called an Anomaly scan. The right time to get your anomaly scan is between 14 and 24 weeks of gestation. And nuchal fold thickness >6mm is considered abnormal during the second scan.

The thickness of the nuchal fold is expected to fall under a certain level during your first trimester Nuchal Translucency scan, and the abnormal measurement of the same would indicate a genetic disorder.

What Causes Abnormal Nuchal Fold Thickness?

The increased nuchal fold thickness might be the cause of lymphatic obstruction.

Lymphatic obstruction blocks the lymph vessels that drain fluid from tissues throughout the body and allow immune cells to travel where they are needed.

It is important to note that some normal healthy babies also have increased nuchal fold thickness.

Some reasons for abnormal nuchal fold thickness in healthy babies:

     1. Position of the baby:

Your baby’s position during the scan can sometimes make the nuchal fold appear thicker than usual.

     2. Nuchal fold thickness variation:

Each baby is unique. All the babies don’t need to have the regular nuchal fold thickness. It is also said that male babies have thicker nuchal folds than females.

    3. Measurement error:

Sometimes, it is hard to study the exact thickness of a nuchal fold in an ultrasound scan.

Reasons for thick nuchal fold in healthy babies
Position of the baby
The nuchal size differs for each baby
Wrong measurement

What are the health issues related to abnormal Nuchal Fold thickness?

Increased nuchal fold thickness is a reliable soft marker for chromosomal abnormalities, especially Down Syndrome.

However, it is also to be noted that the baby can have the conventional chromosome karyotype but can be exposed to other threats like,

  • Fetal malformations
  • Congenital heart defect
  • Intrauterine death
  • Miscarriage

What if the Third-trimester scan shows abnormal Nuchal fold thickness?

As discussed, even some normal babies have an enlarged nuchal fold thickness, so you would be suggested to have confirmatory tests for chromosomal defects.
How can abnormal nuchal fold thickness be treated?


Other than chromosomal abnormalities, the potential threats can be challenging to diagnose before birth. Some threats can be mild and treated with medicine, and some might need surgery.

If your baby is confirmed to carry a chromosomal genetic disorder, it is impossible to give any treatment in the form of medicines. There are specific therapies and treatments offered to these babies after birth.
You can discuss this with your doctor and genetic counsellors to receive detailed guidance.

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