NT Ultrasound 

A screening test, which is recommended at weeks 11 to 14 of the pregnancy by a gynecologist or obstetrician, is NT ultrasound that evaluates white areas on the back of the fetal neck.
In this ultrasound, first, fluid aggregation in the back of the neck will be evaluated. Then, all organs of the fetus will be measured and evaluated for chromosomal abnormality of Down syndrome disease.
In case of any inconsistency with normal criteria, necessary measures and complementary tests should be performed.

Doctors recommendation

Doctors recommendation that NT ultrasound is very helpful in the following cases:
Pregnancy at ages above 35
History of having children with congenital anomalies
History of congenital anomaly in the immediate family

In addition to the organs and thickness of the back of the neck, fetal nasal bone will also be evaluated. That is because the measurement of the nasal bones and its angle with the frontal bone has a diagnostic value at any gestational age, and is recommended in the second quarter of pregnancy.

In should be noted that the accuracy of ultrasounography in the diagnosis of disorders is 75% which increases to 85% through running a blood test.