Usually, fetal NT is screened for Down syndrome by combining blood drawing. If NT is less than 2.5MM, combined with the blood test results, the risk of Down syndrome is relatively low.
A rough and simple estimation method is that when the measured value is less than 2.5mm, it is judged to be normal, and when the measured value is greater than or equal to 2.5mm, it is diagnosed that the transparent layer of the neck is thickened, its thickness increases, and the possibility of fetal abnormality increases.
I suggest you have a check-up to rule out the risk of Down syndrome.
I wish you the best of health!