Down’s screening is a mandatory test. Down’s syndrome is generally referred to as trisomy 21 or trisomy 18, which is when the fetus is divided in development with triploid chromosomes. If the development of this kind of child is seriously abnormal, his brain and limb development will have problems, so in the 4D ultrasound screening, it may find that the development of the fetus is abnormal, and at this time, we may abort the child, don’t want this child. But if the child has mild abnormalities in development, intellectual abnormalities or mild motor abnormalities, then when we do the ultrasound screening, the development of his organs are normal and cannot be seen. So if you don’t do the Down’s syndrome test or chromosome test, the child will be born different from a normal child, which will cause a huge burden to the family and society, and bring immense pain. Nowadays, we all talk about eugenics, in order to have a healthy child, it is still recommended to do Down’s syndrome screening.