Is four-dimensional ultrasound the same as Down's screening?

Down's screening is divided into early Down's screening and mid-term Down's screening, which is to check whether the baby is Down's child, that is, the risk assessment of the baby suffering from Down's child. Down's screening accuracy is not high, only 60% to 70%, so it is necessary to do nt examination. Early screening, mid-term Down's screening to improve the screening rate of Down's children, Down's screening is to check whether the baby is dementia. Four-dimensional color Doppler ultrasound, generally recommended 20 weeks to 26 weeks of pregnancy to do, mainly to check the baby's various parts of the growth of abnormalities. Four-dimensional color Doppler ultrasound is a large row of abnormalities, with Down's screening is not the same. Four-dimensional color Doppler ultrasound is a B-ultrasound examination, Down's screening is a blood test.