The Mid-Ton’s test consists of four items: blood chorionic gonadotropin, blood free estriol, blood alpha-fetoprotein, and blood inhibin A, which are used to calculate the risk value.
Mid-pregnancy screening for Down syndrome is mainly performed by blood sampling, which does not require fasting, and the concentrations of serum chorionic gonadotropin, free estriol, alpha-fetoprotein, and inhibin are measured to determine the risk of chromosomal abnormalities, such as Down syndrome, trisomy 18, and trisomy 13, in the fetus.
Mid-pregnancy Down syndrome screening results are usually reported only as a risk value, with a normal result being low risk. A critical or high risk result indicates that the fetus may have chromosomal abnormalities such as Down syndrome and some genetic syndromes that require further screening.