The critical risk of Down’s syndrome can be caused by the advanced age of the pregnant woman, or by fetal chromosomal abnormalities and other causes.
Down’s syndrome screening is one of the screening tests, it is through the examination of maternal serum concentrations of alpha fetoprotein, chorionic gonadotropin and free estriol, and then combined with the pregnant woman’s gestational week and age to comprehensively assess the risk of chromosomal trisomy and neural tube malformation.
A critical risk for Down’s test results may be due to a high gestational age of the pregnant woman, such as greater than 35 weeks of age, which may affect the calculation of the results and result in a critical risk.
In addition, a critical risk in Down’s screening may also be caused by fetal chromosomal abnormalities, which require further non-invasive DNA testing or amniocentesis for definitive diagnosis.