Non-invasive DNA test, sex chromosome bias is a chromosomal abnormality, which is uncommon in clinical practice. Non-invasive DNA test is to determine whether the genetic material of the fetus is normal or not by drawing blood, which can find out whether the chromosomes of the fetus are normal or not, and determine whether the fetus is developing abnormality or not. When this test is performed, if there is a small number of sex chromosomes, it means that there is an abnormal result, which is uncommon in the clinic, and the fetus may have abnormal development, and further amniocentesis is needed to clarify the situation. If the non-invasive DNA test appears to have low sex chromosomes, it is recommended to go to the hospital in a timely manner, to clarify the cause of the disease under the guidance of the doctor, and to take standardized methods of treatment to prevent adverse consequences.