Noninvasive DNA testing is mandatory for twin pregnancies that show no abnormalities. Non-invasive DNA testing is used to extract fetal DNA fragments through the vein blood of pregnant women, combined with bioinformatic analysis to detect the presence of chromosomal disorders in the fetus. At present, non-invasive DNA testing is mainly applicable to single fetus. The accuracy of noninvasive DNA testing for twin fetuses is closely related to the concentration of fetal free DNA, but the chromosomal karyotypes of dizygotic twins are often inconsistent. If the amount of free DNA of the abnormal fetus is lower than the threshold value and the amount of DNA of the normal fetus is sufficiently high, the test result may indicate a low risk due to the normal fetus masking the abnormal fetus when the total amount of free DNA reaches the minimum value required for the test, resulting in a false-negative result. Therefore, it is recommended that pregnant women inform their physicians in advance and follow their doctor’s instructions to complete the relevant prenatal tests.