The best period for fetal DNA paternity testing. Fetal DNA paternity testing uses the free fetal DNA present in the maternal blood for identification. It can be used to determine the identity of the father or apply to determine the identity of the mother. So, when is the best time for fetal DNA paternity testing? First, it is necessary to ensure that the content of fetal free DNA in the maternal blood is high enough to ensure the accuracy of the test results. This content begins to gradually increase at 10 weeks of pregnancy, reaches a peak at 12 weeks of pregnancy, and remains stable thereafter. Therefore, fetal D is recommended after 12 weeks of gestation