If a woman is pregnant and is unsure who the father of her baby is, a paternity test can be performed to determine this. In general, paternity testing can be done by collecting chorionic villi as early as 8 weeks after conception, but in the early stages of the embryo at 8 weeks of pregnancy, there are certain risks associated with the collection of chorionic villi. In order to ensure the safety of the pregnant woman and the fetus, most of the tests are carried out after 11 weeks, which is relatively safer and requires a medical examination followed by a puncture in a qualified specialized hospital. In the 11th week of pregnancy, fetal chorionic villi are collected under the guidance of an obstetrician and an ultrasound. After the collection of chorionic villi, rest should be paid attention to, and oral medication to protect the fetus can be given appropriately. In addition, after 14 weeks of pregnancy, amniotic fluid specimen is extracted by amniocentesis, and then DNA testing is performed. After 14 weeks, the development of the fetus enters a stable period, and the extraction of a small amount of amniotic fluid will not affect its normal growth and development, so the impact on the fetus as well as the mother at about 14 weeks is relatively small, and relatively more safe and reliable.