After pregnancy, you can know whether the fetus is a boy or a girl through blood tests, ultrasound and amniocentesis, but non-medical fetal sex determination is now prohibited. 1. Blood test. When you are 2-3 months pregnant, you can go to the hospital to have a blood test to determine the DNA of the fetus and know the chromosome condition, so as to determine the sex of the fetus. 2. Ultrasound. After 16 weeks of pregnancy, the external genitalia of the fetus has been fully developed, and you can know the sex of the fetus through ultrasound to see the genital organs, generally as long as the position of the fetus is good, the accuracy is relatively high. 3. Amniocentesis. At 16-20 weeks of pregnancy, amniocentesis can be used to determine whether the fetus has chromosomal or neural tube defects, and the sex of the fetus can also be known through the fetal chromosomes. After pregnancy, you can generally know whether the fetus is a boy or a girl through the above methods, but at present, there are clear provisions of the regular hospitals are prohibited to do non-medical fetal sex identification, as long as the baby is healthy, male and female babies are the same.