Which is the most accurate method to identify male and female

The following methods can be used: blood test to determine the sex of the fetus maternal DNA blood test, amniocentesis, ultrasound. \r\n1, blood test to determine the sex of the fetus maternal DNA blood test: genetic engineering technology can be used to take the mother's vein blood, to determine the sex of the fetus. There is no risk to the fetus and the mother, and because of the report from the blood DNA laboratory, the accuracy of the identification can now reach up to 98%, through the chromosomes to make gender inferences. Especially in the case of male babies, the reaction is positive. The baby is tested after 8 weeks and the result is available in about 3 days. \r\n2, amniocentesis: mainly to diagnose whether the fetus has chromosomal aspects or defects in the neural tube, usually carried out in 16 to 20 weeks of pregnancy. Since the chromosomes of the fetus can be known, the sex of the fetus can also be known. The accuracy can reach 99%, but there is a 1% chance of miscarriage. \r\n3, ultrasound, four-dimensional ultrasound, the accuracy is not as high as the first two.