Usually 4 weeks as a gestational age to describe the growth and development of the fetus in the body, at the end of the 4th week, the placenta and the body clitoris can be distinguished; at the end of the 8th week, the first human form, the head is large, the embryonic limbs appear, and the primitive heartbeat can be heard by ultrasound. At the end of the 12th week, the external genitalia have occurred, but only part of the fetus can distinguish the sex, and the limbs can be moved; at the end of the 16th week, the sex of the fetus can be determined from the external genitalia, so the sex of the fetus can be determined at the 19th week of pregnancy. However, according to national regulations, any non-medical identification of the sex of the fetus is prohibited, so doctors are not allowed to disclose the sex of the fetus at will.