The growth of hair on the belly during pregnancy cannot determine whether it is a boy or a girl. Hair on the stomach during pregnancy may be caused by an imbalance of estrogen secretion or elevated androgen, and has nothing to do with the sex of the fetus, which is decided the moment the sperm and the egg combine. In folklore, there is a saying that the hair on the belly of a pregnant woman gives birth to a boy, and this saying has no scientific basis. To determine the sex of the fetus, you can only use ultrasonography and genetic testing, but in our country, the law prohibits the identification of the sex of the fetus for non-medical purposes, and pregnant women are not allowed to ask the doctor about the sex of the fetus. During pregnancy, the growth of sweat hair is a normal physiological phenomenon, and can be restored to normal after delivery.