Because some genetic diseases are closely related to sex, they are called X-linked genetic diseases. Letting boys and girls decide for themselves is not a myth. It is known that the birth of a boy or a girl is determined by the nature of the sperm. There are two kinds of sperm, one is X sperm and the other is Y sperm. The gender of a child may depend on whether the fertilized sperm is an X or Y sperm. If the sperm and egg are only X, then the sperm and egg will give birth to a girl; if the sperm and egg of Y will give birth to a boy. Through extensive research on the effects of pregnancy on female fertilization, scientists have discovered that many natural factors can have subtle effects on the binding of X sperm during conception. Typically, these factors will continue to act randomly, causing the ratio of women to boys to girls to become pregnant to be approximately 50:50