The birth of a son or daughter depends on whether the man’s sperm has an X or a Y chromosome. In human germ cells, there are 23 pairs of chromosomes, of which 22 pairs are autosomes and 1 pair is a sex chromosome. Females have XX sex chromosomes, while males have XY sex chromosomes.When the germ cells are undergoing meiosis, females produce only one type of egg, which is X. The male produces a sperm that is X, while the female produces a sperm that is X. The sperm produced by the male may be of type X or Y. If the sperm contains X chromosome, the sperm may be either X or Y. If a sperm with an X chromosome combines with an egg, the fertilized egg is type XX and develops into a female fetus. If a sperm with a Y chromosome combines with an egg, the fertilized egg is XY and develops into a male fetus. So from the time the fertilized egg is formed, the sex of the baby is already predetermined. It is important to note that the sperm-egg combination is randomized so that the general balance of the human sex ratio can be maintained. Having a boy or girl is the same, so be at peace with yourself.