The Scientific Principles of Conceiving a Boy and a Girl Conceiving a boy and a girl has always been a topic of concern, and now science can explain the principles behind this phenomenon. The following will explain the scientific explanation of the principles of male and female birth from four aspects: heredity, germ cells, hormones and environment. Genetics: The birth of a boy or a girl is primarily related to the genes of the parents. Among the 23 pairs of chromosomes in humans, the 23rd pair determines the gender of the child. The mother\’s 23 pairs of chromosomes are XX and the father\’s are XY. If the sperm carries an