People have been asking these questions for thousands of years but no one has yet discovered exactly why a mother has a boy or a girl. It has been known since 1959 that if a y-chromosome sperm fertilises the egg, the baby will be a boy. But nobody knows exactly HOW the selection happens at the time of fertilisation.
This site discusses the theory that the sex of a baby is determined, not solely by chance, but by the nature of the mother. There may be a natural selection process that alters the probability of a mother having a boy or girl, depending on some of her characteristics. Some people think this sounds bizarre. But there is plenty of evidence to suggest that the determination of the sex of the infant is not entirely random. Something else besides chance may have an influence: the mother’s level of testosterone.
This potent chemical hormone has important effects on human bodies. Even tiny quantities can change the physical and psychological characteristics of both men and women. It also affects the way people behave. Since testosterone influences people’s behaviour in known ways, it is possible to get an idea of a person’s testosterone levels by asking them about some of their characteristics. Thus it is quite feasible that a psychological test will indicate whether a mother will have a boy or a girl.
The ongoing scientific research tries to explain phenomena such as why, after war, more boys are born than usual or why, today, fewer boys are being born throughout the western world. Unlike potions, positions or superstitions, this site describes phenomena that have a scientific basis.
The site contains information about a book which describes the research - as well as an online test that you can do that will tell you what your chances are of conceiving a boy or a girl.