I have heard something about how the sex depends on the pH of the woman's cervix at time of conception. Certain pH's are better for the boy sperms and certain pH's are better for the girl sperms. I don't know how true this is. But they have those boy and girl diets you can go on that is suppose to change the pH in your cervix to help you have to sex you are wanting.
Trying to determine the sex any way other than seeing if it is boy or girl gets me.