The accuracy of such a forecast is also far from the ideal, but higher than the previous.
Abstinence method
An interesting modern method: for a girl to be born, parents must refrain from an intimate relationship longer, and in order to appear a boy — to make love more often. With prolonged abstinence in the body of men, special antibodies appear that reduce spermatozoa activities with Y chromosome. Therefore, after abstinence, a period of heyday of spermatozoa with the x chromosome occurs.