Mention is made in ब्रह्माण्ड पुराण , Chapter 48, that the semen introduced into the womb of the woman by the man at the time of coition, will get mixed with the blood in the womb, and that the issue will be male, female or eunuch according to the proportion of the mixture. In the mixture of semen and blood, if blood exceeds semen the issue will be female and if semen exceeds, it will be male child and if both are equal the child will be a eunuch.