SHETTLES METHOD SUMMARY
Basically, men produce two types of sperms, the X (female) and Y (male). According to Dr. Shettles' studies the y-sperms are smaller, weaker, but faster than their siblings x-sperms, which are bigger, stronger, but slower.
Based on this fact, there are several things you can do to "favor" the conception of boys or girls:
(1) The most important aspect of all is timing of intercourse during the monthly cycle. The closer to ovulation you have sex, the better the chances to have a boy, because the y-sperms are faster and tend to get to the egg first. If you have sex 3 days or more before ovulation, the better your chances to conceive a girl, because the weaker y-sperms tend to die sooner and the x-sperms will be available in greater quantity whenever the egg is released. On the other hand, having sex from 2 days before ovulation, through a few days after ovulation, is better for conceiving a boy. Around the 2-day point -- 48 hours before ovulation -- seems to be the 50/50 mark.
(2) The pH of the women's tract is also very important. A more acidic environment favors girls, since it will kill the weaker y-sperms first, leaving a greater quantity of x-sperms available to fertilize the egg. On the other hand, a more alkaline environment favors boys. Shettles recommends a douche of water and vinegar (acid) immediately before intercourse to favor a girl; a douche of water and baking soda (alkaline) will help for a boy