The idea behind the Shettles Method of sex selection is based on the fact that the X and Y-chromosome carrying sperm have different characteristics and that under different circumstances either X- or Y-chromosome-carrying sperm will be more likely to fertilize the egg. It is a child conception idea that is reputed to help determine a baby’s gender developed by Landrum B. Shettles in the 1960s and was publicized in the book How To Choose the Sex of Your Baby, co-authored by Dr. Shettles and David Rorvik.(wikipedia)
According to Dr. Shettles, the sperm that carry the Y-chromosome are the "boy" sperms, while the ones that carry the X-chromosome are the "girl" sperms. The Y sperm are faster, smaller, more agile but they do not last as long as the "girl" sperm. The X sperm are bigger and move quite slowly. In addition to their overall speed, they have different preferences in terms of the acidity of the vagina and cervix. A Y-chromosome sperm does better in an alkaline environment while the X-chromosome sperm prefer an acidic environment as it can withstand the acidic cervical environment before fertile cervical fluid is produced.
Now that we have established the differences between the sperm that carry different chromosomes, it is important to understand how these differences can be used for natural gender selection according to Shettles Method. Once you have this information, you can begin trying to conceive a child that will be a specific gender.
If you want to have a boy,
o Time your intercourse as closely to ovulation as possible since these sperm do not live long. This gives the Y-chromosome sperm time to reach the egg before the X-chromosome sperm do, increasing the chances that you will have a boy.
o Sexual positions that allow deep penetration are preferred. Shettles Method suggests rear-entry or “doggy-style”. The sperm will be deposited closer to the cervix where cervical fluid is most friendly to Y-chromosome sperm and it is more likely to survive since there is less distance to travel
o Women to have orgasm first or at the same time. Dr Shettles suggests this will increase the alkaline secretions in the vagina that are favourable to Y-chromosome sperm
If you want to have a girl,
o Time intercourse a 2-3 days before expected ovulation since they live longer. This gives the X-chromosome sperm plenty of time to reach the egg. By the time you ovulate, the Y-chromosome sperm will have already died off, leaving only the X sperm behind. They will have the time needed to travel up through the cervix to reach the egg and fertilize it
o Sexual positions with shallow penetration are preferred. Shettles Method suggests “missionary position”, any position that will deposit the sperm away from cervix, exposing to acidic condition first, killing off Y-chromosome sperm and have time to fertilize the egg since it lasts longer
o Women to avoid orgasm. Dr. Shettles suggests it makes vaginal environment more acidic and is favourable to X-chromosome sperm
Shettles Method reviews are mixed as many woman claims that his method worked for them. Statistically, it has shown that it is 75 – 90 percent effective. Others may have not agreed since it shown no bearing on whether a boy or a girl is conceived. Being said so, there are more comprehensive natural methods that are known to be true, tried out and combine with, that may increase the chances in conceiving a boy or a girl.