The Shettles Method of gender selection is a natural method devised by Landrum B. Shettles, M.D., a pioneer in in vitro fertilization research at Columbia University. He studied gender selection and published his findings in a 1970s article called “Factors influencing sex ratios” in the International Journal of Gynaecology and Obstetrics.
His findings led to writing a book called How to Choose the Sex of Your Baby, which is still popular today.
The method is based on Dr. Shettles’ findings that the sperm bearing the Y chromosome, which result in a baby being a boy, are lighter and faster swimmers than the sperm bearing the X chromosome, which are slower and weigh more, but are more resistant to the acidic cervical environment. The X-bearing sperm live longer than the Y-bearing sperm.
To achieve the baby of the desired sex, the couple must track the woman’s ovulation, so that the normal time of ovulation can be pinponted. This can, of course, be hard to do if a woman’s cycle is irregular. The method also assumes that a woman’s vaginal environment is acidic and then becomes slightly more alkaline closer to ovulation.
Once the couple has pinpointed the time of ovulation, they should time sex in order to get the child of the desired sex.
The Shettles Method recommends:
- To conceive a boy, a couple should time sex on the day of ovulation or as close to ovulation as possible, since the Y sperm are faster and will reach the egg sooner than the slower X sperm. The Shettles Method also suggests deep penetration with positions such as rear entry intercourse that will allow the sperm to be deposited closer tot he cervix with less distance to travel.
- To conceive a girl, the Shettles Method advises timing sex for two to three days before ovulation and avoid sex just before ovulation, the day of ovulation and two days after ovulation. This way, the hardier X-bearing sperm have the advantage of already being in position to fertilize the egg. Also recommended is more shallow penetration during sex in a position such as the missionary position. This deposits sperm away from the cervix and gives X-bearing sperm the advantage since they live longer but move more slowly. In addition, the method recommends that women avoid orgasm if they are trying to conceive a girl in order to keep the vaginal environment more acidic, which is better for the X sperm.