As the size of the average family decreases throughout the developed world, the number of people looking for ways to influence the genders of their children has gone up. While many people rely on technology to make sure they bring home the baby boy or a baby girl they’ve been hoping for, others are turning to more traditional methods of gender selection to achieve their goals. Is there really anything you can do to tip the odds of conceiving a child of the desired gender?
Dr. Landrum Shettles was one of the first to claim that couples could influence whether they conceived boys or girls through their actions during sexual activity. In 1971, he co-authored a book called How to Choose the Sex of Your Baby, which gave several suggestions regarding what times and positions were best depending on whether you were trying for a boy or a girl.
As a reminder of what it takes to make a baby, men produce two kinds of sperm: ones with X chromosomes and ones with Y chromosomes. Women usually release an egg about halfway through the month, on day 14 of their cycle, although there is a wide range of variance. Upon conception, the sperm joins with the egg, which always carries an X chromosome, to create an embryo. If an X sperm fertilizes the egg, the embryo will have two X chromosomes, and normally develops into a girl. If an Y sperm fertilizes the egg, the embryo usually develops into a boy.
Since the type of sperm is how gender is determined, it makes sense that taking advantage of the differences between the two types would be useful in natural gender selection. According to Dr. Shettles, the X sperm are fast and weak, while the Y sperm are slow and hardy. Shettles listed several factors which would help protect male sperm, including timing sex for the days immediately following ovulation, using positions which favor deeper penetration, and promotion of female orgasms prior to ejaculation.
From the point at which an egg is released and for one to two days after, the vaginal pH switches from acidic to alkaline, which is less damaging to male sperm. The mucus covering the cervix, where sperm enter the womb, also thins at this time, making it easier for the Y sperm to swim past their slower brothers. How you have sex can also play a role. Rear entry positions such as “doggy style” will deposit sperm closer to the cervix. Studies have also shown that when women have an orgasm prior to her partner’s ejaculation, resulting internal muscle spasms can suck up more sperm. Both factors would give an edge to Y sperm.
Professionals who use the Shettles method claim that couples can expect a success rate of 80 to 85 percent when trying to conceive a boy. The odds of having a girl, are slightly lower, at between 75 to 80 percent. While these are fairly good results, most genetics experts recommend working with a fertility clinic if you would prefer a boy or a girl based on a specific medical reason, such as a known risk of the child having a sex-linked condition such as hemophilia.