There are a lot of theories about natural gender selection. You've probably heard conflicting opinions on different ways to choose your baby's sex. Timing intercourse during your cycle is a theory that was once widely believed to be true, but has now fallen out of favor. Why has it fallen out of favor, and could there be any validity to it? This article will cover some possibilities.
What Dr. Shettles Thought
Dr. Shettles is an important name because of his book, Choose the Gender of Your Baby. Dr. Shettles has passed away now, but he did a lot of work involving gender selection and developed strong theories. Many of those theories are thought to be incorrect now... or at least what he thought made them correct is thought to be incorrect at this point.
For example, he thought that Y sperm (which are the sperm that create boys) could swim faster than X sperm (which are the sperm that create girls). He advised his patients to use timing to give those (what he thought were faster boy sperm) the best chance of reaching the egg quickly. Or if you wanted a girl, then you would make sure that there was a delay in when you timed your baby-making sex so that by the time the egg was released, the slower egg sperm were able to catch up and the Y sperm had already gotten there and had been exhausted and were gone.
That was Dr. Shettles' theory. We know now (or scientists think now) that that's probably not true. The speed of swimming theory is not true and the X and Y sperm probably swim at about the same speed. They're probably about the same size even though X sperm were thought to be bigger.
The concept of timing intercourse and a lot of the things that Dr. Shettles taught fell out of favor and are still out of favor in the gender selection world. Many think that hormones have a big influence... and hormones could explain the timing issues that Dr. Shettles observed, however.
Hormones and How They Line Up
Remember, what Dr. Shettles observed was: when you have baby-making sex closer to the time of ovulation, you're more likely to get a boy. And if you have intercourse farther away from the time of ovulation, you're more likely to get a girl. Dr. Shettles thought this was true because of the speed of the different sperm. But now, researchers think it might be because of the mother's hormonal profile at those different times in the cycle.
For instance, right around ovulation is when a woman's testosterone is the highest and her FSH hormone and her LH hormones are a little bit lower. It's thought that higher testosterone and higher estrogen levels favor the conception of sons. Those hormones being lower and the FSH and the LH hormones being higher favors girls.
How does this work in the menstrual cycle? When a woman's body gets close to ovulation, her estrogen levels begin to go up. They reach a peak and then her estrogen levels start to fall. When the estrogen levels start to fall, the LH and FSH surge and peak. This happens just a couple of days, even hours (36-48 hours or so) before ovulation.
Then those levels start to fall again and again estrogen is the more dominant hormone. Testosterone also rises at this point (which also helps explain why a woman who is right at ovulation is more interested in lovemaking). This means that at the time of ovulation the testosterone and estrogen levels are higher.
If you look at the timing that Dr. Shettles observed (which, remember, was if you have baby-making sex a few days before ovulation, you're more likely to get a girl and if you have baby-making sex right at ovulation, you're more likely to get a boy), it lines up somewhat with current hormonal theories.
This may explain some of the things that Dr. Shettles and other doctors saw in the past, even though they didn't understand exactly why it was happening or they had a false theory on why it happened. It means that timing intercourse to choose your baby's gender is still a valid thing to consider.
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