system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any factors that have actually been shown to affect which sex a baby will be when born?

I've heard of anecdotal reasons like mother's diet but have there been any serious studies on this topic?
gpt
There is one common proposition that sex during ovulation is *very* slightly more likely to result in a boy, while sex a few (2.5-3) days before ovulation, is *very* slightly more likely to result in a girl. This is because x sperm live longer than y sperm, but swim slower. Sex during ovulation means the faster y sperm will have a greater presence at the egg during fertilization. Sex before ovulation means that some of the y sperm will have died off, leaving a higher presence of x sperm. This is called "Shettles Method." However, remember that the odds are still very close to 50/50, and methods like this have a significant lack of non-anecdotal evidence. There is no known morphological difference between x and y sperm, according to the British Medical Journal.