A lot of cultures have a lot of weird superstitions and myths related to childbirth.
I had a Nepalese friend who once told me that if you conceive on a weekend you would have a girl but if you conceive on a weekday you would have a boy.
I pointed out that it must just be a coincidence then that our species has nearly an equal number of men and women, and he agreed that it was a great coincidence.
I then asked him how often that superstition was correct and how often it got it working, he said about 50/50.