Who does this?

Why do people say elevate your legs after having sex for 20 mins for the sperm to get where it needs to? I mean i have children before and i honestly didn’t have to do this to end up being pregnant. I was told by my doctor that by the time your partner ejaculates and before he even pull out the sperm already up the cervix🤷🏽‍♀️🤷🏽‍♀️ Did you have to elevate legs to get pregnant or do u even keep your legs elevated after sex?