Are there any advantages of taking prenatal vit early?

So I know when you get seen by the obgyn when your pregnant to start taking prenatal vitamins but some start taking before they even get pregnant. I was just curious if there was any advantages of taking them before you get pregnant? Like, do you get pregnant easier? No negativity please such as, "DUH, this is such a stupid question!" There is already enough negativity on this app to last for weeks .