Do mums to be take folic acid only once they find out they're pregnant, or even before they get pregnant?

If you already know that you want to have a baby then you should be taking it before the pregnancy. I only started taking after I missed my period. Self denial mode for a month. Haha. I puked it all out every single time I took it anyway. So I'm not sure how much of it I really absorbed. This was what I took: