Lactation supplements

This is my 3rd baby. No issues with my first breastfeeding, I had an overwhelming supply. Not the case with my 2nd. There was definitely a struggle with being able to feed and stock extra supply also. I’ve been looking into a lot of lactation supplements. My question is, is this something I should begin prior to giving birth? Does that even help? Or not necessary until after? I’m aware I won’t know what my supply will be like, but I’m nervous I’ll be struggling again. Thanks for your input!