I'm planning to stop my ocp this saturday. How soon can I start takin prenatal vitamins. My husband and I are wanting to have a baby.?

Start now. There is no reason to wait. You can start taking your prenatal vitamins the day you decide it's time to start trying. Get the good ones, ie the vitamins that have 1 mg of folate (folic acid) per tablet. Some brands cause nausea, try a few brands if you need to. Good luck!