Prenatal vitamins

My doctor prescribed me 5mg folic acid at the beginning of December when I told him we wanted to TTC. I didn't think much of it until the pharmacist asked why he prescribed it for me, to which I didn't have an answer, just thought that was a standard dosage, but either way I've been taking them daily.
​My friend suggested today that I also take a prenatal vitamin daily, so I bought materna by centrum, but noticed it also contains 1 mg of folic acid, and not sure I should take both. Of course I'll contact my doctor to inquire, but just wanted some input from others.