Is it ok to take OTC prenatal vitamins if I'm not pregnant?

I am hoping to become pregnant and am currently taking a multi-vitamin and an extra folic acid supplement. I’m 46 yr old & my husband is 47 & the only time I’ve been pregnant resulted in a miscarriage (at only about 2–3 weeks gestation) several years ago. I’m thinking it might be helpful due to my age for me to already be on a prenatal vitamin even before conception, but am wondering if there is anything that might be unhealthy (like too much iron) in a prenatal vitamin to take for months without being pregnant? Thanks very much.