Prenatal Vitamins

Kr
Question about taking prenatals...
I've read that taking prenatals if you're not ttc can actually be harmful. I'm currently ttc (going on 5 months now) and I'm down to my last few pills. I was curious if anyone had any information about continuing to take them for extended periods of time while ttc. It kind of doesn't make sense to me why it wouldn't be safe to take them while not ttc but it is while trying, even if that takes a while.