Do iron pills affect the birth control pill?

no
An iron supplement shouldn't interfere with your Birth Control.

I have been taking iron for the past 5 months (one 100mg tablet a day) and I am also using birth control. Both of these were prescribed to me by my doctor, so I doubt there is any negative interaction. Nor have I had any problems with my birth control in the past few months either, so yes I think it's safe.