When Is It Safe To Have Unprotected Sex While On Birth Control Pills?

My girlfriend started taking her birth control a little over a month ago. At first, she was on her pill that was a too high of a dose and had to get off of it, and started a lower dose a week later. She is about to get done her first month of being on the pill regularly. She is due for her first period while on the pill in exactly a week. When is it safe to have unprotected sex since she started the pill? We are in a monogamous relationship and both of us are STD free.