Nuvaring and antibiotics

My girlfriend is currently using the nuvaring, she also happans to be using antibiotics. While having (unprotected) sex I finished before withdrawing, shes now scared and upset with me that I did that, Do I or we having any thing to worry about, what percentage is it that the antibiotics decrease the effectiveness of the ring

Thanks

Hey you and your girlfriend have nothing to worry about, antibiotics don't effect the Nuvaring like they do with "the pill"
This is an article from a medical journal that can confirm this for you.