Does the antibiotic Macrobid decrease the effectiveness of birthcontrol?

[adycurious]

Does the antibiotic macrobid used to treat uti's decrease the effectiveness of birth control?  Because I'm on the pill and I shouldn't get my period for another week and I've been bleeding..  This makes me nervous because while taking macrobid I had sex without a condom, he pulled out, but I know that's not always a safe alternative either.
I know that during early pregnancy bleeding isn't uncommon. I'm scared out of my mind.. I'm completely against abortion and this anxiety is killing me.  Could it be something else that's causing me to bleed a week early while on the pill??

[John H. Kim, M.D.]

There is a small theoretical chance that the antibiotic can reduce the effectiveness of the birth control pill, so you should always use a back up.
Your early bleeding early probably means you are not pregnant but that the pill was not working as well.
Of course, you should check with your doctor if you continue bleeding and also check a pregnancy test.

[adycurious]

Yeah I did that, everything's alright.  Thank you for your help!