This really grinds my gears (I've worked in pharmacy since I was 18, so going on 16 years omg). The most current research is that the only antibiotic that affects birth control to any measurable amount is rifampin or rifampicin-like antibiotics. Know what those are used for? In the US, tuberculosis and meningitis. Not sinus infections, not UTIs, not bronchitis. TB and meningitis. So a very preventable illness uncommon outside of immigrant populations in this country and an infection that they would've had to have been vaccinated for before living in a dorm at college. As of a few years ago, there were some who thought ampicillin could decrease efficacy but they haven't been able to substantiate that and ampicillin is rarely used anyway.Eurgh her comment about antibiotics cancelling out birth control. Very few antibiotics cancel out birth control now - read the damn pamphlet instead of spreading false information.
You should always, always, always ask your damn pharmacist and doctor about the most current peer-reviewed research and recommendations, and also if you don't want kids right now, use a back up method. This is common sense. If you're not preventing, you're trying.
k getting off my high horse now.