What can happen if you do drugs and you might be pregnant?
It can cause birth defects. I don't know whether you mean prescription or illegal drugs, but you should go see your doctor ASAP to find out. Even prescription drugs can harm an unborn child - and badly. Doctor. Go.
Well, different drugs cause different problems, but pretty much any drug, even caffeine, can harm your baby. Unless you plan on having an abortion, you need to stop doing drugs -- all drugs, even marijuana, cigarettes, and coffee -- right now. Especially alcohol. Just four drinks in one night, or one drink every day for less than a week, can cause Fetal Alcohol Syndrome (which is basically like a form of retardation, with other symptoms like vision problems, abnormality of facial features, growth problems, and more).