I don't think if affects the effectiveness, however it can lead to some serious health problems, and doctors are cautious when giving pills to patients.

Please if you take bcp's don't smoke. This can lead to very serious problems. My cousin died at the age of 32. The autopsy showed that she had developed a blood clot in her lung which broke free and went to her brain. The conclusion was that this was very possibly caused from smoking and taking birth control.

Don't know much about the side effects if you smoke while on bc. But everytime I went to the doctor for bc they tell me that I don't need to smoke while I was bc. Plus I don't smoke anyways.

The side effects are possible blood clots. That is why it is so dangerous to smoke and be on the pill.