Can you smoke weed while you're on birth control?

I went to the GYN yesterday and she made me pee in a cup. Which I'm not really worried about them seeing that I have been smoking because I'm pretty sure they only check to see if I'm pregnant. But anyways I know smoking cigarettes can cause like blood clots and stuff like that, but what about marijuana? I've never heard of any risks. And I sure don't want to counter act the birth control with weed because I don't want a baby!