It's actually been shown to be safe during pregnancy. I saw a study where they followed the mothers while pregnant and then followed the kids once they were born all the way up to 12 years old and found no problems in the kids of even heavy smokers compared to the kids of non-smokers. The heavy smokers group was smoking over a half ounce a day, too! That's a lot! Considering how horrible morning sickness is and all the bad side effects of the medicines they prescribe to deal with it, I would totally choose marijuana over pharmaceuticals while pregnant.