Is nicotine addiction dangerous for pregnant women?

Yes and for fetus. Smoking cigarettes has harmful side effects. However, doing so while pregnant has harmful side effects not only for the mother but also for the developing fetus. Exposure to nicotine even when not in smoked form is not recommended during pregnancy. Great time to quit!
Yes. Mothers that smoke usually have smaller babies due to the compromise in the blood circulation thru a placenta that is damaged by the nicotine. Also mother that smoke will undergo menopause two to three years sooner than those that don't smoke.