1. Why should pregnant women quit smoking? Smoking can cause great harm to pregnant women and fetuses, including but not limited to the following aspects: 1. Increase the risk of premature birth: Smoking can cause slow intrauterine growth of the fetus and lower birth weight, thereby increasing the risk of premature birth. 2. Affect the intellectual development of the fetus: Smoking during pregnancy will affect the development of the fetal brain, making it less intelligent.