Tobacco contains many harmful substances, some of which can enter the fetus through the placenta. Therefore, smoking during pregnancy is strictly prohibited. During pregnancy, all organs of the fetus gradually develop and mature as the pregnancy progresses. The fetal liver tends to mature in the late stages of pregnancy, but before the full term of pregnancy, the fetal liver is not well developed and has a poor detoxification capacity. Therefore, when smoking during pregnancy, toxins enter the fetus and cannot be broken down and metabolized. The accumulation of toxins can lead to fetal growth retardation and, in severe cases, fetal malformation and miscarriage. In addition, the toxins in tobacco can affect the development of the fetal nervous system. Studies have shown that the toxins in tobacco can cause a decrease in fetal intelligence. The above mentioned effects are caused by long-term smoking, but if the pregnant woman smokes less often during pregnancy, the effects are not very serious. It is important to emphasize that it is also not possible to smoke during pregnancy if the people around the pregnant woman smoke, and the pregnant woman will still experience the above-mentioned risks after inhaling the smoke. Therefore, smoking during pregnancy can have certain effects on the fetus and pregnant women are advised to stay away from tobacco.