If second-hand smoke is inhaled for a long period of time during pregnancy, it will have a serious impact on the growth and development of the fetus, and may even lead to the risk of miscarriage, fetal malformation, and cessation of fetal development. If a pregnant woman breathes in second-hand smoke during pregnancy, harmful substances such as nicotine and carbon monoxide in the smoke will directly stimulate the pregnant woman’s body, such as damaging the lining of the respiratory tract, increasing the risk of asthma, lung cancer and coronary heart disease, and if a pregnant woman’s cardiorespiratory function is affected, it will definitely affect the growth and development and quality of the fetus. If second-hand smoke is inhaled in the early stage of pregnancy, it may lead to miscarriage, make the fetus deformed, stop the development of the fetus, etc. If second-hand smoke is inhaled in the late stage of pregnancy, it may lead to the growth and development of the fetus is restricted. Therefore, pregnant women should avoid exposure to second-hand smoke, try not to enter environments with smoke, and take care to isolate themselves from pregnant women after their family members have smoked, in order to prevent the effects on pregnant women and the fetus.