Smoking is more harmful to adolescents. According to medical research, adolescents are in the growth and development period, the physiological systems and organs are not mature, the resistance to external harmful factors is weaker than adults, easy to absorb toxic substances, damage the normal development of the body. According to a survey of 25 states in the United States, the age at which smoking begins is positively and negatively associated with the risk of death from lung cancer. If the risk of death from lung cancer for nonsmokers is positioned at 1.00, the risk of death from lung cancer for those who start smoking under the age of 15 is 19.68; for those who start smoking between the ages of 20 and 24 is 10.08, and for those who start smoking over the age of 25 is 4.08, indicating that the earlier the age of starting smoking, the higher the risk of lung cancer occurrence and death. Smoking damages the brain, causing slow thinking and memory loss, which affects learning and work, and reduces students’ academic performance. Studies have shown that the intellectual effectiveness of smokers is 10.6% less than that of nonsmokers. Smoking is harmful to pregnant women and fetuses First, smoking can reduce the fertility of both partners. In the United Kingdom, an 11-year study of 17,000 women of childbearing age showed that the infertility rate among women who smoked more than 10 cigarettes a day was 10.7 percent, compared with 5.4 percent among nonsmokers. Another survey also showed that women who smoked were 2.7 times more likely to suffer infertility compared to non-smokers; if both couples smoked, they were 5.3 times more likely to be infertile than non-smoking couples. Several studies have found that nicotine in tobacco has an effect on sperm shape, energetic force, linear swimming ability and the ability of sperm to penetrate the egg, and the higher the nicotine concentration, the greater the effect. A British study also confirmed that: sperm concentration and percentage of active sperm were significantly lower in the smoking group than in the nonsmokers, with an average of 25 million sperm/mL in the semen of the smoking group and 63 million sperm/mL in the nonsmoking group; active sperm accounted for only 49% of all sperm in the smoking group, but up to 63% in the nonsmokers, indicating that smoking is one of the important causes of male infertility. The fertilization rate of eggs in women who smoke is greatly reduced, and British researchers found that the breakdown product of nicotine, cotinine, had a significant effect on conception through observations of 45 infertile women who underwent in vitro fertilization. Cortisone affects the production of androgens during a woman’s reproductive cycle, and the percentage of fertilized eggs was reduced by 60% in women who smoked compared to non-smokers. Second, smoking in women is extremely harmful to fetal development and health. Tobacco contains a large number of toxic substances, in addition to the well-known nicotine, but also hydrocyanic acid, ammonia, carbon monoxide, carbon dioxide, pyridine, aromatic compounds and tar. These toxic substances can be absorbed into the mother’s blood with the smoke, causing the maternal blood oxygen level to decrease and the placenta’s blood oxygen level to decrease as well. The fetus can suffer from growth retardation due to lack of oxygen. Pregnant women who smoke give birth to low birth weight babies (weighing less than 2,500 grams) twice as often as non-smoking women, and these low birth weight babies are weaker, have an increased risk of serious illness and higher mortality within one year of birth. Recent studies have also shown that pregnant women who smoke are more likely to have miscarriages, premature births, and stillbirths than non-smoking pregnant women, and that smoking during pregnancy can even jeopardize the fertility of their children as adults. In addition, maternal smoking can increase the incidence of congenital malformations in the fetus. Some data show that the number of congenital malformations born to mothers who smoke is 2.3 times higher than that of non-smoking mothers, and the incidence of anencephaly, cleft palate, cleft lip, dementia and physical developmental disorders is 2.5 times higher than that of non-smokers. 30-40% of sudden infant deaths are related to the smoking habits of pregnant women, and the risk of sudden infant death is three times higher in women who smoke during pregnancy than in non-smoking women. Smoking during pregnancy is also very bad for pregnant women themselves. Reports show that pregnant women who smoke are 1-2 times more likely to have placental abruption, hemorrhage, premature water breakage, and other complications than normal pregnant women. For the sake of the healthy growth of the next generation and the health of the pregnant women themselves, pregnant women should stay away from cigarettes and avoid passive smoking, and spend their pregnancy and childbirth in a fresh and pleasant environment.