Men who smoke can have a negative impact on the fetus. The smoke from burning tobacco contains nicotine, tar and carbon monoxide, which can cross the placental barrier and affect the normal development of the fetus. Carbon monoxide affects the fetus’ access to oxygen, and men who smoke around pregnant women for long periods of time can cause oxygen deprivation in the fetus, affecting its physical development, especially its mental development. Men who smoke around pregnant women for a long time, pregnant women are exposed to second-hand smoke, the fetus has the risk of malnutrition, the probability of fetal death in the womb is also very high. Frequent passive smoking by pregnant women can lead to malformations in the fetal face or oral development and many dental problems as a result. Smoking by men can lead to excessive intake of toxins by pregnant women, which may lead to congenital malformations in the fetus, with loss of limbs, fingers, organs and other parts of the body, and the fetus will have a big difference in weight after birth compared to other newborns, which will be lighter. Large amounts of nicotine can cause great harm to human breathing, especially for the development of the fetal respiratory system, and some fetuses can be born with bronchitis, pneumonia, asthma and other respiratory diseases.