The dangers of smelling secondhand smoke during pregnancy are as follows: first, secondhand smoke contains more harmful substances, such as nicotine and tar, which may affect the growth and development of the fetus, and may also cause cancer and various diseases; second, secondhand smoke during pregnancy may lead to miscarriage or premature birth, and may also cause various fetal neural tube malformations, cleft lip and palate, etc. The problem will cause direct harm to the growth and development of the fetus. Therefore, you must pay attention to the best not to often smoke secondhand smoke, and at the same time during pregnancy to regularly go to the work of detoxification, in order to avoid various problems such as fetal malformations, pregnant women in pregnancy is best not to smoke, drink alcohol, so as not to affect the development of the fetus, to pay attention to the protection of the body, to avoid the invasion of harmful substances in the body.