The main reason why you should quit smoking and drinking is to ensure that you have a good pregnancy. It is generally recommended that both men and women quit smoking during the preparatory period. Long-term smoking and drinking, the nicotine and tar in the cigarettes and the alcohol in the wine will not only jeopardize health, but also lead to a decline in the quality of men’s sperm, so that sperm vitality is weakened, the number of sperm decreases, or dead sperm and so on. And it will also affect the quality of women’s eggs, thus increasing the difficulty of conception, even if the pregnancy is prone to miscarriage or fetal deformity, stillbirth and other accidents. In order to ensure eugenics, it is recommended to quit smoking and drinking 3 months before pregnancy, women should take folic acid supplement, men should exercise properly to enhance their physical fitness, avoid exposure to radiation tests and harmful substances, etc., and choose the best physical and mental state of the couple to prepare for pregnancy.