You don’t need us to tell you that drinking and smoking during pregnancy are big no-no’s. Both can cause serious harm to your baby -- ranging from heart problems to mental defects. But it’s not a bad idea to cut back while you’re trying to conceive, in case you do become pregnant without realizing it. “You want your baby to have the best start possible,” says Dr. Hoskins. “It will also be easier to quit once you do find out you’re pregnant.” Encourage your partner to scale back, too: Excessive drinking and smoking can lower sperm count.