Walk into a fertility clinic and ask for help conceiving, and one of the first questions the doc will ask is: Do you smoke? That goes for men and women. You don't need us to tell you that cigarettes contain hundreds of chemicals and that nicotine constricts blood vessels, which can impair the ability of the fertilized egg to implant. Smoking and exposure to second-hand smoke interfere with a couple's ability to conceive, as well as the ability to carry the baby to term. In the event that in vitro fertilization (IVF) works, smokers require twice as many treatments. And exposing a fetus to smoke in utero can harm your shot at having grandkids some day.
Source: "Smoking and infertility," Fertility and Sterility