Smoking can gradually and permanently damage blood vessels throughout the body, including those that carry blood to the penis. This can make it difficult to get or maintain an erection (impotence). Quitting smoking may help prevent new damage from occurring inside the blood vessels.
Smoking can also affect a man's ability to get or maintain an erection in other ways that are not well understood. Nicotine may make the blood vessels narrower for a short time, which makes it more difficult to get enough blood into the penis for a normal erection. Men who quit smoking often have fewer problems achieving a normal erection.
During sexual arousal, a woman's genitals swell with blood. Nicotine narrows blood vessels, which makes it harder for blood to fill the genitals. So women who smoke may have less sexual sensation or feel less aroused.
Smoking while on hormonal birth control increases a woman's health risks, such as for blood clots, heart attack, and stroke. And birth control may not work as well, because smoking can lower the level of estrogen in the body.
Compared to women who do not smoke, women who smoke are likely to have longer and more painful and irregular menstrual cycles or periods.
Women who smoke take longer to become pregnant. But women who quit smoking before they try to become pregnant are as likely to become pregnant as women who have never smoked.