Men who are planning to become fathers have another good reason to quit smoking. Smoking can reduce sperm count, as well as cause serious abnormalities in the shape and movement of sperm, so it may contribute to infertility. Even if you have conceived successfully, a smoking habit can still harm your unborn child. Nonsmoking women whose partners smoke are at increased risk of having a low birth weight baby (less than 5 1/2 pounds) due to the effects of secondhand smoke. Low birth weight babies are at increased risk of health problems during the newborn period and of lasting disabilities; they are also about 20 times more likely to die in their first year of life than normal-weight babies. And once a baby is born, studies suggest that living with a smoker increases his risk of sudden infant death syndrome (SIDS), as well as lower respiratory infections and asthma.
While pregnant women who drink risk having a baby with fetal alcohol syndrome (characterized by mental and physical birth defects), there's no evidence that a father's drinking can cause this problem. However, heavy drinking may reduce a man's sperm count and fertility. It may also affect his relationship with his pregnant partner. As with cigarettes or drugs, if an expectant father brings alcohol into the home, it may make it harder for his partner to avoid these types of habits.