According to the CDC, no amount of alcohol during pregnancy has been proven safe. However, it is unlikely that the occasional drink (defined as a mixed drink with one ounce of alcohol, a five-ounce glass of wine, or a twelve-ounce beer) taken before you learn you are pregnant will have harmed your developing embryo.
There is real danger to your baby, however, if you're drinking heavily (defined as more than seven drinks per week) or binge drinking (defined as more than five drinks on one occasion). If you're concerned about your drinking and are afraid you may have trouble giving it up during pregnancy, talk to your healthcare provider about counseling or treatment options.
I'm a smoker.
According to the March of Dimes, smoking during pregnancy nearly doubles your risk of having a low-birth-weight baby. In addition, it can increase your risk of miscarriage, preterm delivery, premature rupture of membranes, and problems with the placenta. Obviously, it's best if women quit before they even become pregnant—but what if you didn't?
"The sooner you quit, the better," says Dr. Greenfield. "Most of the complications with smoking have to do with smoking throughout the pregnancy." When you quit, your baby starts to reap the benefits of your decision almost immediately. And keep in mind that it's never too late to stop smoking.