Second-hand smoke is worse than first-hand smoke. Studies have shown that babies of non-smoking moms who are regularly exposed to cigarette smoke are at increased risk for a number of health problems, including delayed growth, low birth weight, learning disabilities, behavioral issues, and possibly some childhood cancers. You should also make sure to steer clear or ask friends and family not to light up when you're around. Most people should be very understanding about not smoking in the presence of a pregnant woman.