According to one source of 2004 data, approximately 13% of pregnant women reported smoking during the last 3 months of pregnancy. This is a major public health concern because smoking during pregnancy can lead to pregnancy complications and serious health problems in newborns, including a 50% increase in risk of low birth weight. The effect of tobacco exposure on infant birth weight may have long-term consequences, as fetal growth appears to be a predictor of coronary heart disease later in life. Pregnant women participating in clinical trials are less likely to disclose that they are smoking because of a desire to please study researchers. Therefore, a way to test for nicotine exposure is needed to accurately determine the number of pregnant women who smoke and the number of women who quit smoking during pregnancy.