Smoking tobacco dramatically increases the risk of developing many diseases. It is responsible for a substantial majority of lung cancer and chronic obstructive pulmonary diseases, and most smokers die either from these respiratory diseases or from ischemic heart disease. Smoking also causes cancer of the upper respiratory and gastrointestinal tracts, pancreas, urinary bladder and kidney, and increases risk of peripheral vascular disease, stroke and peptic ulceration. Maternal smoking is an important cause of fetal growth retardation. Moreover, there is increasing evidence that passive (or "secondhand") smoking has adverse effects on cardiovascular and respiratory health.