Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations. There are over 19 known chemical carcinogens in cigarette smoke. Tobacco also contains nicotine, which is a highly addictive psychoactive chemical. When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, it contributes to a number of other threats to the health of the fetus such as premature births and low birth weight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS). The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb may reduce the fetal brain's ability to recognize hypoxic conditions, thus increasing the chance of accidental asphyxiation. Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers, and is a key factor causing erectile dysfunction (ED).