SIDS victims sometimes show physical problems from the beginning, such as higher rates of prematurity and low birth weight, poor apgar scores, and limp muscle tone. Evidence shows that impaired brain functioning is one of the main contributing factors to SIDS. Between two and four months are when SIDS are most likely to occur, this is when reflexes start to decline and are replaced by voluntary, learned responses. Neurological weaknesses may prevent SIDS babies from acquiring behaviors that replace defensive reflexes (Lipsitt, 2003).  As a result, when breathing difficulties occur during sleep, these infants do not wake up, shift their position, or cry out for help, they simply give into oxygen deprivation and death. Several environmental factors are linked to SIDS. Maternal cigarette smoking, both during and after pregnancy, as well as smoking by other caregivers, double risk of the disorder. Prenatal abuse of drugs that depress central nervous system functioning, increase the risk of SIDS. SIDS babies are also more likely to sleep on their stomachs than on their backs and often are wrapped very warmly in clothing and blankets. Infants who sleep on their stomachs less often wake when their breathing is disturbed (Richardson, Walker, & Horne, 2008.) Others, healthy babies sleeping face down in soft bedding may die from breathing their own exhaled breath continually. SIDS rates are high among poverty-stricken minorities (Colson et al.2009) Parental stress, substance abuse, reduced access to health care, and lack of knowledge about safe sleep practices are widespread. The U.S. government’s Safe to Sleep campaign encourages parents to create safe sleep environments and engage in other protective practices. When SIDS does occur, surviving family members require a great deal of help to overcome a sudden and unexpected death.