Children often have acute, short-term illnesses such as upper respiratory tract or ear infections, gastrointestinal illness with vomiting and diarrhea, or injury-related problems. However, some children develop chronic illness (lasting for years or even lifelong) as a result of genetic (inherited) conditions, environmental factors, or a combination of both. Because prenatal (before birth) exposure to tobacco smoke and alcohol can affect a baby's health, it is important to extend environmental and nutritional concerns to women who may become pregnant. The February 17, 2010, issue of JAMA includes an article about changes in the prevalence of chronic conditions among US children from 1988 through 2006. This Patient Page is based on one previously published in the June 27, 2007, issue of JAMA.