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Fewer than 10% of babies are born on their exact due dates, 50% are born within 1 week of the due date, and 90% are born within 2 weeks of the date.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.
Alzheimer's disease affects only about 10% of people older than 65 years of age. Most forms of decreased mental function and dementia are caused by disuse (letting the mind get lazy).
IgA antibodies protect body surfaces exposed to outside foreign substances. IgG antibodies are found in all body fluids. IgM antibodies are the first type of antibody made in response to an infection. IgE antibody levels are often high in people with allergies. IgD antibodies are found in tissues lining the abdomen and chest.