Most Americans are not financially prepared for the possibility of becoming disabled and unable to work, according to the National Association of Insurance Commissioners (NAIC). A 2007 survey by NAIC found that 56 percent of adults say they would be unable to pay their bills or meet expenses if they became disabled and could not work for a year or longer.

Only 13 percent of Americans think it's somewhat or very likely they would become disabled and unable to work, according to NAIC. However, a 20-year-old worker has a 3-in-10 chance of becoming disabled before reaching retirement age, according to the Social Security Administration.

Disability insurance replaces a portion of your income if you are unable to work because of injury or illness. Short–term disability (STD) insurance replaces a portion of your salary for typically three to six months following a disability. Long–term disability (LTD) insurance coverage usually begins after you are unable to work due for at least six months. Disability policies are generally purchased as group policies through work.

Maternity is a common claim covered under group STD plan. Even so, a 2002 MetLife survey found most women don’t realize disability plans cover maternity. According to the survey, 27 percent of women between the ages of 21 and 39 didn’t know maternity is covered, while 45 percent are not sure.

In addition about half of all short-term disability insurance claims are the result of the five most expensive diseases and illnesses in the United States in terms of medical expenditures, according to 2006 MetLife claims data. These five ailments — heart conditions, trauma, cancer, mental disorders and pulmonary conditions — account for an average of 60 percent of all lost workdays due to a short-term disability.