Assuming that Medicare Part Acovered her first stay in the rehab facility, her second hospital and rehab facility stay will still be considered part of the same benefit period. That's because she won't have been out of the hospital and rehab center for 60 consecutive days (she'll only have four weeks -- 28 days -- between inpatient stays), which Medicare rules establish as the requirement for a new benefit period. There will be both financial plusses and minuses for her because of this situation.
For each new benefit period, your mother must pay a hospital deductible of $1,024 (in 2008). Because both hospital stays will be considered part of the same benefit period, she will not have to pay another deductible for her second hospital stay. After the deductible, Medicare Part A pays 100 percent of covered care for the first 60 days in the hospital. So, if your mother is in the hospital for a total of less than 60 days in both stays combined, she won't have anything to pay for hospital care (except for the one deductible).
Her payments for stays in the rehab facility are a different story. In any one benefit period, Medicare Part A covers up to 100 days in a nursing or rehabilitation facility. For the first 20 days in any one benefit period, Medicare Part A pays the full amount. But for the next 80 days in a benefit period, the patient is responsible for a daily copayment of $128 (in 2008). Because she already went beyond 20 days in her first rehab facility stay, your mother will be responsible for $128 per day for every day she spends in the rehab facility during her second stay -- because it will still be part of the same benefit period.