It's no secret that women suffer a great deal in the sleep deprivation area, especially through the child bearing years. How many times have you tried to catch up on your sleep after a night or two nursing a sick child?
Bad news. Science Daily tells us that you never catch up on lost sleep:

Now sleep researchers at Northwestern University have discovered that when animals are partially sleep deprived over consecutive days they no longer attempt to catch up on sleep, despite an accumulating sleep deficit. Their study is the first to show that repeated partial sleep loss negatively affects an animal's ability to compensate for lost sleep. The body responds differently to chronic sleep loss than it does to acute sleep loss.

Management Issues warns:

Chronic partial sleep loss of even two to three hours per night has a noticeable effect on the body, leading to impairments in cognitive performance, as well as cardiovascular, immune and endocrine functions.

Particularly worrying is the fact that sleep-restricted people often don't feel tired even though their performance on tasks has markedly declined.