Cats are pregnant for approx 65 days, so it's not possible for them to have 7 litter per year! They can get pregnant again almost as soon as they have given birth, which would mean that mathematically it would be possible for them to have about 5 litters a year, although I would imagine there are other factors that would prevent a cat getting pregnant quite that often. My guess would be 3-4 times a year if left to their own devices.