Cats can become pregnant at an age as early as 4 months. Similar to humans, cats display periods of peak fertility, when they can get pregnant. This is commonly known as being in heat. This occurs about once every three weeks. During this time, the cat's behavior is noticeably different.
The gestation period for cats varies between 61 and 72 days, but the typical pregnancy lasts 63-67 days. Keep in mind that the signs of pregnancy do not occur as soon as it starts.
In the very beginning, the cat will not display specific signs of pregnancy. The early signs a cat is pregnant can be seen starting the second or even third week of pregnancy.