How do you know a cat is pregnant? Well, with a cat that is far along, it is obvious enough, but in the early stages the first real sign is that the nipples change from light pink to darker pink, which occurs around the third week after mating.
This isn’t as certain a sign as feeling the lower abdomen to see if any tiny fetuses are present. Radiography, which is harmless to the mother and the kittens, gives a very accurate picture of how many kittens are in a litter. At about fifty-five days after conception, a kitten’s entire skeleton is visible.