If you're not sure of the date your cat conceived, you may not know how many weeks pregnant she is. Knowing her due date is helpful, as you can prepare for the birth, find homes for the kittens and watch for signs of labor. Fortunately, there are a few ways in which to know how far along your kitty is.
Observe the color of your cat's nipples. The nipples of most pregnant cats will become pink after about three weeks of pregnancy.
Look at your cat's stomach. If your cat is pregnant, you will likely notice an increase in the size of her abdomen; however, this typically doesn't appear until she is about four to five weeks pregnant---about halfway through the pregnancy.
Monitor the size of the nipples. At about 6 weeks along, the cat's nipples will grow and fill with milk.
Take your cat to a veterinarian. The doctor can take a radiograph of the cat's belly and determine the age of the kittens based upon the size of their skeletons, their bone density and formation. Upon palpation, the doctor can also feel golf ball-sized lumps inside the cat when she is about four or five weeks along.
Note any movement in kitty's belly. About two weeks before your cat goes into labor, you can feel the kittens moving inside her stomach. It's actually possible to see the kittens move a little further into the pregnancy.
Watch for any signs of restless or nervous behavior. Cats are pregnant for about 57 to 70 days. A few days before labor takes place, a feline will typically search for shelter and rearrange her bedding material.