I think my cat may be pregnant, but I'm not sure. She is getting fatter, and she did run away for a while. Are there any signs I could look for to tell if she is pregnant?

Take it to the vet

Most cats are very fertile. If your pet has had access to the outside world while she was in heat, she is probably pregnant. Pregnancy in the cat can be detected in several ways. First, your veterinarian can palpate the cat's abdomen at about 23 days of gestation and detect the fetuses in the uterus. Another method would be to perform an ultrasound examination. This can be performed to evaluate the status of the uterus at any time. At about 40 days of gestation the fetal skeletons ossify, or harden into bone, and an x-ray can detect the kittens. X-rays in late pregnancy are a safe way to both detect pregnancy and to find out how many new mouths there will be to feed. It takes 61 to 63 days for kittens to gestate. Prior to your cat giving birth you may notice mammary development and nesting behavior. You will want to discuss with your veterinarian what needs to be done for your pet to ensure that her health and the kittens' health are good. If she is not pregnant now, you may want to get her spayed so that you will not encounter this problem again. Please check out the vetcentric.com encyclopedia article, "Spaying, Feline" for further information. When you take your pet to the veterinarian, the doctor will perform a complete physical examination. This is very important because if she is not pregnant, you will want to make sure that nothing is wrong that has made her appear to be heavy.