During the first 2 weeks of pregnancy you will not be able to tell that your cat is pregnant. She may gain a slight amount of weight, but that won’t conclusively tell you that she’s pregnant.
At around 20 days your veterinarian can do an abdominal ultrasound, which will allow the vet to hear the fetal heartbeats. Around this time the kitten embryos can also be felt in your cat’s abdomen, but this must be done by a trained veterinarian. You must not try to feel the embryos yourself. Pushing on the embryos or abdominal area can cause your cat to miscarry her kittens. You should never do this intentionally.
Cats do get morning sickness! Cats experience morning sickness for a few days only, usually around the 3rd to 4th week of pregnancy. Morning sickness in cats involves vomiting, aversion to food, and lethargic behavior. Morning sickness in cats is caused by hormonal changes in her body.
At 5 weeks your cat’s nipples will become pink and protrude more than usual. The size of your cat’s belly will be increasing gradually and you may be able to notice a difference. Your cat’s breasts may enlarge and produce a milk-like liquid (although the breasts may enlarge during heat cycles as well, so you should not conclude your cat is pregnant based on breast enlargement only.)
At about 6 weeks the veterinarian will be able to view the fetal skeletons by taking an x-ray. X-rays should only be taken when it is really necessary and you should discuss any x-rays with your vet beforehand.
From week 7 until birth your cat’s belly will continue to grow and be noticeably larger. You will be able to see and feel fetal movement also!