Your vet can do an ultrasound....
The best thing to do is take the cat to the vet, or get the vet to visit. Alternatively, if you have a breeding mentor, they may also be able to tell. Calling a vet, however, is particularly important if the unborn kittens are no longer alive, as these will need to be removed immediately as they can cause infection in the mother cat's womb.
Take your cat and kittens to the Vet.
You need to go to the vet and, see how many kittens there are. If you need them removed do the same go to the vet and they can do ex-rays to find out!!
Are you sure she was spayed? A fixed cat cannot have kittens as the procedure removes all the reproductive organs; the uterus and the ovaries. There is a chance that the vet did not do the procedure correctly or at all, but there really is no way to tell; the only person who can really answer this question is your vet, or the vet that spayed your cat. Vets will not spay a cat that is already well in her pregnancy, as the risk is far too great for the Queen. A vet will only spay a cat very early on as the risk of the Queen bleeding out or some other complication is minimal.
your cat may have a disease. or is just unable to carry kittens. either that or the father might have a disease. a disease that makes them unable to have kittens. you should take your cat to the vet to see why.
you can tell by seeing if it produces milk while the animal is in heat. take it to a vet for a check up before breeding. or wait and see if anything happens.
Check with your vet before giving your cat any medications, especially if it is nursing. Medications can pass through the cats milk and harm the kittens.
You should take your cat to the vet!
No, it is not possible for a spayed cat to have kittens. The spaying procedure removes the cat's entire reproductive system, which includes any unborn kittens if any are present. If the cat is far into her pregnancy, it may be safer (unless a vet says otherwise) to let the kittens be born and then spay the mother as soon as the kittens are weaned. A cat early in pregnancy can be spayed safely.
Gather up your cat and the kittens and take her to the vet. Seconded. If you don't she will probably/certainly die, and then the kittens will, as the will have no mother to feed them.
It depends on what stage in her pregnancy is she being spayed? If your Veterinarian is spaying her in the beginning stages of her pregnancy, the kittens will not live. If he is doing this in the late stages of pregnancy, which I don't think most Vets would do unless it is an emergency situation for the Mother cat, then the kittens might live. It is best if you have to spay your cat while she is pregnant, to do it in the early stages and that is probably what your Vet is doing as it is much easier on the Momma cat.
take it to a vet