Found this article CJ (beware the music!) - will go off and look for more
http://www.merrydancercats.btinterne..._pregnancy.htm
and this from the Purina site
How can I tell if my cat is pregnant?
If you do not get your cat spayed, they cat may become pregnant. You will not be able to tell if your cat is pregnant until the 2nd or 3rd week of the pregnancy. The pregnancy will last 63 days. Signs may include enlarged nipples (may change colour & harden to prepare for lactation) and a swollen belly from around 4-5 weeks.
We would recommend taking your cat to the vets for a check up to confirm pregnancy. Once there, the vet should be able to advise the best course of action.
and another
Weeks 3 and 4 - Days 15 - 28
At this point the queen should give you some indication that she is indeed carrying precious cargo. The first most noticeable sign is the pinking and enlarging of her nipples (usually referred to as ‘pinking up’), the fur on her belly will become thinner and move away from the nipples leaving a small bare circle (perfect for little mouths to suck without getting a mouthful of mum’s coat). Maiden queens may not pink up as visibly as expected (more experienced queens may light up like a beacon and get nipples like ‘coat-hangers’). Some queens also suffer from morning sickness and go off their food for a little while. Her coat will become glossy and she will look and feel on top of the world, purring to herself on many occasions - some queens get that 'glassy-eyed and content' look that many human mothers experience at five to six months (just before they become unbearably fat, awkward and miserable). At this point it may also be possible to feel the kittens as small ball-bearings placed along the uterus - be careful though as too much prodding and poking could cause damage
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