hi there...

at three weeks pregnant, i think you shouldn't worry much. cat's gestation period is around 63 days from the mating day.

at this stage, give her kitten food, the best one you can afford.

when she's about to deliver, two three weeks time, prepare a place for her and the kittens. as for me, usually i prepare the cat carrier. put a new rug in there and few days later, replace with a new one. or you can use a cage so that the cat deliver in the cage.

usually cat deliver without difficulty, should you suspect anything amiss send to the vet. or just send to the vet if you think you cannot handle the delivery.

for your info, i have five a week old kittens in my house. i love to see them!

good luck friend!

p/s : do more research ya...