It's time to prepare a box which is warm and placed in a quiet, private place. Your cat may not use the box for her delivery, but she will readily accept you moving the litter to the box when she is done with her delivery. Remember pregnancy lasts approximately 63 days in a cat. Seventy two hours prior to the birth, the mammary glands will begin to swell. Twenty four hours prior to delivery, the cat will stop eating and milk will be available at the mammary glands.
Cats have very few problems with delivery.
We can unintentionally make that delivery more difficult by our desire to be helpful. Once the female begins labour, it is important that the family doesn't hover anxiously over the cat with bright lights and confusion awaiting the presence of each kitten. This will greatly inhibit the birth. I have frequently taken pets into my hospital who are having a difficult birth, and done nothing more than place them in a dark quiet room, undisturbed, where the labour proceeded without problems. It is Okay to check the mother every 30 minutes by quietly peeking in on her.