A laissez-faire attitude is the best option when caring for a mother cat who has just given birth to a litter of kittens. That means you should avoid interfering and let momma cat do what she does best, mother her babies. That's not to say there aren't things you can do to ensure mom is safe and healthy and the kittens get off to a good start in life.
Mother Knows Best
Most cats instinctively know how to care for their kittens, with little or no outside help. However, there are exceptions, especially when it's a cat's first litter. The best support you can give is to provide a quiet, calm environment. Monitor the mother and babies from a distance and be prepared to offer assistance or call a veterinarian when necessary.
Proper care for a mother cat begins long before she gives birth. To properly nurse her kittens, momma cat needs to be in good physical condition. She'll need a nutrient- and calorie-dense food such as good-quality commercial kitten kibble. Start feeding her this diet a few weeks before she is due to give birth, and increase the amount as she nears her due date. Because she needs to maintain a high-caloric diet during nursing, keep feeding it after the kittens are born.
Prepare a nesting box in a warm, low-traffic area of the house where you can watch it without disturbing your cat. Line it with towels and place your cat's food and water bowls close by. Also provide easy access to the litter box. Let her get used to the box, and hopefully she'll feel comfortable enough to give birth there. Chances are good she'll find her own place to have her kittens, but usually, if you place her and her kittens in the box, she'll make it her home.
Your cat typically will have little trouble delivering her babies. However, if she seems to be straining without producing a kitten, or if she doesn't seem to be caring for the kittens when they're born, you should call your vet. Monitor the birthing process to make sure momma cat licks the kittens as they are born, not just to clean them, but to stimulate breathing as well as elimination. It's also important that the kittens are nursing and being kept warm by the mother as they can't regulate their own body temperature for the first few weeks.
For the first 24 hours after delivery, the mother may not feel like eating. This is normal, but if it goes longer than that or she shows signs of illness such as panting or elevated temperature, call your vet. It's also normal for your cat to have a vaginal discharge for the first couple of weeks, but if it turns darker or has a foul odor, that's also cause for concern. Also check her nipples daily for redness or swelling, which could be signs of mastitis.
For the first two to three weeks, disturb momma and babies as little as possible. After about four weeks, start decreasing her food as she will be starting to wean her kittens and doesn't need as many calories. Also, keep the mother indoors and away from male cats as she can come into heat soon after giving birth, and becoming pregnant so quickly is hard on her body.