Cats can get pregnant as soon as 48 hours after delivering. A cat typically goes right back into the heat cycle after giving birth, making her physically capable of becoming pregnant again. The heat cycle in a female cat occurs seasonally in the spring and fall, and she may go into heat several times during the season. It is possible for her to become pregnant during this time if she is accessible to a male cat, even if she recently gave birth or is nursing.
Although she is capable of getting pregnant again soon after delivery, other factors should be considered for the well-being of the animal. Cat pregnancy requires optimal health and it is beneficial to give her time between pregnancies to restore her energy. Waiting 4 to 6 months between pregnancies is safest. Becoming pregnant again while still nursing a litter of kittens will strain her health, and her body may not be capable of providing the necessary nutrients for her, her nursing babies and her unborn litter. She should be examined by a veterinarian before choosing to breed again to help ensure a successful, safe pregnancy for her and her kittens.
Preventing another pregnancy after giving birth requires keeping her indoors while she is in heat to separate her from any outdoor male cats that have not been neutered. She must also be kept apart from any male cat housemates that are not neutered, even if the male is the father of her current litter. A male cat will mate with her if she is in heat, despite the fact that she has just given birth, so separation is a must. Spaying is also an option to prevent future pregnancies. Spaying in a female cat is a surgical procedure in which the ovaries and uterus are removed. Spaying, while common and typically safe, is permanent--she will no longer go through any more heat cycles and no longer be able to reproduce. Wait at least 8 to 12 weeks after the delivery to get her spayed, or 10 days after the kittens have stopped nursing. She will need to continue producing milk for the kittens until they are fully weaned and have switched to solid foods.