Gestation is the period from conception to birth. From the first day of a successful mating, it averages 65 days. Kittens born from day 63 to day 69 fall within the normal range. Siamese cats may carry their kittens 71 days. However, if the kittens are born before day 60, they usually will be too immature to survive.
The uterus of a cat has two horns that are connected to the central uterine cavity. The cervix is the outlet to the vaginal birth canal. Developing kittens, encircled by their placentas, lie within the uterine horns.
At present, there is no early pregnancy detection test available for cats the way there is for people. During the first few weeks of gestation, few signs are detectable except for a slight gain in weight. Abdominal ultrasound done by an experienced evaluator may detect pregnancy as early as day 15. Fetal heartbeats, detectable at day 20, provide absolute indications of life.
The cat’s uterus is Y-shaped with a horn on each side. The kittens grow and develop in the uterine horns. Twenty days after conception, the growing embryos can be felt by abdominal palpation as evenly spaced swellings about the size of unshelled peanuts. Palpating the queen’s abdomen requires experience and gentleness, and should only be done by a veterinarian or an experienced breeder. There are also other structures in the abdomen that may feel lumpy. Excessive poking and prodding can damage the fetal-placental units and cause a miscarriage.
Cats occasionally suffer from morning sickness. This usually happens during the third to fourth week of pregnancy and is due to hormonal changes and the stretching and distention of the uterus. You may notice that your queen appears apathetic. She may be off her food and vomit from time to time. Morning sickness lasts only a few days. Unless you are particularly attentive, you may not even notice it. If your cat goes more than two days without eating or is not drinking, you should have her evaluated by your veterinarian.
The Witness Pregnancy Detection Kit, which was designed to detect the hormone relaxin in dogs, can also be used for cats to detect pregnancy after about 30 days.
By 35 days, the nipples become pink and obvious, and the size of belly is increasing. The fetuses are floating in capsules of fluid and can no longer be detected by palpation. As the time of birth approaches, the breasts enlarge and a milky fluid may be expressed from the nipples. However, many queens have breast enlargement after a normal heat, so this alone should not lead to a pregnancy diagnosis.
Ultrasounds are noted for being very accurate fairly early on in detecting pregnancy, but they are not as valuable as X-rays for determining the exact number of fetuses. Ultrasound can indicate viability, though, showing fetal heartbeats. An abdominal X-ray will show fetal bone structure past day 43.
X-rays are also used as an alternative to ultrasonography when it is necessary to distinguish among pregnancy, false pregnancy, and pyometra. They should be avoided in early pregnancy.
By day 49, the kittens are sausage-shaped and their heads are large enough to be felt as separate structures. Late signs of pregnancy are an obvious
pear-shaped abdomen and fetal movements, easily detectable during the last two weeks.