The first external sign of pregnancy you may see is a change in nipple color from pale to dark rose pink, and hair loss around the nipple area making them more prominent. These changes appear about three weeks after successful mating. Three or four weeks following conception it is often possible for a veterinarian to feel the fetuses in the uterus through the abdominal wall. At this time they are distinct round lumps in the uterus.
Later the fetuses are not so distinct, but usually a veterinarian can still confirm pregnancy by palpation. If necessary, an ultrasound examination can be used to detect kittens at two to three weeks or a blood test can confirm pregnancy as early as six days post breeding. An X-ray picture taken after five and one-half weeks of pregnancy (when the kittens’ bones are ossified) can also be used for confirmation of pregnancy and to determine the number of kittens present.
Following a sterile mating, which occasionally occurs in cats, false pregnancy (pseudopregnancy) may occur. Although signs are not usually marked, milk production may occur, and a rare cat may even make a nest and go through a pseudolabor. False pregnancy usually terminates spontaneously about five weeks after breeding. Hormones and/or prolactin- (lactation-stimulating hormone) inhibiting drugs can be administered by a veterinarian to relieve severe signs of pseudopregnancy.
It is best, however, to avoid hormone treatment if possible, since reproduction-modifying drugs have side effects in cats, and following hormone treatment some cats appear to remain in continual estrus or anestrus. Cats with repeated pseudopregnancies should have an ovariohysterectomy to prevent recurrent signs.