Prolonged anestrus can be caused by malnutrition, genetic causes, hormonal imbalance, and disease. Cats that lack exposure to other cats or to at least 12 hours a day of light, may not have normal heat cycles. Precociousness (early sexual maturity) can occur in kittens as young as 4 months of age. Good nutrition, adequate light, and contact with older cats with normal heat cycles may result in early cycling-going in and out of heat regularly. It is not advisable to breed these very young females; small litter size, difficult labor and birth, and a greater incidence of birth defects are some of the many valid reasons to wait until the kitten is mature enough physically. Nymphomania may occur in older females that never had a litter. These cats usually have cystic endometrial hyperplasia-pyometra complex, which generally occurs in female cats aged 3 to 14 that have never borne kittens. Pseudopregnancy (false pregnancy) may occur following a strile mating, stimulation of the vulva of the cat, or spontaneous ovulation.
Because of the risk to the developing kittens, all medications, including vaccines, should be avoided during pregnancy. Griseofulvin, a drug commonly used to treat ringworm, can cause birth defects. Cats that are otherwise healthy but have recurrent miscarriages at the same point of gestation are thought to suffer from progesterone hormone deficiency. Injections of progesterone may be helpful.
Bacterial and viral infections can cause infertility in the queen. Feline panleukopenia, feline leukemia and feline infectious peritonitis have all been proven to do so.
Cystic hyperplasia, the first disorder of the complex to develop, involves a thickening of the uterus lining and cyst formation; victims usually display no signs except for infertility. Endometritis can develop during or after cystic hyperplasia. Cats with endometritis often have no signs of disease, although a vaginal discharge may be evident in some cases. Untreated endometritis may develop into pyometra. As the disease progresses, the cat will appear steadily more ill. In the final stages, there will be a bloody uterine discharge and depression; laboratory tests will show an elevated white blood cell count. Generalized infection leads to a rapid death.
The early stages of this disease complex may be treated successfully, but treatment becomes more difficult as the disease progresses. Unless the cat is essential for breeding purposes, an ovariohysterectomy (spay) is recommended.
Chronic infections of the cervix and vagina may cause infertility. A slight discharge may be evident, but is often overlooked due to the cat's normal cleaning habits. Those infections usually occur following injury or difficult delivery of large kittens. If not treated, they may cause scarring and even closure of the cervix.