Infertility in Female Cats
What is infertility?
Infertility in a queen (an unspayed or intact female cat) is defined as the inability to give birth to live kittens, despite appropriate breeding with a fertile male.
What is the normal estrous cycle in a cat?
Normal queens begin to have estrous (reproductive) cycles (heat cycles) at 4-12 months of age with the average onset at 6 months of age. The first estrous cycle may occur later in longhaired or larger breeds; these cats may start their first estrous cycle as late as 18 months of age. Estrous cycles in cats are influenced by daylight, typically requiring 14 or more hours of natural or artificial daylight to occur. For this reason, cats in the Northern Hemisphere typically cycle from January through October and may fail to cycle in the fall/winter months.
"Estrous cycles in cats are influenced by daylight, typically requiring 14 or more hours of natural or artificial daylight to occur."
The normal estrous cycle of a cat consists of several stages; the stage called estrus refers to when the female is sexually receptive or is in heat. The estrous cycle can range from anywhere between 1-6 weeks, with the average being about 3 weeks. Cats are induced ovulators, meaning that they will not ovulate unless mating occurs. If the cat mates during estrus, a surge of luteinizing hormone will trigger the release of the eggs from the ovary. Once this occurs, estrus will typically cease within one to two days.
What causes infertility in female cats?
There are numerous causes of infertility in cats. These may include a failure to cycle, a failure to successfully mate, a failure to successfully conceive, or a failure to carry a pregnancy to term.
Cats may have abnormal reproductive cycles, or fail to cycle. This can occur for a number of reasons. A queen that never enters her first heat cycle may be diagnosed with hereditary or genetic factors such as chromosomal abnormalities, hermaphroditism, or have abnormal uterine or ovarian development. A queen that cycles abnormally may be doing so due to environmental stresses, medications, or inadequate day length. Additionally, ovarian cysts and tumors may interfere with the cat’s reproductive cycle, through the release of various hormones.
A failure to successfully mate is often attributed to abnormalities or traumatic injuries to the reproductive tract. Both of these factors can physically prevent intercourse, or make it so painful that the female is unwilling to engage in copulation.
If a cat is bred too few times during estrus, or breeding is not completed, she may fail to ovulate. This may also occur if breeding is performed too early or late in estrus.
A number of uterine conditions can interfere with successful pregnancy (implantation of the fertilized eggs into the uterus). These conditions include pyometra (a bacterial infection of the uterus), cystic endometrial hyperplasia (an age-related change in the uterine lining), and inflammation of the uterus due to other causes. Infections may also play a role in preventing implantation, or in fetal abortion. These infections can include feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), calicivirus, panleukopenia, herpesvirus, or bacterial infections. Abortion may also occur due to noninfectious causes, such as nutritional inadequacy, environmental stress, and fetal chromosomal abnormalities.
What tests will my veterinarian perform to assess my cat’s infertility?
When attempting to determine the cause of your cat’s infertility, your veterinarian will likely begin with a thorough physical examination. This allows your veterinarian to assess your cat for systemic (whole-body) diseases that may be affecting your cat's fertility. Further testing will likely be based upon physical exam findings, and may include some or all of the following:
1. Laboratory testing. Screening bloodwork, including thyroid levels, can be used to assess your cat's overall internal health and look for possible causes of infertility. A urinalysis may also be performed, to assess for the presence of urinary tract disease (as the urinary and reproductive tracts are related).
2. Infectious disease testing. FeLV and FIV are common causes of feline infertility; therefore, your veterinarian will test your cat for these conditions. Other infectious disease testing may also be performed, depending on your cat’s clinical signs and history.
3. Vaginal cytology. In this test, your veterinarian will take a swab from your cat’s vagina and examine it under a microscope. Characteristic types of cells seen on cytology will allow your veterinarian to determine what stage of the estrous cycle your queen is in.
4. Vaginal culture. A sample of vaginal material may be submitted for bacterial culture, to assess for the presence of infection.
5. Hormone assays. Analyzing blood levels of progesterone and estradiol can allow your veterinarian to better characterize the stage of your queen’s estrous cycle.
6. Imaging. Ultrasound may be used to assess your cat’s uterus and ovaries.
How will my veterinarian treat my cat’s infertility?
Treatment of infertility, and its prognosis, depends upon its underlying cause.
"Treatment of infertility, and its prognosis, depends upon its underlying cause."
In all cases, cats are likely to benefit from improved management. Ensure that your cat is receiving adequate quantities of a high-quality, well-balanced diet. Keep your cat in a stress-free environment; take care to eliminate overcrowding and other sources of stress. All breeding females should receive at least 14 hours of daylight per day, and should be allowed to breed several times per day during estrus.
Your veterinarian may recommend injections to aid in inducing ovulation in young, healthy cats. Artificial insemination may also be considered in cats who refuse to mate.
Ovarian cysts or tumors may require surgical treatment, while cystic endometrial hyperplasia may be improved by medical treatment. Work with your veterinarian to determine the best course of action for your cat.
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