Infertility in Female Cats
What is infertility?
Infertility in a queen (an 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 cycles (also called heat cycles) at 4-12 months of age with the average onset at six months of age. The first estrous cycle may occur as late as 18 months of age in longhaired or larger breeds. 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.
"In cats, ovulation must be induced, meaning that they will not ovulate unless mating occurs."
The normal estrous cycle of a cat consists of several stages; the estrus stage refers to when the female is sexually receptive or is in heat. In cats, ovulation must be induced, meaning that they will not ovulate unless mating occurs. If the cat mates during estrus, a surge of the 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?
The causes of infertility in cats 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. A queen that never enters her first heat cycle may be diagnosed with hereditary or genetic factors such as chromosomal abnormalities, hermaphroditism (male and female sexual organs), or have abnormal uterine or ovarian development. A queen may have abnormal cycles due to environmental stressors, medications, or inadequate daylight. Additionally, ovarian cysts and tumors may interfere with the cat’s reproductive cycle through the release of various hormones.
"A queen may have abnormal cycles due to environmental stressors..."
A failure to successfully mate is often attributed to abnormalities or traumatic injuries to the reproductive tract. Both factors can physically prevent intercourse or make it so painful that the female is unwilling to engage in intercourse.
If a queen is coupled too few times or too early or too late during estrous, or if intercourse is not completed, she may fail to ovulate.
Uterine conditions can interfere with successful pregnancy. 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 include feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), calicivirus, panleukopenia, herpesvirus, or bacterial infections.
Abortion may also occur due to non-infectious causes, such as poor nutrition, environmental stress, and fetal chromosomal abnormalities.
How will my veterinarian determine the cause of 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. Further testing will be based upon physical exam findings and may include some or all of the following:
1. Laboratory testing. Screening blood work, including thyroid levels, can be used to assess your cat's overall internal health and point to possible causes of infertility. A urinalysis may also be performed to assess for urinary tract disease, as the urinary and reproductive tracts are related.
2. Infectious disease testing. FeLV and FIV are common causes of feline infertility, so your veterinarian will likely test your cat for these conditions. Other infectious disease testing may be performed, depending on your cat’s clinical signs and history.
"FeLV and FIV are common causes of feline infertility, so your veterinarian will likely test your cat for these conditions."
3. Vaginal cytology. 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 reveal which stage of the estrous cycle your cat 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?
The treatment of infertility depends upon the results obtained during the diagnostic workup and the resulting diagnosis. Ovarian cysts or tumors may require surgical excision, hormonal imbalances may need to be corrected, and infections will require treatment.
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, and 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.
Work with your veterinarian to determine the best course of action for your cat.
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