Infertility in Female Cats

What is infertility?

Infertility in a female cat is defined as the inability to conceive and give birth to live kittens, despite appropriate breeding with a fertile male.

What is the normal heat cycle in a cat?

Female cats normally begin to have estrous (heat) cycles at 4 to 12 months of age, with the average onset at six months of age. The first heat cycle may occur as late as 18 months of age in longhaired or larger breeds. 

Heat cycles in cats are influenced by daylight, typically requiring 14 or more hours of natural or artificial light to occur. For this reason, cats in the Northern Hemisphere typically cycle from January through October and may not cycle in the fall and winter months.

There are several stages in the estrous cycle. Estrus is the stage when the female cat is in heat, or sexually receptive. In cats, ovulation must be induced, which means that they will not ovulate unless mating occurs. If the cat mates during estrus, a surge of luteinizing hormone triggers ovulation — the release of eggs from the ovary. Once this occurs, estrus will typically end within one to two days.

What causes infertility in female cats?

Fertility problems in female cats can be grouped into four broad categories: abnormal heat cycles, failure to mate, failure to conceive, and pregnancy loss.

What causes abnormal heat cycles?

Cats may have abnormal heat cycles or fail to cycle. A female cat that never has a first heat cycle may have hereditary or genetic conditions, such as: chromosomal abnormalities, hermaphroditism (male and female sexual organs), or abnormal uterine or ovarian development.

Abnormal cycles may also be caused by environmental stress, medications, or inadequate daylight. Additionally, ovarian cysts and tumors may interfere with the cat’s heat cycles by releasing hormones.

What causes failure to mate?

A failure to mate is often attributed to abnormalities or traumatic injuries to the reproductive tract. Both factors can physically prevent mating or make it so painful that the female is unwilling to mate. 

Immature or inexperienced cats may fail to mate. Other factors thought to contribute to mating failure include behaviors like stress or aggression, lack of teeth, mouth pain, breed-related low libido, or female preference.

What causes failure to conceive?

Pyometra is a serious uterine infection in which the uterus becomes inflamed and filled with bacteria.A female cat may fail to conceive for several reasons:

• Mating too few times 
• Mating too early or too late during estrus
• Incomplete mating
• Failure to ovulate despite mating sufficiently
• Infection of the uterine lining (endometritis) 
• Abnormal mucous production in the uterus (mucometra)
• 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 prevent implantation or cause pregnancy loss. These infections include feline leukemia virus (FeLV), feline immunodeficiency virus (FIV), calicivirus, panleukopenia, herpesvirus, or bacterial infections.

What causes pregnancy loss?

Pregnancy loss may have several causes, including:

• Inadequate reproductive hormones
• Malnutrition or severe illness
• Certain medications (e.g., corticosteroids) may lead to fetal death.
• Infections including E. coli, Mycoplasma spp., Salmonella spp., Toxoplasma gondii, feline leukemia virus, and feline herpesvirus 1 
• Environmental stress
• Fetal chromosomal abnormalities

How will my veterinarian determine the cause of my cat’s infertility?

Your veterinarian will begin with a complete physical exam. The findings will help guide further testing. Tests may include:

• Blood and urine tests. Screening blood work, including thyroid levels, can be used to assess your cat's overall health and identify possible causes of infertility. A urinalysis may also be performed to check for urinary tract disease, as the urinary and reproductive tracts are related.
• Infectious disease testing. FeLV and FIV are common causes of feline infertility, so your veterinarian will likely test your cat for these conditions. Your veterinarian may test for other infectious diseases depending on your cat’s clinical signs and history.
• Hormone tests. Measuring blood levels of progesterone and estradiol can help your veterinarian identify the stage of your cat’s heat cycle.
• Vaginal cytology and culture. Your veterinarian will take a swab from your cat’s vagina for examination under a microscope. The types of cells present help identify the stage of your cat’s heat cycle. A sample of vaginal material may also be submitted for bacterial culture, to assess for infection.
• Imaging. X-rays or ultrasound may reveal abnormalities in the abdomen.

How is infertility treated?

The treatment of infertility depends on the cause. Ovarian cysts or tumors may require surgical removal, hormonal imbalances may need to be corrected, and infections will require treatment.

Improving daily care and breeding conditions may also help. All breeding female cats should receive at least 14 hours of daylight per day and should be allowed to breed several times per day during estrus.

Regardless of fertility status, all breeding female cats should be provided with a clean, low-stress environment and a high-quality, well-balanced diet. Ensure that your cat receives enough food and avoid overcrowding and other sources of stress.

Work with your veterinarian to determine the best course of action for your cat.