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Cat Birth Defects

Updated on: July 20, 2021
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It’s relatively common for cats to be born with birth defects. These defects include abnormalities of function, structure, or metabolism that are present at birth. Many of these defects resolve on their own. But in some cases, they require medical attention to correct or they are present for the cat’s entire life.

Congenital defects in kittens tend to be rare. Some research has shown pedigreed cats have a higher risk of developing a defect. However, the risk is statistically insignificant. Defects don’t seem to affect one specific breed over another.

Cat Birth Defects

Defects can cause physical impairment and in some cases, serious defects are fatal

Birth defects might be obvious at birth, subtle and apparent only when the cat doesn't develop properly. Some are detected when cats start showing clinical signs of a health problem or found only with diagnostic testing. Other problems, like a heart defect, are diagnosed later on.

What are some of the defects cats are at risk for?

Blood Type Incompatibility

It’s dangerous for cats with different blood types to breed. If a blood type B female cat breeds with a blood type A male cat, the litter is at risk of dying shortly after birth. This is due to the incompatibility which destroys red blood cells in the kitten.

Cleft Palate

Cleft palate occurs when kittens are born with an opening in the roof of their mouths due to the two sides never fusing. Many cat owners wouldn’t think to look inside the top of their cat’s mouth.  Cleft palate is often discovered due to the condition’s corresponding symptoms, which include coughing, runny nose, and difficult nursing.

Cleft palate is usually inherited. Some breeds are more prone to it than others, including:

  • Siamese
  • Ragdolls
  • Norwegian forest cats
  • Ocicats
  • Persians
  • Savannahs

Exposure to certain chemicals, cortisone, medications, or excessive intake of vitamins A and D during pregnancy also puts kittens at risk of cleft palate.

Flat Chested Kitten Syndrome (FCK)

Flat Chested Kitten Syndrome causes a kitten to develop a depression in the rib cage because of a collapsed lung.


Also known as water on the brain, hydrocephalus causes cerebrospinal fluid (CSF) to accumulate around the brain or blocks CSF from flowing outward, which leads to pressure around the brain. Kittens usually develop hydrocephalus because of CSF blockage. However, other causes of hydrocephalus in cats include:

  • Certain viruses
  • Bacterial and fungal infections
  • Parasitic migration
  • Cysts and tumors

Hypertrophic Cardiomyopathy

Cardiomyopathy is heart disease in cats that usually leads to heart failure. Among all the other forms of congenital heart defects, hypertrophic cardiomyopathy is the most common. This condition is characterized by the walls of the heart becoming too thick. Congenital heart disease such as this can sometimes result in death.

Intestines on the Outside of Body

Kittens born with their intestines or any other organ exposed should undergo veterinarian examination immediately. In some cases, surgery can correct the defect.


Some kittens’ eyes are not grown to full size. With microphthalmia, the eyeball appears to be smaller than normal. In some cases, the eyeballs are absent. 

Open Fontanelle

The fontanelle is the soft spot on the top of the head that closes soon after birth. It is present in humans and animals alike. The soft spot allows the plates of the skull to move so the baby’s head can pass through the birth canal. It usually seals on its own within a few days or weeks of birth, but if it does not, it leaves the brain exposed to risk.

Pectus Excavatum

Some kittens are born with this unusual chest wall deformity. It’s sometimes called an inverted sternum. It is said to be caused by genetics. However, pectus excavatum has a tendency to develop spontaneously regardless of the cat’s breed. The condition is often diagnosed several weeks after birth, or earlier if it is severe.


This is a potentially fatal bacterial infection that affects kittens two weeks and younger. If left untreated, septicemia could progress to a severe form which can then lead to liver failure, respiratory distress, kidney failure, and more.

Swimmer Syndrome

Swimmer syndrome occurs when a kitten cannot crawl or stand normally. The kitten’s hind legs are typically splayed laterally. They display what is called a frog-like posture.

Umbilical Hernia

This is the most common type of kitten hernia and occurs at the belly button. This occurs because the umbilical ring failed to close fully. The hernia presents as a protrusion under the cat’s skin especially when the cat is straining, crying, meowing, or standing.

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What Causes Birth Defects in Cats?

Most of the birth defects in cats have no known cause. Experts say these are brought about by two main causes

Some congenital defects associated with cats are said to be caused by genetic factors coming from mutated genes or chromosomal abnormalities. 

Other birth defects may also be caused by environmental factors - exposure to toxins, viral infections during pregnancy, nutritional deficiencies, and many more. Taurine deficiencies are especially problematic for cats. 

On another hand, a congenital defect might come from a combination of two or more of these factors.

Are Cat Birth Defects Preventable?


There are things breeders can do to reduce the risk of kitten birth defects. Cats can now undergo genetic tests to prevent birth defects.

Basepaws can test your cats before breeding to determine if there are any genetic risks that are of concern. It’s more difficult to prevent birth defects when you don’t know the genetic history of a cat.

To reduce the risk of birth defects, consider the following before allowing your cat to mate:

  • Is your cat’s particular breed make-up prone to birth defects?
  • Was your cat born to a litter with one or more defects, even if it does not have a defect?
  • Has your cat mated before and experienced any issues?
  • Is there anything impeding your ability to provide your cat with a healthy diet and environment once she’s pregnant?
  • Is your cat taking any drugs?
  • Is your cat up-to-date on vaccines and will any vaccines be needed during pregnancy?

Consider a thorough health examination by a veterinary healthcare professional before breeding your cat, even if you know of no potential risks. An examination should occur before every breeding experience.

Cat Birth Defects 1

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The Definitive Guide to Cat DNA testing: What you need to know.



Lowell Ackerman DVM, DACVD. “Tufts’ Canine and Feline Breeding and Genetics Conference, 2005.”, 30 Mar. 2015, Accessed 31 Jan. 2021.

CDC. “Learn about Specific Birth Defects.” Centers for Disease Control and Prevention, 5 Aug. 2019,

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