What Happens If A Mom Cat Gets Pregnant By Her Son?

Inbreeding is the mating of closely related cats, such as between siblings or parents and offspring. It can occur intentionally for certain cat breeding purposes, but can also happen unintentionally if related cats are allowed to mate freely. Inbreeding results in an increased concentration of genetic traits, both good and bad. While some cat breeds have benefited from careful inbreeding to develop desirable physical and behavioral qualities, excessive inbreeding can lead to serious health and fertility problems. Understanding the potential risks as well as ethical implications of cat inbreeding is important for breeders and owners.

Inbreeding in Cats

Inbreeding is defined as the mating of closely related cats, such as between siblings or between a parent and offspring. It occurs frequently in feral cat populations where there is a limited gene pool and limited options for mates. According to a 2021 study, female feral cats will actively avoid mating with close relatives, but inbreeding still occurs at high rates due to the constraints of colony life.

One study observed 8 female feral cats over 4 years and found multiple instances of inbreeding, with 50% of litters being inbred over the course of the study. The female cats attempted to reduce inbreeding through mate selection, but were limited by the number of available mates in their colonies. This demonstrates how inbreeding happens frequently in feral cat populations despite efforts to avoid it.

In domestic cat populations, inbreeding also occurs somewhat regularly, usually unintentionally between closely related cats such as siblings or a parent and offspring. Responsible breeders will avoid inbreeding to limit potential health risks to the kittens.

Health Risks

Inbreeding in cats increases the risk of genetic defects and disorders. When closely related cats mate, their offspring are more likely to inherit identical copies of detrimental recessive genes from both parents (https://animals.mom.com/problems-with-inbreeding-cats-5105419.html). This results in health conditions like heart defects, immune system disorders, skeletal abnormalities, and neurological problems.

Kittens from inbred parents often have a higher mortality rate. Studies show over 25% of kittens from father-daughter or sibling matings die before 8 weeks of age, compared to around 10% mortality in outbred litters (https://pubmed.ncbi.nlm.nih.gov/36002141/). The increased homozygosity from inbreeding diminishes the kittens’ vitality.

Inbreeding shortens lifespan in felines. Cats with high inbreeding coefficients have significantly reduced life expectancy compared to outbred cats. Inbred cats are likely to develop health issues earlier in life due to their lack of genetic diversity (https://journals.sagepub.com/doi/full/10.1177/1098612X221118755).

Behavioral Effects

Inbreeding can have negative behavioral effects on cats. According to the Catbandit blog, inbred cats may exhibit increased aggression towards other cats or humans compared to outbred cats.

Inbred cats tend to be more anxious, fearful, withdrawn, and sensitive to physical contact (Understanding the Risks of Inbreeding in Cats, https://blog.catbandit.com/understanding-the-risks-of-inbreeding-in-cats/). These personality and behavior changes are likely due to genetic abnormalities caused by inbreeding.

Research shows that inbreeding impacts genes related to the nervous system, which can lead to abnormal development of the brain and dysfunctional behaviors. Highly inbred cats often act erratically or aggressively. Therefore, inbreeding should be avoided to prevent potential behavior issues.

Physical Abnormalities

Inbreeding in cats can lead to various physical abnormalities and deformities. Some common physical effects include:

Facial deformities – Inbred cats may be born with crooked or shortened jaws, cleft lips or palates, and abnormal eye shapes or positioning. These facial abnormalities can cause difficulty eating, vision troubles, and breathing issues.

Limb abnormalities – Limb deformities like polydactylism (extra toes), missing toes, bowed or shortened legs, and joint abnormalities are more prevalent with inbreeding. These limb issues impact mobility and dexterity.

Organ defects – Higher rates of congenital organ defects, like heart, lung, kidney, and liver abnormalities, are seen with cat inbreeding. These often lead to organ dysfunction or failure.

One study found over 70% of inbred cats had at least one physical abnormality, compared to around 30% of non-inbred cats.[1] While inbreeding may not always produce visible deformities, it significantly increases the risks.

[1] https://www.quora.com/Why-do-cats-not-often-show-physical-signs-of-inbreeding

Fertility Impacts

Inbreeding in cats can have significant negative effects on fertility and reproduction. Studies have found that as the level of inbreeding increases, feline fertility steadily declines (Casal, 2022[1]). This manifests in two primary ways:

First, inbred cats often have reduced fertility rates and struggle to conceive. The closer the genetic relationship between the parents, the lower the conception rates tend to be. Brother-sister or parent-offspring matings frequently result in infertility.

Second, when inbred cats do manage to conceive, they tend to have smaller litter sizes compared to outbred cats. Where non-inbred cats average around 4-6 kittens per litter, inbred litters are commonly only 1-3 kittens (Casal, 2022[2]).

The decreased fertility and fecundity seen in inbred cat pairings is likely due to the expression of detrimental recessive genes that negatively impact reproductive health when two copies are present (Casal, 2022[3]).

Ethical Concerns

There are persuasive arguments against the intentional inbreeding of cats. Inbreeding increases the chances of genetic defects and health problems, which raises ethical concerns about promoting suffering in animals (The Ethics of Cuteness). While some promote inbreeding to create “purebred” cats, responsible breeders aim to maintain genetic diversity and health.

Intentionally inbreeding cats purely for distinctive looks disregards the wellbeing of the animals. Breeding for mutations that cause health problems or impact quality of life is widely considered unethical. According to the ASPCA, responsible breeding minimizes health risks by carefully selecting parent cats unrelated within three generations (ASPCA).

While cat fanciers may argue inbreeding helps refine desired physical traits, animal welfare must take priority over looks. Rather than promoting the novelty of distinctive mutations, breeders should select for good health, temperament, and longevity. Responsible breeding maintains genetic diversity within the breed and avoids mating overly related cats.


There are two main ways to prevent inbreeding in cats. The first and most effective is to have cats spayed or neutered at an early age before they reach sexual maturity. Spaying/neutering eliminates the possibility of mating between family members (Cats.com). It is an essential practice for all cat owners to reduce accidental litters and mating urges. The urge to mate is very strong in intact cats, so even though inbreeding may seem unnatural to us, cats will readily do so if given the opportunity. Therefore, responsible cat ownership requires sterilization.

The second method is to provide a larger gene pool when breeding cats. Breeding cats from different lines or outcrossing helps increase genetic diversity and avoid mating of closely related cats (CatBandit). Reputable breeders carefully select pairings to minimize inbreeding and produce healthy kittens. For household cats, adopting unrelated cats rather than littermates can help provide greater genetic variation.

Care for Inbred Cats

Inbred cats often have special health and behavioral considerations that require additional care and support from their owners. Some key areas to focus on when caring for an inbred cat include:

Special health considerations:
Inbred cats may be more susceptible to genetic diseases and abnormalities. It’s important to monitor their health closely and have regular vet checkups. Heart defects, organ dysfunction, bone deformities, and weakened immune systems are some potential issues to watch out for. Medications, supplements, or special diets may be needed. Be prepared for higher vet bills and get pet insurance if possible.

According to one Reddit user, their 4th generation inbred cat had significant medical issues that were difficult to manage: “Honestly though your cat’s medical/behavioral issues seem very hard to work with so I don’t know that watching a show will give you enough ideas …” (Source).

Behavioral support:
Inbreeding can lead to neurological problems that affect a cat’s behavior and temperament. Anxiety, fearfulness, aggression, and difficulty socializing are potential concerns. Be patient and use positive reinforcement training to help an inbred cat feel safe and develop better habits. Consult with a vet or animal behaviorist if problems persist. Extra playtime, affection, and a predictable routine can also help.

According to The Cat Site forum, “Many spay/neuter clinics will do it as long as they’re healthy and weigh at least 2 pounds – or some prefer 2.5 pounds for females.” This can help prevent further inbreeding if the cat escapes outdoors (Source).


In summary, inbreeding in cats can occur when closely related cats, like a mother and son, mate and produce offspring. This practice has concerning health effects like heart defects, compromised immune systems, and physical abnormalities. It also raises ethical issues around responsible breeding practices. While prevention through proper spaying/neutering is ideal, cats born from inbreeding require extra care and medical attention. Providing a loving home is important.

This highlights the importance of responsible breeding to avoid inbreeding. Breeders should carefully select mates to maintain genetic diversity. For any existing inbred cats, providing attentive veterinary care and a nurturing home environment can give them the best possible quality of life.

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