Categories: superfetation

What is feline superfetation?

Superfetation occurs when about 10 percent of cats come into heat when pregnant. This results in a second set of eggs being fertilised before the first litter is born. It is a result of the breeding capabilities of the domestic cat.

Normally pregnancy suppresses the sexual physiology of the female. However, female cats sometimes break the norms. There is another phase of sexual receptivity during the pregnancy cycle when there is a low level of pregnancy hormone.

The additional period of heat occurs around 3 or 6 weeks into pregnancy which lasts 9 weeks. This period of heat during pregnancy usually occurs between the 21st and 24th day. If the female mates again and her eggs are fertilised she’ll carry two litters at different stages of development.

The unborn kittens develop along side each other at different stages. When the female gives birth to the older kittens she may also give birth to the younger ones prematurely causing their death. If the younger ones go on to full term the mother will end up with too many kittens to fed as she’ll have a shortage of nipples 🙂 The mother normally finds a way to cope.

P.S. If your cat has experienced feline superfetation please share in a comment. Thanks.

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Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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  • I believe this just happened to my cat. At one point during her pregnancy she was acting like she was in heat again and the neighborhood Tom's were coming around again. She just gave birth and two of the kittens were stillborn and looked underdeveloped. One of them was born in a gush a fluid but its sac was fully intact with the placenta and everything. I had to struggle to break the sac as it was very thick. Neither kitten ever breathed or moved.

  • Thanks for writing about this Michael. I did not know that the two pregnancies could develop alongside each other. I am aware that females can have different fathers to each kitten in one litter, and they can hold a pregnancy in abeyance when times are hard, but this is a new, amazing fact for me. Truly incredible. Mother cats must be some of the most capable in the world.

    • Yes, it is all geared up for survival. The alternative is 'superfecundation' which is what you refer to.

  • Thank you for writing about this, Michael. I had never heard of this happening. I had no idea what the word 'superfetation' meant. Ten percent of pregnant cats coming into heat sounds like any awfully high rate of occurrence. The outcomes definitely sound unfavorable. 😧

    • It is a bit much. Cats are great survivors. I guess they have to be but it is not a good look.

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