Cats can get false pregnancies but they are much less commonly recognised than in dogs. There are some big differences between the species that make false pregnancies in cats tricky to spot while dogs show more obvious changes in behaviour. It’s important to know the signs to distinguish from a true pregnancy and to stop repeated false pregnancies from causing issues.
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What is a false pregnancy and how does it happen?
A false pregnancy, also known as a pseudopregnancy, is when the hormones of the non-pregnant female mimic those of pregnancy. Therefore, they can exhibit some signs of pregnancy such as mammary gland development and nesting.
To understand this more, let’s look at the stages of the reproductive cycle
After puberty, cats come into heat (the period when they are fertile and seeking a male) every two to three weeks in the breeding season. Some animals, like dogs (and humans!), spontaneously ovulate when in heat, meaning they release an egg (or more than one egg) from their ovaries whether they are mated or not. Conversely, cats mainly show induced ovulation. This means that the queen (an unneutered female) needs to be mated by a tom cat (an unneutered male) before their ovary releases an egg. This is one reason why false pregnancies are less common in cats as ovulation needs to occur to produce the hormones responsible.
However, cats are never that simple!
Studies have shown that at least one-third of queens do show near-spontaneous ovulation and, therefore, can have false pregnancies. The reasons for this are not known but the presence of a tom cat, close contact with other female cats and even stroking of your cat’s back are thought to possibly cause ovulation! Ovulation can also occur if mating occurs with an infertile male or through manual vaginal stimulation, called sham breeding, which is not recommended.
After an egg is released, a cyst-like structure called a corpus luteum is formed in the ovary which secretes progesterone, a hormone that is high during pregnancy. In a non-pregnant cat, this persists for about 40-45 days and then starts to disappear causing progesterone levels to drop.
What causes the signs of false pregnancy and what are they?
It is this decrease in progesterone that causes another hormone called prolactin to start to increase in pregnant cats and, to a much lesser extent, in cats with false pregnancies. Prolactin is responsible for mammary development, milk production and behavioural changes like nesting during pregnancy. In dogs, prolactin increases in the pregnant female and in non-pregnant females. This is the reason why dogs often have more obvious signs of false pregnancy than cats.
Cats often show no signs and owners only notice that their queen is not coming back into heat. Sometimes they do show signs associated with pregnancy; such as reddening of the mammary glands, known as ‘pinking-up’, where the nipples become more prominent. Occasionally, you may notice some mild nesting behaviour or milk production.
How do I know my cat is not actually pregnant!?
Cats are pregnant for around 65 days while pseudopregnancies usually only last around 45 days, although this can vary. Entire females can show minimal signs of pregnancy until the final trimester. And so it can be difficult in the first six weeks to differentiate between them. In the final trimester her abdomen will become noticeably more rounded and her behaviour may change. This includes change in appetite, nesting and being more affectionate. They can have some morning sickness, too.
Pregnancy can sometimes be diagnosed by your vet gently feeling the foetuses in the abdomen or, more reliably, from about three weeks post-mating they are big enough to be detected by ultrasound. Later in pregnancy, radiography can safely be used. But this has largely been superseded by ultrasonography, which is safe to use at any stage.
Does my cat need any treatment if they do have a false pregnancy?
As cats do not show significant signs of false pregnancy treatment is not usually required and it will resolve with time. If they do have repeated false pregnancies, it is best to consider neutering your cat. This is because the frequently high progesterone hormone can increase their risk of developing an infection in their womb, known as pyometra. This can be life-threatening and may need urgent surgery, so it is better to prevent this with neutering.
If you are not sure if your cat is having a false pregnancy, please contact your vet for help and guidance.
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