Can a pregnant cat go into heat: What does the science say

If you’ve found your way to this article, chances are you’re grappling with an unexpected scenario: your pregnant cat seems to be exhibiting signs of heat once more. It’s a puzzling situation. Believe me, if you’re pondering whether can a pregnant cat go into heat, you are not alone.

If you do a Google search, you’ll find many contradictory answers. Sadly, most of the authors have no medical background. And while some of the results might be good, most of those I found were wildly misleading 😩

There are several reasons why your cat is behaving this way. Let’s take a look at the science and the physiology of feline reproduction. By giving you medicaly accurate information, I want to help you understand what’s happening with your beloved kitty. 

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While I am a veterinarian, this article is not intended to replace professional veterinary advice. If you have any medical concerns about your pet, consult your vet immediately. Always seek professional assistance if you are unsure of your pet’s health.

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Understanding a cat’s reproductive cycle

The feline estrous cycle, also known as the heat cycle, plays a pivotal role in a cat’s reproductive behavior. This cycle is a recurring process that prepares a female cat for potential mating and pregnancy. It consists of several distinct phases, each marked by specific physiological and behavioral changes.

Cats are so-called induced ovulators, which means ovulation is stimulated by mating. It was previously believed that cats don’t ovulate unless they mate with a male. However, now we know that it’s not always the case. There are instances where cats can ovulate without the need for mating. This phenomenon is mostly often observed in situations where female cats coexist with male cats within the same household.

Yes, cats are complicated…🤷‍♀️

A cat in heat is in the fertile period of her reproductive cycle and is attracted to intact male cats.

An unspayed female cat will have her first heat cycle when she reaches puberty. This usually occurs at around 6 months of age, but it can vary individually.

While this means she reached sexual maturity, it definitely doesn’t mean that she’s ready to become a mother cat. A cat shouldn’t have her first litter of kittens until she’s fully mature. For some cat owners, this might mean waiting with mating until the cat is 24 months old.

Cats have multiple cycles during their breeding season. In the Northern Hemisphere, the mating season runs from March to September, while in the Southern Hemisphere, it’s from around September to March. And some indoor cats may even have their cycle all year round. 

Phases of the oestrus cycle:

1. Proestrus

Proestrus is the initial phase of the estrus cycle. During this phase, female cats begin to exhibit subtle signs of being in heat. These signs may include increased vocalization, restlessness, and heightened attention to male cats. However, they are not yet receptive to mating. Proestrus typically lasts for 1-2 days.

1. Estrus

Estrus is the most recognizable phase of the estrus cycle, commonly referred to as “heat.” During estrus, female cats become sexually receptive and engage in mating behaviors with male cats.

The most notable signs of estrus include increased affection towards male cats, raising the hindquarters when petted, and vocalizing more frequently. Estrus typically lasts for about 4-7 days, but it can vary.

1. Metestrus

Metestrus is a brief phase that follows estrus. If the female cat does not mate during estrus, she will enter metestrus. During this phase, she becomes less receptive to mating, and her behavior gradually returns to normal. Metestrus usually lasts 1-2 days.

1. Anestrus

Anestrus is the longest phase of the estrous cycle and is marked by a period of sexual inactivity. Female cats in anestrus do not display signs of being in heat and are not receptive to mating. The duration of anestrus varies but can last for weeks to several months. 

It’s important to note that the duration of each phase can vary from cat to cat. Factors such as age, breed, and environmental conditions can influence the length of each phase. Did I already mention that cats are complicated? ☺️

Role of hormones in the reproductive cycle

Hormones play a crucial role in regulating a cat’s estrous cycle. Two primary hormones, estrogen and progesterone, orchestrate the physiological changes that occur during each phase.

Estrogen:

Estrogen is a hormone responsible for the changes observed during proestrus and estrus. 

The main hormone responsible for sexual behavior is estradiol.

Estradiol triggers the following effects:

• Attracting males
• Signs of heat
• Receptive behavior
• Physical changes during the heat

Progesterone:

Progesterone, on the other hand, becomes prominent during metestrus and anestrus. 

It is produced by corpus luteum (a structure in ovaries, that develops after the eggs are released). If the cat is pregnant, progesterone is also produced by the placenta. This is important – a pregnant cat is under the influence of progesterone, which is necessary for maintaining the pregnancy. 

It has several effects, including:

• Preparation of the uterus: Progesterone prepares the uterine lining for potential pregnancy.
• Maintaining pregnancy: If mating occurs and fertilization is successful, progesterone is vital for maintaining the pregnancy.
• Inhibition of estrus behaviors: Progesterone suppresses estrus behaviors when the cat is not in heat.

Understanding the interplay of these hormones in the feline estrous cycle is essential for comprehending a cat’s reproductive behavior and the factors that can influence it.

You can say that a cat is under the influence of either estrogen or progesterone during her cycle, and each hormone affects her differently. 

Cat pregnancy: a journey into feline maternity

Understanding the fundamentals of cat pregnancy is essential to ensure the well-being of your expectant feline friend and her developing litter.

The gestation period, or length of pregnancy, in cats typically spans roughly two months. This period is counted from the day of successful mating to the day of birth and usually falls within the range of 63-65 days, although it can vary slightly.

Signs of pregnancy in cats:

Cats, like humans, go through various physiological changes during pregnancy. Here are some common signs and symptoms to look for:

• Changes in appetite: Some cats may exhibit changes in their appetite. They may become more finicky or, conversely, have an increased appetite. She should have plenty of high-quality food and a constant access to fresh water.
• Notable weight gain: Well, obviously, pregnant cats gain weight as their pregnancy progresses 😃
• Nesting behavior: Pregnant cats often exhibit nesting behavior, where they create a comfortable spot to give birth. You can offer her a nesting box, but the changes she might use it are about 50:50. Cats tend to find their own quiet place when they feel their due date is approaching. 
• Abdominal enlargement: As the pregnancy advances, you’ll notice a gradual enlargement of your cat’s abdomen.
• Mammary gland changes: The mammary glands will become larger and firmer in preparation for nursing the kittens.
• Behavioral changes: Your pregnant kitty might show affectionate behavior, but she can also become more withdrawn. 
• Morning sickness: Some unfortunate kitties may experience morning sickness
• Increased water consumption: Pregnant cats may drink more water than usual to support the developing kittens.

Pregnancy diagnosis:

Feline pregnancy is a multifaceted process that requires careful observation and management. An early diagnosis is crucial for every cat breeder. After all, we’re all eager to confirm the success of the breeding, aren’t we? 😊

Furthermore, it’s necessary to rule out false pregnancy (commonly known as phantom pregnancy, or pseudo-pregnancy), and check for signs of any underlying health concerns. 

So, what are the primary diagnostic methods employed in veterinary medicine to identify feline pregnancy?

• Abdominal palpation: Embryos and their protective sacs form small swellings in the uterine horns. These tiny swellings are palpable ~21 – 25 days after fertilization. Well, that is if your kitty is feeling cooperative 😊
• Relaxin test: Relaxin is produced by the placenta. Relaxin test can be used after 25-30 days of gestation to determine if pregnancy exists. 
• Ultrasound: Ultrasound is a non-invasive and safe method for checking the presence of fetuses. It provides a visual image of the developing babies and can be used to assess the viability of fetuses. Ultrasound is especially useful for early detection.
• Radiography: Digital X-rays are usually taken later in a cat’s pregnancy after bones in the fetuses are sufficiently developed to show on the image. Late pregnancy radiography is the best method for estimating the number of kittens.

Hormonal influences and changes during heat and pregnancy

Understanding the hormonal influences and changes that occur during a cat’s heat cycle and pregnancy is essential for comprehending their reproductive behavior and the physiological adjustments that take place.

Hormonal changes during heat (Estrus)

Estrogen Dominance: During the estrus phase of the feline reproductive cycle, estrogen plays a dominant role. Increased levels of estrogen trigger various changes and are responsible for the typical mating behavior.

Luteinizing Hormone (LH): LH surges in response to rising estrogen levels. This surge triggers ovulation, where mature eggs are released from the ovaries. It’s during this surge that the cat is most fertile and receptive to mating.

Hormonal changes during pregnancy

Pregnancy brings its own set of hormonal changes and influences, which are essential for supporting the growth and development of the kittens.

Progesterone Dominance: Progesterone takes center stage during pregnancy, maintaining the uterine environment for the growing embryos. Key roles of progesterone during pregnancy include:

• Maintaining the uterus: Progesterone helps ensure that the uterus remains receptive and supportive for implantation and the development of fetuses.
• Inhibition of estrus behaviors: Progesterone suppresses estrus behaviors during pregnancy.

Prolactin: Prolactin, another hormone, increases as pregnancy progresses. It is responsible for preparing the mammary glands for milk production, ensuring that the kittens will have nourishment after birth.

Relaxin: Relaxin is produced by the placenta. During the latter stages of pregnancy, relaxin levels increase. This hormone relaxes the ligaments and cervix to facilitate the birth process.

Understanding these hormonal changes is not only fascinating but also crucial for recognizing the physiological needs of a pregnant cat and the behavioral changes associated with heat. 

It’s important to remember that a cat in heat and a pregnant cat will exhibit very different behaviors and hormonal profiles due to these significant hormonal shifts. 

So if you look at the physiology, a pregnant cat is under the influence of progesterone, which inhibits mating. So what is going on with your cat? 

Let’s look at some possible explanations:

Can a pregnant cat go into heat?

Pregnancy in cats is typically marked by distinct hormonal changes and behavioral shifts. However, rare occurrences may lead to confusing situations where a pregnant cat appears to go into heat.

First, let’s talk about the instances where the cat really goes (or is) in heat:

1. Very early stages of pregnancy

Fertilized eggs typically implant themselves in your cat’s uterus at the later stages of the second week of pregnancy. Your cat’s estrus cycle may persist during this time, and if she mates again, it could result in kittens from different males. 

So during the first days of pregnancy, your cat might show signs of heat. 

So yes, technically a cat can still be in heat while already pregnant during the first days of pregnancy.

Btw. having kittens from different fathers is a common occurrence in cats, it’s called superfecundation. 

2. Pseudopregnancy

Pseudopregnancy, also known as “false pregnancy” or “phantom pregnancy,” is a condition in which a non-pregnant female cat exhibits signs and behaviors similar to a pregnant cat. A pseudopregnant cat can display nesting behaviors, abdominal enlargement, and even lactation. 

Pseudopregnancy can be confused with actual healthy pregnancy due to its resemblance to the real thing. It’s typically caused by hormonal imbalances and can be diagnosed using an easy ultrasound test.

You might be convinced that your cat is pregnant (and she’ll feel that way too). But suddenly, she starts to exhibit mating behavior again. The reason might be that she wasn’t pregnant at all…

3. Superfetation

Superfetation refers to an additional conception occurring while a pregnancy is already in progress. 

This phenomenon involves the presence of offspring at significantly varying stages of development within the uterus.

Now this is the problematic part. True superfetation does exist in some mammals (for example American mink or Europen badger). 

However, superfetation has not been conclusively confirmed to occur in domestic cats. Despite occasional case reports suggesting the coexistence of kittens of different ages in pregnant queens, we still lack concrete evidence for this phenomenon in felines.

The reports usually mention the discovery of offspring with varying levels of development within the uterus upon post-mortem examination or after birth. However, these reports can be explained as arrested development or developmental pathologies. 

This means that if you have 5 kittens, 3 are born normal and 2 are small and underdeveloped, chances are there was a problem during pregnancy and those small babies didn’t develop properly. Not that they were conceived later in the pregnancy. 

If you want to learn more about this interesting phenomenon, have a look at references 🙂

Why is a pregnant cat acting like she’s in heat?

Usually, cats behave differently during pregnancy than they do when they are in heat. However, it’s been shown that in some cases, cats can act as if they are in heat even during pregnancy. 

This is important, they act as if they are in heat, but they are not.

In some instances, pregnant cats might exhibit heat-like behaviors due to hormonal imbalances. These imbalances can disrupt the typical hormonal profile of pregnancy, leading to the display of estrus behaviors. 

Additionally, the presence of unspayed adult males can cause her to act as though she is in heat. 

If a pregnant cat continues to display estrus-like behavior over an extended period it is advisable to consult a veterinarian, as it may indicate an underlying issue or a problem during her pregnancy that requires attention. 

What to do if your pregnant cat is acting like she’s in heat

First of all, you need to be sure she really is pregnant. Take your furry friend to the vet for a pregnancy check-up. The veterinarian will conduct a physical examination and may also use ultrasound or X-rays to assess the cat’s condition. 

Your vet can use a relaxin test, palpation, or ultrasound / X-rays for pregnancy confirmation. 

If your cat was in heat and mated very recently, she might already be pregnant but can be willing to mate again. It’s too early in her pregnancy and she’s still basically in heat. 

If you have an unneutered male cat in your home, continue to observe your cat. She might be stimulated by him, but as her pregnancy progresses, this behavior should change. 

If your cat is acting like she’s in heat for an extended period, take her to a vet. She needs to be examined to be sure there are no underlying health issues. 

Please always follow your vet’s specific recommendations. 

I hope this helped you understand this complicated issue. Trust your instincts. You know your pet, if you feel that something is not right, it’s always a good idea to take her to a vet. 

I wish you good luck and many healthy kittens 🥰

PS: If you are as crazy about animals as I am and want to get more pet health tips, subscribe to my newsletter! Now you will get a free pet planner as a bonus 🤗

References:

• Roellig K, Menzies BR, Hildebrandt TB, Goeritz F. The concept of superfetation: a critical review on a ‘myth’ in mammalian reproduction. Biol Rev Camb Philos Soc. 2011 Feb;86(1):77-95. doi: 10.1111/j.1469-185X.2010.00135.x. PMID: 20394608.
• Tsutsui T, Stabenfeldt GH. Biology of ovarian cycles, pregnancy and pseudopregnancy in the domestic cat. J Reprod Fertil Suppl. 1993;47:29-35. PMID: 8229938.
• Holst BS. Feline breeding and pregnancy management: What is normal and when to intervene. Journal of Feline Medicine and Surgery. 2022;24(3):221-231. doi:10.1177/1098612X221079708