What you should know about phantom pregnancies

It is estimated that around 80% of intact females experience phantom pregnancies, and yet there are so many misconceptions about how this condition manifests, how it impacts dogs and how it should be managed. This blog is going to examine some of the lesser-known facts regarding phantom pregnancies and how you can support your dog.

Phantom pregnancies (also known as pseudo-pregnancy, or pseudocyesis), is a condition which causes a female to imitate the physical and behavioural symptoms of pregnancy. 

Phantom pregnancies occur at the third part of the cycle around 6-12 weeks after oestrus, (once the vulva has shrunk) during the Diestrus/metoestrus stage and can begin on a female’s first heat. Prolactin is a hormone in mammals that enables them to produce milk. During the metoestrus stage, levels of prolactin increase as progesterone levels decrease, consequently resulting in mammary enlargement and milk production in some dogs.

 The initial signs of a phantom pregnancy usually manifest behaviourally, such as mothering items and becoming aggressive when touched or approached. Resource guarding is also a common issue, thus it’s important to keep the dog separate and limit interactions with young children and other pets in the home during a phantom pregnancy. If the dog is experiencing an overt phantom pregnancy, clinical signs will be obvious, such as a swollen abdomen, weight gain and swollen mammary glands that may or may not produce milk. Other symptoms can include restlessness, vomiting, lethargy and anxiety. It’s important to note that not all dogs experiencing phantom pregnancies will actually experience any or all of these symptoms. Many dogs do not experience any of the physical symptoms and may only display sudden behavioural changes, like anxiety and aggression. This is often known as covert or silent phantom pregnancy. In fact, a UK survey designed to examine the current diagnosis and treatment of phantom pregnancies, revealed that 96% of vets reported observing behavioural changes in pseudo-pregnant bitches without any physical changes. 97% of vets also observed aggression in pseudo-pregnant bitches.  (Amanda L Root et al 2018)

 Understandably, many guardians may not recognise that the changes they are seeing are due to a phantom pregnancy, especially if they do not track their dog’s cycle. It is now believed in the veterinary community that all bitches experience phantom pregnancies to some degree, because all experience the increase in prolactin levels, however, any physical or behavioural changes may be extremely subtle.  Symptoms of a phantom pregnancy can persist for 4-8 weeks, however, they usually dissipate within 2-3 weeks

Many guardians will spay their dog to prevent phantom pregnancies, however, studies show this isn’t always effective in preventing them. The same survey, mentioned above, revealed that 49% of vets reported phantom pregnancies in spayed bitches. (Amanda L Root et al 2018) This is likely due to many dogs being spayed at an inappropriate time in their cycle. If a dog is spayed when the prolactin levels are still too high, this can cause a ‘Persistent Phantom Pregnancy’ (PPP). This means that the prolactin levels do not drop and the physical and/or behavioural symptoms can become permanent unless treated. Sadly, many dogs can become aggressive and bite if they are spayed during a phantom pregnancy, but if the vet doesn’t inform the guardian and/or the dog doesn’t experience the obvious symptoms, the dog can be ultimately euthanised. Dogs can experience phantom pregnancies days after their spay, however, it is more common to occur weeks or even years later. This means dogs can suddenly develop anxiety or aggression months or years after their spay, without anyone pinpointing the cause.

It is currently unknown how many dogs lose their lives due to aggressive behaviour triggered by persistent phantom pregnancy, but it is believed to be extremely common; so much so it is now known as the ‘silent killer’.  This situation is completely preventable by tracking the dog’s cycle carefully, spaying only when both physical and behavioural symptoms have subsided and treating the phantom pregnancy with medication to decrease the prolactin levels. Vets recommend that dogs should be spayed 4 months after their last day of oestrus to allow the prolactin levels to drop and prevent a persistent pregnancy, however, a dog may still be inadvertently trapped in a persistent phantom pregnancy, even when spayed after this length of time. 

In some cases, spaying during proestrus may be the safest option, if phantom pregnancies are continuous, however, the vet would need to do the surgery laparoscopically (keyhole) due to the bleeding risk. Some may decide that they want to spay their dog before she reaches her first season, since a dog cannot enter a phantom pregnancy without ovulating before or experiencing metoestrus (Harvey et al 1999), however, the health risks of doing this are significant. Many studies show a range of breeds are at an increased risk of hip dysplasia, cranial cruciate ligament injury, urinary incontinence and many cancers, such as lymphosarcoma, hemangiosarcoma and mast cell tumor, when spayed before one year of age. (Benjamin L Hart et al 2014) (Gretel Torres de la Riva, Benjamin L. Hart et al 2013) (Ware & Hopper 1999). Spaying dogs during adolescence ( a development stage that can last between 6 months to 3 years of age) can also stunt the growth of the brain and make adolescent behaviours permanent, even when they reach adulthood. Therefore, spaying a female before 6 months or 1 year of age, comes with risks far greater than those posed by phantom pregnancies and isn’t recommended from a health or behavioural standpoint.

If your dog suffers with regular phantom pregnancies, your vet can prescribe cabergoline. This is licensed for use for 4-6 days and can be effective in stopping the phantom pregnancy, however, symptoms can return within 1-4 weeks. This will require further treatment of cabergoline for 14 days, although this has to be prescribed off-license since the treatment has only been tested for 4-6 days. This can be prescribed even after a dog is spayed if behavioural or physical symptoms of a phantom pregnancy persist. Thankfully it is usually effective in reducing anxious or aggressive behaviours, provided it is directly caused by a persistent phantom pregnancy. It is a myth that phantom pregnancies will just resolve on their own, so its important to seek veterinary care if your dog is suffering.

Allowing dogs to perform mothering and nesting behaviours can also prolong a phantom pregnancy. Studies show that behaviours such as creating a den and mothering objects and toys is observed in around 96% of bitches. Mothering objects or toys and licking the nipples can maintain levels of prolactin and encourage milk production, so it’s important to temporarily and carefully remove any items the dog is mothering and prevent them from licking by using a buster cone, inflatable collar or a onesie. Neglecting to do so can result in a persistent phantom pregnancy and even mastitis, which is a painful inflammation of the mammary glands.

If you are concerned your dog is suffering with phantom pregnancies, regardless of neuter status, it is important to speak to your vet and explore treatment options, particularly when anxiety and aggression are involved.

Take away points 

• Every bitch experiences a phantom pregnancy to some degree

• Not all dogs experience physical symptoms, such as swollen nipples or lactation

• Spaying during a phantom pregnancy is dangerous and can lead to a persistent phantom pregnancy and even behavioural euthanasia. 

• Spaying is not always curative if it is done at the wrong point in the dog’s cycle.

• Females should be spayed 4 months from the last day of oestrus.  

• Mothering, licking the nipples and nesting behaviours can maintain levels of prolactin prolonging the phantom pregnancy. 

• Phantom pregnancy can trigger resource guarding, anxiety and aggression. 

• Cabergoline can be prescribed for 4-6 days to treat phantom pregnancies, however, it may be needed for 2 weeks, especially in anxiety and aggression cases

As dog professionals it is imperative, that we understand the behavioural impact of phantom pregnancies and the consequences of spaying during this stage of the cycle, in order to recognise the condition, even in its most subtle presentation, and educate dog guardians as much as possible. Doing so, could save the lives of many dogs.

References

Root AL, Parkin TD, Hutchison P, Warnes C, Yam PS. Canine pseudopregnancy: an evaluation of prevalence and current treatment protocols in the UK. BMC Vet Res. 2018 May 24;14(1):170. doi: 10.1186/s12917-018-1493-1. PMID: 29793494; PMCID: PMC5968611 Canine pseudopregnancy: an evaluation of prevalence and current treatment protocols in the UK - PubMed (nih.gov)

Davies. S, 2023, Pseudopregnancy in spayed bitches- a preventable welfare problem. Improve Veterinary Practice, Pseudopregnancy in spayed bitches – a preventable welfare problem - Veterinary Practice

Gretel Torres de la Riva, Benjamin L. Hart , Thomas B. Farver, Anita M. Oberbauer, Locksley L. McV. Messam, Neil Willits, Lynette A. Hart, 2013, Neutering Dogs: Effects on Joint Disorders and Cancers in Golden Retrievers Published: February 13, 2013https://doi.org/10.1371/journal.pone.0055937

Hart BL, Hart LA, Thigpen AP, Willits NH. Long-term health effects of neutering dogs: comparison of Labrador Retrievers with Golden Retrievers. PLoS One. 2014 Jul 14;9(7):e102241. doi: 10.1371/journal.pone.0102241. PMID: 25020045; PMCID: PMC4096726.

Hart BL, Hart LA, Thigpen AP, Willits NH. Assisting Decision-Making on Age of Neutering for Mixed Breed Dogs of Five Weight Categories: Associated Joint Disorders and Cancers. Front Vet Sci. 2020 Jul 31;7:472. doi: 10.3389/fvets.2020.00472. PMID: 32851043; PMCID: PMC7412743.

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Hart, B.L., Hart, L.A., Thigpen, A.P. and Willits, N.H. (2016), Neutering of German Shepherd Dogs: associated joint disorders, cancers and urinary incontinence. Vet Med Sci, 2: 191-199. https://doi.org/10.1002/vms3.34

Harvey MJ, Dale MJ, Lindley S, Waterston MM. A study of the aetiology of pseudopregnancy in the bitch and the effect of cabergoline therapy. Vet Rec. 1999 Apr 17;144(16):433-6. doi: 10.1136/vr.144.16.433. PMID: 10343374.