What is phantom pregnancy in dogs?

Has your dog started acting like they are pregnant, mothering their toys and creating a nesting space? Have you noticed mammary development and even milk from their nipples? Some female dogs may display signs equivalent to morning sickness; with lethargy and dog vomiting. If your dog has not been mated, this may leave you scratching your head as to why they appear pregnant. If they have been mated, before you get too excited about visions of cute puppies, you need to make sure it’s not a false or phantom pregnancy.

Read on to discover what the signs of phantom dog pregnancy are, how a false pregnancy gets diagnosed and when medical treatment is necessary.

Phantom pregnancy in dogs refers to a condition where a female dog exhibits symptoms of pregnancy (like mothering behaviour after heat) but is not actually pregnant. This is also known as false pregnancy in dogs or pseudo-pregnancy and can affect any type of female dog, regardless of age or breed.

You can expect to see many of the same symptoms of an actual pregnancy to manifest in the case of a false pregnancy. Although the signs vary between individuals, these are the main physiological and behavioural changes to look out for:

Phantom pregnancies in dogs can happen after heat (i.e., the period where they’re most fertile.) However, it does not necessarily happen after every heat and can differ for each dog and their cycle.

The symptoms of a phantom pregnancy most commonly occur 6-8 weeks after your dog finishes her season, and should resolve within 2-3 weeks. Once your dog has had a false pregnancy after a season, it is very likely to recur at each subsequent season.

After a female dog has a season, she experiences a prolonged peak of the ‘pregnancy hormone’ progesterone lasting 8-9 weeks, whether she is pregnant or not. As levels of progesterone decline, levels of a second hormone, prolactin, increase, triggering the physical and psychological symptoms of pregnancy.

In some dogs this may be mild – not enough to notice – but in others the symptoms can be very convincing to both the dog and her owner.

The origins of phantom pregnancy in dogs are thought to be due to the pack behaviour of our domestic dog’s ancestors. All the females in the pack help to rear the family pups and feel motherly towards them, even when they are not their own offspring. This cooperative behaviour is driven by hormones.

High levels of the female sex hormone progesterone are produced during the two-month diestrus period that follows estrus. At the end of diestrus, a sexual dormancy period between cycles, progesterone concentrations in the blood fall rapidly while concentrations of prolactin, a hormone made by the pituitary gland that enables females to produce milk, begin to rise.

“The prolonged high progesterone levels stimulate mammary development and may loosen joints, giving some dogs an abdominal distension as their ribs ‘spring’ apart that mimics a pregnancy appearance,” says Dr. Root Kustritz. “The sudden fall in progesterone and rise in pro- lactin stimulate milk production and account for the whelp- ing behaviors that are observed in a false pregnancy.”

What is meant by false pregnancy? False pregnancy, phantom pregnancy, pseudo-pregnancy or pseudocyesis are all terms that refer to a display of maternal (mothering) behavior combined with the physical signs of pregnancy following estrus ("heat") in an unspayed female dog that is not actually pregnant.

• Lethargy.
• Depression and/or other behavioural changes.
• Loss of appetitive.
• Nesting – this can involve moving around and digging bedding.
• Nursing – your dog may become particularly attached to a toy.
• Secretion from mammary glands.
• Swollen belly.

False pregnancy, phantom pregnancy, pseudo-pregnancy or pseudocyesis are all terms that refer to a display of maternal (mothering) behavior combined with the physical signs of pregnancy following estrus ("heat") in an unspayed female dog that is not actually pregnant. A false pregnancy may occur in a dog, regardless of whether or not she was mated. The majority of intact female dogs will show some signs of false pregnancy after an estrus cycle.

Signs of false pregnancy usually begin four to nine weeks after the previous heat period and mimic the signs of true pregnancy. The more common signs of pseudo-pregnancy include mammary gland enlargement with or without the production of milk, lethargy, periodic vomiting, and fluid retention. Dogs with false pregnancy often have a decreased appetite but seldom appears to lose weight, likely due to the amount of excess fluid retained.

These signs can occur at any age and do not necessarily follow every estrus. The severity of the clinical signs varies between individuals and may vary from one cycle to the next in the same dog.

Behavioral changes of pseudo-pregnancy include nesting, mothering activity, restlessness, decreased interest in physical activity, and occasionally even aggression. Some affected dogs will show signs of a false labor and then protectively guard toys or other small objects.

After the female dog has an estrus cycle, her ovaries begin to produce hormones, regardless of whether she is pregnant or not. These hormones prepare the uterus to receive the fetuses and maintain pregnancy. If the dog is pregnant, the hormones will continue to be produced until shortly before the puppies are born. If she is not pregnant, the levels of the hormones begin to decline after 4-6 weeks.

In the early stages, the increased levels of circulating hormones cause changes that mimic pregnancy. As the hormone levels decline in the non-pregnant dog, they send signals to the body that stimulate false labor and mammary gland development. The reason that these hormonal changes occur in the non-pregnant dog remains a mystery.

Mild cases of false pregnancy do not require treatment since the symptoms will subside in approximately 14-21 days. If the dog appears physically ill or the behavioral changes are severe enough to cause concern, treatment is indicated.

Treatment is symptomatic and may include tranquilization to relieve anxiety and treatment with diuretics in order to reduce the milk production or relieve fluid retention. Do not massage or milk the teats during false pregnancy as this will only encourage more milk production. In rare cases, hormonal treatment may be required.

If your dog will not be used for breeding, ovariohysterectomy is recommended to prevent future episodes. Ideally, this surgical sterilization should be performed after all signs have resolved. If she is surgically sterilized while she is experiencing signs of pseudo-pregnancy, signs may continue for several weeks despite the fact she has been spayed.