False pregnancy, which is also called pseudocyesis, is a condition that causes a female dog to develop symptoms similar to a dog that is about to have or just had puppies.
Affected dogs may develop enlarged mammary glands that may even start producing milk! They frequently start to collect and mother toys and occasionally will gain weight. Sometimes they will vomit or stop eating as if in preparation to deliver babies.
This can definitely cause confusion for both dog and owner.
If an intact (non-spayed) female dog has mated or has possibly mated within the last 2 months then routine temperature checks are often employed to help determine exactly when the dog will deliver her babies.
This monitoring typically starts at day 60 from the presumed date of mating. Temperatures are checked at least twice daily and recorded. Within 8 to 24 hours of expected delivery, a mother’s temperature will drop a few degrees from 100-102.5 generally to 99 degrees or less. This is due to a sharp decline in progesterone levels just prior to the onset of delivery (whelping). A rise in prolactin levels follows.
A drop in temperature can happen in canine pseudopregnancy just as well as pregnancy. A sudden decrease in progesterone triggers the decrease in temperature. A drop in progesterone happens after ovulation and can trigger false pregnancy. Thus, evidence of a drop in temperature cannot reliably determine if a dog is pregnant.
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When pseudopregnancy develops and which dogs are affected
Pseudopregnancy develops about 45-60 days after estrus (a dog’s heat cycle). A true pregnancy takes on average 63 to 65 days after mating during estrus. The timing of these two phenomena are very similar.
As the progesterone declines following ovulation in a non pregnant dog, prolactin will sometimes start to rise. When prolactin rises, it triggers a host of mothering behaviors like nesting, mothering of toys, increased aggression, mammary gland enlargement and milk production.
Domestic and wild dogs have developed the ability to form a pseudopregnant state presumably to aid in the nursing of litters of babies in the wild.
False pregnancy has been determined to be highest in certain breeds such as Afghan Hounds, Beagles, Boxers and Dachshunds. The incidence of pseudopregnancy in these breeds has been recorded to be as high at 50-75%! Although the pseudopregnant state has evolved as a normal process, there have been studies that suggest >3 episodes of pseudopregnancy in a dog may increase their risk for the development of mammary cancers.
Spaying during diestrus can trigger pseudopregnancy
In the United States and other countries which advocate for spaying and neutering companion animals, phantom pregnancy is much less common. When it does happen it may be seen as a result of spaying during diestrus. Diestrus is the phase right after estrus and lasts about 2 months. At this time, estrogen levels have dropped and progesterone levels peak.
Preventing pseudopregnancy in dogs
The best prevention for pseudopregnancy is to spay a dog before the very first heat cycle. Spaying before the first heat is recommended by most veterinarians in the US. This recommendation is based on a statistically significant decrease in malignant mammary cancers in dogs spayed before the first heat cycle.
Following diestrus, is anestrus, which lasts about 4 months. A timeline to consider following is spaying an adult female no sooner than 3-4 months from her estrus cycle to avoid diestrus. The phase of the heat cycle is always best determined by evaluating a vaginal swab to examine the predominant cell type. Diestrus can be distinguished by the predominant vaginal cells from a swab.
How to diagnose pseudopregnancy
Hormonal assays are not useful to diagnose pseudopregnancy from true pregnancy. Obviously if a dog was recently spayed, these symptoms can more easily be identified as a false pregnancy. Because pseudopregnancy develops 45-60 days from estrus, imaging studies of the abdomen should be able to identify the presence or absence of fetal structures.
How to diagnose pregnancy
The most common methods to diagnose pregnancy are based on imaging studies with either an ultrasound exam or an x-ray study to identify fetal skeletons. An ultrasound study can identify uterine vesicles by day 21. By day 28 fetal heartbeats should be recognizable. By day 45 fetal skeletons can be identified with x-ray studies. X-ray studies are the preferred method to determine fetal counts as it is difficult to accurately predict litter size based on ultrasound evaluation alone.
A hormone assay for the hormone relaxin produced by the placenta can be identified with a blood test by day 21. Testing by day 28 or later is recommended for improved accuracy. There are kits marketed online that can be purchased to test for the hormone relaxin. This test is available on Amazon.
The tests do require that a blood sample is collected and spun in a centrifuge to collect serum. A veterinary office may charge a small fee for the blood collection to be performed and the sample spun in a centrifuge.
Symptoms of phantom pregnancy in dogs
The two most commonly reported physical symptoms in dogs are mammary gland enlargement and milk production.
The two most common behavioral symptoms are collecting objects to mother and nesting behavior. Aggression is a much less commonly reported behavioral symptom.
Do not confuse pregnancy or pseudopregnancy with pyometra
A symptom that is not common in pregnancy or false pregnancy is discharge from vulva. During whelping or right before whelping, discharge from the vulva can be normal. However, if there is yellow to red malodorous discharge, extreme lethargy, increased thirst and urination and continued signs of inappetence and vomiting this is concerning for a possible uterine infection. If an intact female dog shows these signs, it is very important to have her evaluated by a veterinarian for the presence of a life-threatening condition called pyometra. An “open” pyometra will present with discharge from the vulva as pus leaks out.
However, some dogs have a swollen abdomen, and signs of feeling unwell with increased thirst and urination without any evidence of fluid leaking from their vulva. This is called a “closed” pyometra and can be even more dangerous. These dogs are at increased risk of having their uterus perforate and leak infection into the abdomen, causing sepsis.
If your dog is not feeling well it’s always best to consult your veterinarian.
Treatment of false pregnancy
Pseudopregnancy does not always require treatment. It can self- resolve within 1-3 weeks. However, treatment is recommended if symptoms are severe or last longer than 4 weeks. Some clinicians choose to try behavior modification first by discouraging nesting and mothering behavior and advising owners to not touch the abdomen/mammary glands. An Elizabethan collar or surgical suit like a suitical recovery suit can also be placed to prevent a dog from self- stimulating the mammary glands which can perpetuate the condition.
A drug like cabergoline should be used with a covering like a Suitical recovery suit to cover the mammary glands
There are several drugs that can be used to treat pseudopregnancy. However, the drug of choice is called Cabergoline. It has a long duration of action with very few side effects. Cabergoline is a prolactin inhibitor that suppresses rleast from the pituitary gland. If using a drug like cabergoline, it is important to cover the glands to prevent self-stimulation. If self stimulation occurs, it will counteract the effect to the cabergoline and likely cause treatment failure. Surgical suits like the suitical recovery suit can be very effective for this purpose.
Capergoline is typically prescribed for 5-6 days but sometimes requires close to 2 weeks of treatment. About 75% of studied dogs had their pseudopregnancy resolve after 5 days of treatment.
Delay spaying a dog with false pregnancy
Dogs should ideally not be spayed while showing signs of pseudopregnancy. This is because spaying can worsen and lengthen symptoms of pseudopregnancy. Timing of spaying following pseudopregnancy should be no sooner than 7 days from resolution of symptoms. After using a course of cabergoline, spaying should be planned no sooner than a week after completing a 5 day course.
Summary
False pregnancy is relatively common to see in intact female dogs. It developed as a way to protect litters of babies in the wild, by providing more than one female capable of nursing. Most cases of false pregnancy will resolve on it’s own in 1-3 weeks. Most dogs who are about to give birth will have a temperature of 98-99 degrees. This is not a useful screening test to discern pregnancy from pseuduopregnancy however. The drop in progesterone that triggers false pregnancy also causes a decrease in temperature.