Pregnancy loss in dogs - why does it happen?
As dog breeders, few things are more devastating than losing puppies during pregnancy. Whether it happens early through resorption or later as an abortion, pregnancy loss impacts both our emotional wellbeing and breeding programmes. A recent paper by Mantsiaris and Pipan gives a comprehensive overview of the reasons for pregnancy loss in dogs. In this article, we summarise some of their key points.
The Stages of Pregnancy Loss
Understanding when and how pregnancy loss occurs helps us better recognise and address potential problems:
1. Early Embryonic Death
- Occurs in the earliest stages when embryos are free-floating in the oviducts and uterus
- Often happens before day 19 of pregnancy
- Usually impossible to diagnose since it occurs before ultrasound can confirm pregnancy
- May result from altered uterine environment, inflammation, infection, or hormonal changes
2. Resorption (Days 19-35)
- The embryo is absorbed by the mother's body
- Can be detected via ultrasound
- Recent studies show surprisingly high rates:
* Some research found at least one resorption site in 30-48% of pregnancies
* Overall resorption rates range from 10.6% to 17.3% of all conceptuses
3. Abortion (After Day 35)
- Expulsion of dead or non-viable foetuses
- If a foetus dies but isn't expelled, it may:
* Develop emphysema and maceration
* Become mummified (if other normal foetuses are present)
* Cause toxemia or sepsis in the mother
Major Causes of Pregnancy Loss
The paper lists 7 categories of reasons for pregnancy failure:
Endocrine disorders;
Infectious causes:
Bacterial causes;
Protozoal causes;
Viral causes;
Uterine pathology;
Exogenous drugs;
Age;
Congenital defects and genetic disorders;
Other conditions.
Endocrine disorders
Endocrine disorders include Hypoleuteoidism, Gestational Diabetes and Hypothyroidism. Hypoluteoidism is associated with insufficient progesterone production by the corpora lutea and can cause pregnancy termination if levels drop too low. German Shepherds may be predisposed. Treatment involves progesterone supplementation but timing is crucial and this condition may be overdiagnosed - recent research shows successful pregnancies with lower progesterone levels than previously thought.
Gestational diabetes is rarely reported but affects neonatal survival and is not a cause of resorption or abortion. Common clinical signs include excessive thirst or urination,weight loss despite increased appetite, and lethargy. Medical management includes a low carbohydrate diet and insulin injections.
The evidence linking hypothyroidism to foetal loss is mixed, so other causes are more likely to be considered first.
Infectious Diseases
Bacterial Infections:
- Brucella canis
* Causes abortions between days 45-55 of gestation
* Can also affect early pregnancy (days 10-35)
* Transmitted through contaminated materials or breeding
* Required testing and isolation of infected animals
* No vaccine available
- Streptococci
* Can cause abortions around days 30-40
* May be associated with neonatal death
* Often found in normal vaginal flora but can become problematic
- Other bacterial infections include E. coli, Campylobacter jejuni, Salmonella spp, Listeria, and Leptospira
Protozoal causes:
Toxoplasma gondii
Neospora canimum
Leishmaniasis
Viral Infections:
- Canine Herpesvirus
* Most dangerous for newborn puppies
* Role in pregnancy loss may be overestimated
* Vaccination available for pregnant bitches
* Keep puppies warm to prevent virus replication
- Canine Parvovirus Type 1
* Different from the more common CPV-2
* Can cause embryonic resorption and abortion
* May lead to birth defects
* Vaccination is recommended for breeding animals
Other potential viral causes are Distemper and Adenovirus.
Uterine Pathology
Several conditions can affect the uterus:
- Cystic Endometrial Hyperplasia (CEH)
* Characterized by enlarged, cystic endometrial glands
* Makes proper placentation impossible
* Can affect young bitches, not just older ones
* May exist without obvious clinical signs
- Subclinical Endometritis
* Often undetected in routine examinations
* Research shows it's present in many cases of unexplained infertility
* Diagnosis requires uterine biopsy or specialized sampling techniques
Exogenous Drugs
Drugs used to treat a health condition during pregnancy or the inadvertent ingestion of drugs, poisons or hormones can be harmful to pregnant bitches and their embryos and foetuses.
Age-Related Factors
Recent research highlights the importance of age. Both very young and older gametes are associated with reduced fertility in both males and females. Bitches over six years show a significant decline in conception rates. Nulliparous (1st litter) bitches may have lower conception rates than multiparous ones. It is also known that breed differences play a role in both reproductive performance and litter size.
Congenital defects
Early foetal loss can also be associated with genetic disorders that are incompatible with survival. Osteogenesis imperfecta is an example of a condition found in Dachshunds where affected puppies rarely survive or have to be euthanised soon after birth. Genetic abnormalities have been reported to be responsible for around 15% of infertility cases or pregnancy loss in dogs.
Other conditions
These include uterine torsion and maternal trauma during pregnancy.
Actions for breeders
If you experience repeated pregnancy losses, don't assume it's just bad luck. Work with your vet to investigate the cause and develop appropriate solutions. Many causes of pregnancy loss are preventable or treatable when caught early.
Research continues to advance our understanding of canine reproduction. New diagnostic techniques and treatment options are being developed, offering hope for better outcomes. As breeders, staying informed about these advances and maintaining close relationships with reproductive specialists helps us provide the best care for our breeding dogs.
Prevention and management strategies include:
Health screening of bitches and stud dogs
Ensuring puppies receive the recommended vaccinations
Pregnancy monitoring for abnormal behaviour
Environmental management to avoid risks (diet, stress, drugs, poisons)
Remember: Each pregnancy loss provides an opportunity to learn and improve our breeding programmes. Keep detailed records, work closely with your vet, and seek specialised help when needed.
Read our Breeding Advice page for more information.
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