By Carol Beuchat PhD
Uterine inertia that results in slow whelping is well-documented in dogs. Multiple studies have reported on the duration of whelping, the timing of births, mortality and morbidity of puppies, and potential causes across many breeds (Gill 2001; Tonnessen et al 2012; Cornelius et al. 2019). (Why do newborn puppies die?; We can prevent neonatal puppy mortality)
| The frequency of stillborn and distressed puppies because of uterine inertia is highly variable. Among all breeds in a sample of 2,660 litters, 4.3% of puppies were stillborn and 3.7% died shortly after birth, for a total loss of 8.0% (Tonnessen et al 2012). The incidence of both stillbirths and distressed neonates varies widely among and within breeds, and in some cases entire litters can be lost. (See tables at the end.) These and other studies show that uterine inertia can result in birth intervals between puppies of several to many hours, and a total duration of labor that can exceed 36 hours or more. |  |
Slower whelping results in increased risk of stillborn puppies. An increase in "inter-pup interval" of only 10 minutes increases the percentage of stillborn puppies by about 15% (y = 3.77 + 0.147x; r2 = 0.95; n = 19,577).
In a study of nearly 20,000 puppies whelped from 2,489 litters, necropsies of stillborn puppies shows that the cause of death is usually intra-uterine anoxia; i.e. inadequate oxygen before birth (Gill 2001). The stillborn puppies lack enough oxygen in the placenta and their blood supply to last until the pup is born into ambient air. Many puppies that are distressed at birth, and even some that appear to be perfectly normal, show signs of intra-uterine hypoxia (inadequate oxygen) (Gill 2001).
The consequences of inadequate oxygen during birth are well known in both full-term and premature infants. The primary health issue caused by perinatal hypoxia is hypoxic-ischemic encephalopathy (HIE), which can result in permanent brain damage, as well as developmental delays and disabilities like cerebral palsy. The severity of damage depends on the duration of oxygen deprivation. There is also a variety of other neurological, respiratory, and cardiac effects.
Fetal asphyxia in human and non‐human animals, organ injury and physiological imbalances in response response to hypoxia–ischemia. Image (A) summarizes the neuronal damage at a biochemical and pathological level. Image (B) shows damage in other vital organs. In image (C), the physiological imbalances are appreciated due to the drastic reduction of oxygen to the fetus, and promote the expulsion of meconium. In letter letter (D) some adverse adverse effects if the newborn survives.
In contrast to the situation for humans and some domestic animals, there have been essentially no studies of effects of perinatal hypoxia dogs beyond documenting cause of death (Gill 2001). Because of similarities in physiology between humans and domestic animals, however, it is certain that periods of inadequated oxygen during birth should have similarly significant effects on dogs.
The two tables (below) indicate for humans, other mammals, and dogs the documented short-term and long-term effects of hypoxia during birth. You can see that the information for dogs is sparse, but you will also recognize a number of disorders on the long-term list that are familar problems in dogs, inculding epilepsy, renal dysplasia, anxiety disorders, renal dysplasia, gut dysbiosis, cancer.
Because of what we know about the physiology of hypoxia in mammals, we can be certain that hypoxia during birth in puppies must have significant consequences for health and welfare. Most notable about the disorders on these lists is the fact that in dogs, many are thought to be genetic and have received much attention from geneticists searching without success for causal alleles. Most of the genetic studies have been initiated without first determining the heritability of the disorder, which would have indicated the fraction of variation in the trait that can be accounted for by variation in genetics versus environment. This statistic would indicate when there is a significant environmental effect that should be examined, and that it should no be assumed that the cause is genetic. Indeed, many of the issues we should expect to see in dogs because they occur in other mammals are high on the list of the most problematic disorders faced by breeders. The assumption that genes must be the cause of most health problems has misdirected decades of research and selective breeding, when the underlying problem could well be something non-genetic like perinatal hypoxia. (What is “heritability” and why do you need to know?)
Many health problems that occur later in life could be the result of "fetal programming", where events at the time of birth result in problems that don't beome apparent until later in life. For these, making a connection between disorder and causal events at birth is difficult if you aren't familiar with the kinds of things that occur in other mammals. The tables above list general types of disorders, but much more detailed breakdowns of specific health problems would be useful to highlight issues that might be seen in dogs.
Many health problems that occur later in life could be the result of "fetal programming", where events at the time of birth result in problems that don't beome apparent until later in life. For these, making a connection between disorder and causal events at birth is difficult if you aren't familiar with the kinds of things that occur in other mammals. The tables above list general types of disorders, but much more detailed breakdowns of specific health problems would be useful to highlight issues that might be seen in dogs.
The lack of systematic efforts to identify the health consequences of the well documented problem of utereine inertia in dogs is surprising, and filling this gap should be a focus of veterinary research. It should also be stressed to breeders that trying to manage a health problem with selective breeding will not be successful if the cause is not primarily genetic. A first step in addressing the cause of a health problem should be calculating the heritability, which will identify problems with a substantial non-genetic basis.
An obvious problem to tackle is identifying the cause of uterine inertia. Among the causes suggested are litter size, age and parity of the dam, hormone problems, exhaustion, low birth weight, among others. But singly or collectively, these are not strongly predictive, and none provide a clear mechanistic reason. I have suggested that exposure of the dam to light during whelping can provide such an explanation, and offer a way to prevent dystocia by providing appropriate conditions for whelping in darkness. We have found that whelping is faster and goes smoothly when done in a dark room, with no stillborn or distressed puppies. I am continuing to explore the role of light in slow whelping, working with beeders in both a topical Facebook group and a new course that starts in April 2026.
For breeds struggling with health problems that might be a consequence of perinatal hypoxia, it would be worth whelping litters with controlled lighting conditions and collecting data for short and long term consequences for health. For at least some issues (e.g., renal dysplasia) that often appear early in life, useful data might be available in a year or two. But we know that the effects of inadequate oxygen in infants are profound, and an effort to prevent hypoxia in puppies should have a significant positive effect on the health and welfare of dogs.
For breeds struggling with health problems that might be a consequence of perinatal hypoxia, it would be worth whelping litters with controlled lighting conditions and collecting data for short and long term consequences for health. For at least some issues (e.g., renal dysplasia) that often appear early in life, useful data might be available in a year or two. But we know that the effects of inadequate oxygen in infants are profound, and an effort to prevent hypoxia in puppies should have a significant positive effect on the health and welfare of dogs.
To learn more about the causes and consequences of uterine inertia in dogs, visit our Facebook group -
https://www.facebook.com/groups/uterineinertiaindogs
https://www.facebook.com/groups/uterineinertiaindogs
References
Cornelius, A.J., R. Moxon, J. Russenberger, B. Havlena, & S.H. Cheong. 2019. Identifying risk factors for canine dystocia and stillbirths. Theriogenology 128: 201-206.
Gill M.A. 2001. Perinatal and late neonatal mortality in the dog. (PhD Thesis) University of Sydney.
Hutter, D., J. Kingdom, & E. Jaeggi. 2010. Causes and Mechanisms of Intrauterine Hypoxia and Its Impact on the Fetal Cardiovascular System: A Review. international Journal of Pediatrics. 2010 (doi:10.1155/2010/401323)
Mota-Rojas, D., D. Villanueva-Garcia, A.. Solimano, R. Muns, D. Ibarra-Rios, & A. Mota-Reyes. 2022. Pathyphysiology of perinatal asphyxia in humans and animal models. Biomedicines 10 (doi:10.3390/biomedicines10020347).
Tonnessen, R., K. Sverdrup Borge, A. Nodtvedt, & A. Indrebo. Canine perinatal mortality: A cohort study of 224 breeds. Theriogenology 77" 1788-1801.
Cornelius, A.J., R. Moxon, J. Russenberger, B. Havlena, & S.H. Cheong. 2019. Identifying risk factors for canine dystocia and stillbirths. Theriogenology 128: 201-206.
Gill M.A. 2001. Perinatal and late neonatal mortality in the dog. (PhD Thesis) University of Sydney.
Hutter, D., J. Kingdom, & E. Jaeggi. 2010. Causes and Mechanisms of Intrauterine Hypoxia and Its Impact on the Fetal Cardiovascular System: A Review. international Journal of Pediatrics. 2010 (doi:10.1155/2010/401323)
Mota-Rojas, D., D. Villanueva-Garcia, A.. Solimano, R. Muns, D. Ibarra-Rios, & A. Mota-Reyes. 2022. Pathyphysiology of perinatal asphyxia in humans and animal models. Biomedicines 10 (doi:10.3390/biomedicines10020347).
Tonnessen, R., K. Sverdrup Borge, A. Nodtvedt, & A. Indrebo. Canine perinatal mortality: A cohort study of 224 breeds. Theriogenology 77" 1788-1801.
Tables below are all from Tonnessen et al. (2012).
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Visit our Facebook Groups
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...the latest canine news and research
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...the science of animal breeding
