Breeders with lots of experience in the whelping know how to prepare for whelping and manage the newborn puppies. 

But there are things you should know about whelping that you can't learn in the whelping box because they have to do with physiology and developmental biology - things that are happening in the puppies while they transition from one environment in the uterus to one in the real world where the conditions could not be more different. 

Newborn puppies are like premature infants. Not only are they helpless, but many of their organs are not fully developed. The kidney, brain, lungs, GI tract, and nervous system all undergo significant development in the weeks after birth, and during this time it is critical that there are no events that will affect development because any damage done to developing organs or DNA will affect the puppy for life. 
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It should not come as a surprise that there should be serious health consequences to the hypoxia experienced by many puppies during birth  The problems are familar and well-documented in humans and other animals, and dogs were even used as the experimental animal for some of these studies.

Likewise, breeders are very familiar with the rigors of whelping a litter of puppies, and many are experienced with reviving distressed puppies and, unfortunately, with the disappointment of stillborn pups.

What is astonishing is that this seems to be accepted as a matter of course, with nobody worrying about negative consequences. While breeders work diligently to reduce the risk of genetic disorders in their puppies, the potential damage caused to tissue and DNA by exposure to hypoxia during whelping is both greater and preventable.

It is understandable that lay breeders might not generally be aware of these problems. But studies of long-term effects on health of dogs exposed to hypoxia at birth are essentially non-existant, yet the health problems of dogs are a serious issue not just in the dog community but in the general public as well. Costs for care, shorter lifespans, and the need for long-time, chronic care for the dogs in our lives are unnecessary and preventable burdens. We need both education of breeders, activation of the veterinary and reserach community, and more acute attention paid to things that have long been accepted as either routine or of no consequence.

By doing some simple, basic things, we can have healthier, longer-lived dogs. We can start collecting data on health consequences of dystocia in dogs. We need to record the timing of whelping for each puppy. We need to starting whelping in darkness (not dim light but very, very dark). We need to become more attuned to things that would matter for a human infant but are normalized for puppies. 

Check out the blog posts below that I have written as my thoughts about whelping in dogs have developed. There will be more coming, as there is much more we need to learn about. Stay tuned.
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REFERENCES

Gill M.A. 2001. Perinatal and late neonatal mortality in the dog. (PhD Thesis) University of Sydney.

Hansbrough, F. et al. 1983. Pathogenesis of early necrotizing engerocolitis in the hypoxic neonatal dog. American Journal of Surgery 145: 169-175.

Hemker, S.L., 2016. The role of hypoxia during nephrogenesis. Pediatric Nephrology 31: 1571-1577.

Sha, W.R., et al. 2025. Necrotizing enterocolitis: what's new and what's next? International Journal of Molecular Sciences 2025, 26, 9660. 

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.

​Tonnessen, R., K. Sverdrup Borge, A. Nodtvedt, & A. Indrebo. Canine perinatal mortality: A cohort study of 224 breeds. Theriogenology 77" 1788-1801.

What causes fading puppy syndrome?

The short answer. The reason it's called a syndrome is that we don't really know.

Part of the problem of identifying it as a specific disorder is that it is ill defined. Basically, a puppy seems okay at birth but over the days after birth it might slowly decline or just suddenly die for no obvious reason. A puppy might show a bloated abdomen, poor body condition, dull or depressed activity, or fail to gain weight. It might be unable to suckle, cry constantly, have difficulty breathing, diarrhea, and as it continues to fail might lose muscle tone and be severely lethargic.  

Suspected or actual causes includes bacterial or viral infection, parasites, hypothermia, hyperthermia, poor sanitation, environmental toxins, inadequate colostrum, hemolytic anemia, genetics, congenital anomalies such as cleft palate or heart problems, poor maternal behavior, and improper gut microbiota (Singh et al. 2015).

Most published information about fading puppies remains descriptive and provides little more than suggestions for care. Feed by hand, give a dab of honey on the tongue, provide warmth, and if you end up at the vet, provide intravenous fluids or dextrose, maybe some antibiotics, and continue close observation. Often, despite the best efforts of vet and breeder, the puppy does not survive, sometimes after intense care and days of decine.

If there is one thing AI can do well, it's finding the connections among a bunch of things that don't at first seem to be related. 

I put the symptoms of fading puppy syndrome into Claude and asked what could explain these issues in a puppy.

My prompt:
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​"You are an expert veterinarian and pathologist. You examine a newborn puppy has or has had over the last couple of days, all or some of these symptoms: bloated abdomen, poor body condition, dull or depressed activity, fails to gain weight, suckles poorly, cries constantly, difficulty breathing, diarrhea, and lethargy.
Is there a single cause that could explain most of these symptoms?"

Claude's response:

ChapGPT has assumed that the puppy is two weeks old. I changed the prompt to indicate that the puppy was just a few days old after a slow whelping. The response:
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Claude has reduced a laundry list of probems and symptoms into a response to a physiological challenge that affects the entire puppy instead of separate organs or systems. 

Of course, this could be wrong. Perhaps adding a few more bits of information would change the diagnosis, as it did when I specified the pup had a slow birth and was just a couple of days old. But we could test this scenario with some data that could be easily collected by breeders: the duration of whelping, assessement of the condition of the puppy at birth (e.g., using the puppy APGAR system), the specifics of the condition of the puppy at birth, and daily followup. You don't know at birth which puppies might be faders, so you would need to collect information for each puppy from birth over the next few weeks at least. Records like this could allow us to connect symptoms to events, and if the theme turns out to be slow whelping and hypoxia, we will have identified a problem we can focus on solving.

It's surprising that we don't already have information like this. It would be easy to collect, and there are zillions of litters whelped daily that are tended to by breeders. A club could sponsor the systematic collection of data from a group of breeders and solve not only the fading puppy problem, but probably link a number of other disorders to the conditions a puppy experiences during whelping (Consequences to puppies of inadequate oxygen during birth).

This would be Citizen Science at its best, and it would help solve a huge problem in canine husbandry. I would love to see a group of breeders (or several) tackle this and collect the information we need to solve some health problems that we have struggled with for years. Contact me if you're interested!

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 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. 
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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.

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. 

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.

​What Birth Hypoxia Does to Puppies: The Hidden Damage
When a puppy is deprived of oxygen during birth (low oxygen is called hypoxia) because of a long delivery, strong uterine contractions squeezing the umbilical cord, a difficult presentation, or simply being born late in a large litter, the immediate danger is obvious. A puppy that is gasping, feels limp, has fluid noises in the lungs and airwayss, or cannot latch is a puppy in trouble, and every experienced breeder knows it.

What's less obvious, and arguably more important, is what happens to the puppies that aren't breathing at birth. Some of these come around with some stimulation, and others begin to breathe on their own only after some vigorous efforts by the breeder. Other pups might appear to be fine at birth - breathing, nursing, crying and getting around, then suddenly die a few days later. Oxygen deprivation during birth doesn't just threaten the puppies you can see struggling. It also quietly damages the ones that look fine.

The Puppy That Lives But Isn't Truly Well
The harder-to-recognize outcome is the puppy that grows up but carries the consequences of birth into adult life — in ways that neither the breeder nor the veterinarian will likely connect to what happened in the whelping box.

Brain problems
Oxygen deprivation kills brain cells through several pathways. It specifically targets the cells responsible for keeping the brain calm and regulated - the ones that put the brakes on excitement and stress. Puppies that lose these cells are more prone to anxiety, impulsive behavior, seizures, and difficulty learning. These problems tend to emerge gradually. They look like temperament. They look like bad luck. They almost never get traced back to a difficult birth.

Heart problems
Heart muscle cells are largely irreplaceable. When they die in a newborn due to oxygen deprivation, the heart compensates by enlarging the remaining cells, but that's adaptation, not repair. The heart that comes out the other side is structurally different from what it would have been without damage, and it remains more vulnerable to injury for the rest of the animal's life. A dog whose heart was quietly set on a different developmental path at birth may deteriorate faster with age, tolerate anesthesia poorly, or develop heart disease that looks genetic but was set in motion on the day it was born.

Blood vessel problems
Every artery and vein in the body is lined with a thin layer of cells that regulate blood pressure and control inflammation. Oxygen deprivation damages these cells in ways that persist into adulthood, resulting in chronically elevated blood pressure and a greater tendency toward inflammatory disease. This is an invisible change in a newborn puppy that may only show up years later as cardiovascular or inflammatory problems in the adult dog.

Lung problems
Neonatal oxygen deprivation can impair the normal development of the blood vessels in the lungs, with lasting effects on respiratory capacity and reserve.

A permanently altered stress response
Perhaps the most far-reaching consequence is what oxygen deprivation does to the system that governs how an animal responds to any kind of stress - physical, emotional, or environmental. That system gets calibrated in the neonatal period. When calibration is disrupted by an oxygen shortage at birth, the animal ends up permanently set to a higher state of alert: more reactive, less able to recover from stress, with a body that overresponds to challenges that a normally-born dog would handle without difficulty. This shows up as the dog that is "always a little off," that doesn't bounce back from illness the way its littermates do, that seems to find everything harder than it should.

One particularly striking research finding: the oxygen shortage at birth doesn't just cause damage. It also turns down the body's own ability to repair that damage. The same event that caused the problem also undermines the response to it, and that suppression gets locked in permanently.


What This Means in the Whelping Box
The puppy you saved with a rub and a prayer, the one born blue that pinked up after two minutes of stimulation, the one that was the last out after a long labor - that puppy may be carrying invisible damage throughout its body. The damage doesn't announce itself. It waits.

It may wait three years, until a dog that "shouldn't" have seizures has one. It may wait five years, until heart disease shows up in a line with no history of it. The sudden appearance of a cancerous lump and a life ended before middle age. The damage may never produce a dramatic event at  all - just a dog with chronic GI problems, or an uneven temperament, or that never quite reaches its potential, or that wears out sooner than expected, or that struggles with things its siblings handle easily.

One thing is increasingly clear: many of the health problems that appear in middle-aged or older dogs have their roots in the process of birth. Slow whelping that exposes a puppy to low oxygen levels before birth can produce damage that is immediate, but it can also seed the origins of health problems that might become chronic, or that are not even evident until years later.

What causes uterine inertia?
If uterine inertia is the reason for slow whelping, and the light conditions in the whelping room are affecting the hormones that cause strong uterine contractions, then we need to understand the effects of light on whelping.