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Puppy Absorption in Dogs: Definition, Causes & What to Know

japanese chin puppy lying on the rock

Puppy absorption in dogs is a bit of an under-studied topic. Often, the pregnancy cannot even be confirmed before some or all of the fetuses are reabsorbed. Most of the time, the dog owner may not even know that their dog was pregnant at all!

With that said, breeders often contend with this mysterious occurrence regularly. While obviously sick dogs do reabsorb their pregnancies, completely healthy dogs do as well.

Sometimes, the cause is quite obvious. Other times? Not so much.

There are some steps that breeders and pet owners can take to avoid puppy absorption. However, there is not a fool-proof way to completely prevent it.

If you’re lost on everything we’ve mentioned so far, read on. We’ll discuss everything you need to know, including potential causes and complications.


What Is Canine Fetal Resorption?

Just as the name suggests, puppy absorption – also called canine fetal resorption – happens when the mother dog reabsorbs fertilized eggs into her body. The puppy has already stopped developing at this point and is considered deceased.

The puppy’s body begins to decompose within the womb. The enzymes in the fetus completely separate and are then reabsorbed into the mother’s bloodstream.

This process is slightly different from embryo loss, which occurs very early in pregnancy. Puppy absorption can occur any time before 44 days. After that, the puppy’s bones are too hard to be broken down and cannot be absorbed.

Canine fetal resorption often occurs fairly early in pregnancy. In many cases, the cause is completely out of anyone’s hands. The fetuses affected often have some sort of genetic abnormality that causes them to stop developing.

Usually, only one or two puppies in a litter are absorbed. Therefore, the dog usually stays pregnant. The fetus literally disappears from the uterus and is reabsorbed into the dog’s body. It is not the same as a miscarriage, where the fetus is expelled.

While this process may seem a bit unsettling, it is a very common process. Reabsorbing the fetus allows the mother and other puppies to continue with a healthy pregnancy.

In fact, up to 44% of dogs may experience fetal resorption.

pregnant Dogue de Bordeaux
Image Credit: Jan Dix, Shutterstock

What Causes Fetal Resorption in Dogs

There are likely countless reasons for puppy reabsorption. Because it happens so early in pregnancy, owners often don’t know that it happened. There are usually no outwards signs, and the female typically continues on with a healthy pregnancy.

Usually, causes fall into two main categories: infectious agents and non-infectious agents.

  • Virus Infection – A few common canine viruses can affect the health of developing puppies. For instance, canine herpesvirus 1A can cause infertility and pregnancy loss. Females are often asymptomatic, so it isn’t odd for owners to be completely unaware that their dogs are infected. Canine distemper virus can also cause spontaneous abortion and reabsorption – even if the fetuses themselves are infected. The reabsorption is thought to be caused by the stress of the illness in this case. Canine parvovirus is also linked to very early puppy reabsorptions.
  • Hypothyroidism – This condition occurs when the female does not make enough progesterone for one reason or another. This hormone is required for the dame’s body to know that she is pregnant. Without it, it is difficult to maintain pregnancy. Therefore, embryos may not stick to the inside of the uterus properly, leading to their inability to develop and reabsorption. Often, this condition causes complete pregnancy loss – not just the reabsorption of a fetus or two.
  • Uterine Deformities – If a female’s uterus is not properly formed, some fetuses may have a hard time developing correctly. Sometimes, this deformity leads to serious infertility problems. In minor cases, it may simply make it difficult for one or two fetuses to develop properly, leading to reabsorption.
  • Diseases – Seemingly unrelated infections and health problems can cause puppy reabsorption. For instance, diabetes can cause fetal reabsorption if it is not controlled properly. Hypothyroidism directly affects a dog’s hormones and can also lead to pregnancy loss. Often, dogs have a seriously hard time getting pregnant in the first place with these conditions. Therefore, this is a less likely cause.
  • Fetal Defects – As we previously stated, fetal resorption is often due to a problem with the fetus itself – not the mother. Sometimes, the fetus is not genetically sound and could never develop into a healthy puppy. Often, these fetuses stop developing early on and are then reabsorbed.
  • Stress – Though there is no evidence for it, it is suggested that maternal stress can also cause pregnancy loss. We know that stress caused by unrelated illnesses can cause reabsorption, but it is unclear if stress caused by environmental factors has the same effect.
  • Poor Nutrition – Proper nutrition is required for fetuses to develop properly. If the mother does not consume everything she needs, some of the fetuses may not get the proper nutrients or calories. This deficiency can cause them to stop developing or develop incorrectly. In some cases, this can lead to fetal resorption.
Pregnant pug
Image Credit: Ezzolo, Shutterstock


When It Isn’t Really Fetal Resorption

There are several occurrences that are often mistaken as fetal resorption – but aren’t actually linked.

For instance, false pregnancies are sometimes misdiagnosed as puppy reabsorptions. The dog will often experience pregnancy symptoms, including milk production and weight gain. However, there are no actual fetuses present. At some point, the female will simply stop having symptoms.

When this occurs, many dog owners assume that the female has reabsorbed the fetuses, though this isn’t the case.

It is also possible for early ultrasounds to be wrong. They could indicate a fetus where there isn’t one. When the female later gives birth to a smaller number of puppies, it is assumed that she reabsorbed one or two.

As you might imagine, it can be nearly impossible to set these things apart. How do you know whether it was a false ultrasound reading or puppy reabsorption? You don’t. It’s impossible to tell after the fact.

False pregnancies and puppy reabsorptions are also nearly impossible to tell apart after they have occurred. While the dog is still pregnant, you can use an ultrasound to determine whether the pregnancy is real or false.

However, after the pregnancy symptoms have dissipated, there is no way to know if the pregnancy was false or the fetus reabsorbed.

pregnant jack russell in bed
Image Credit: Gladskikh Tatiana, Shutterstock


Final Thoughts

Fetal resorption is often completely unnoticed by breeders and dog owners alike. Unless the fetus is reabsorbed somewhat late and the dog undergoes an early ultrasound, this process is nearly undetectable.

There are many different causes – most of which are completely out of your hands. Many puppies are reabsorbed because they are not genetically sound. They may not develop whole organ systems for this reason.

Eventually, they will stop developing, and the body will reabsorb them. In many cases, this happens very early, before you even know the dog is pregnant.

Other times, illnesses and infections can cause pregnancy loss. Many underlying conditions are associated with decreased puppy survival rates. Viruses can directly affect fetuses, and infections can compromise the mother’s ability to carry a healthy pregnancy.

No matter the cause, puppy reabsorption is often nothing to be worried about. Unless it was caused by a chronic, underlying condition, it is often just part of the breeding process.

Featured Image Credit: Ann Marie Kurtz, Shutterstock

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