Pregnancy in the Dog: A Little Known but Dangerous Complication

Are you thinking of breeding from your female dog?

For the female dog, pregnancy and rearing pups is hard work and sometimes distressing. And that's a straightforward pregnancy and whelping. Things can and do go wrong. One complication, canine maternal hydrops, is dangerous for the mother and can lead to both maternal and puppy deaths.

What's even more scary is that not a lot is known about maternal canine hydrops (CMH). Golden retrievers seem most affected, along with mothers of large litters. The problem is the result of unusually large fluid sacs around each puppy in the womb. The huge volumes of fluid within the womb compress vital arteries and veins in the mother's belly, putting a strain on her heart. In the worst cases, the mother dies because of heart failure.

If your female dog is pregnant, be vigilant for signs of canine maternal hydrops and raise any concerns with a vet.

What is Known About Canine Maternal Hydrops?

Research is lacking into this condition; information comes primarily from breeders who have pooled their knowledge. Here's what's known to date:

  • CMH is more common in first pregnancies

  • Golden retrievers seem most at risk

  • It's linked to large litter size (10 puppies or more)

  • Signs include:

    • A belly that is unexpectedly swollen for her stage of pregnancy

    • A rock hard belly

    • Swelling of the limbs and vulva (sometimes grapefruit sized)

    • Difficulty seeing the fetal skeletons on late gestation x-rays (due to the presence of large volumes of fluid)

    • Leakage of clear fluid from the vulva in the last stages of pregnancy

    • A depressed, dull dog with little interest in food

What Causes Canine Maternal Hydrops?

The truth is, no-one knows. Suggests and theories include:

  • A mismatch of blood type between the mother and the puppies in the womb

  • Hereditary causes. Although unproven, there is some thought this accounts for a similar condition in horses and cattle

  • An infectious cause. This theory is again unproven

  • Environmental causes. This could include exposure to chemicals, foods, supplements, or other factors 'outside' the dog.

How is Canine Maternal Hydrops Treated?

This condition can endanger the mother's life. Rather than experience the strain of labor, she should have a planned C-section. But the dangers don't end there. She loses large volumes of fluid from the womb during the surgery, which can send her into shock. Therefore it's vital she has aggressive intravenous fluids during the op.

There also seems to be an increased chance of the puppies dying after delivery. Anecdotally, antibiotics post whelping may help with this.

In short, CMH is a dangerous condition about which not a lot is known. If you are planning on breeding your dog, be vigilant during her pregnancy for signs of an unusually large, hard belly. In addition, it's a good idea to have the vet estimate how many puppies are present, so you can decide if a planned C-section is advisable or not.


Here's to the patter of tiny paws, and a happy, healthy mother!

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