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Canine Maternal Hydrops in Dogs: A Little Known but Dangerous Pregnancy Complication


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

Not a lot is known about canine maternal hydrops (CMH). A rare condition in canines, it has been documented in few canines, including a Yorkshire Terrier, Golden Retriever, and Pug. The litter sizes of the pregnancies studied were recorded as normal to large. 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 this rare condition called canine maternal hydrops, and raise any concerns with a vet.

What is Known About Canine Maternal Hydrops?

Research is lacking on this condition; information comes primarily from a few studies and breeders who have pooled their knowledge. Here is what is known to date:

  • CMH is more common in first pregnancies

  • It's often 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

    • 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. Suggestions 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. 

Caring for a pregnant or breeding dog can be expensive. Most accident and illness policies don’t cover costs related to pregnancy. But some providers, like Trupanion, offer add-ons that reimburse vet care costs. Start comparing pet insurance plans today to find the right fit for your fur-baby.

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