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Wednesday, March 23, 2011

When To Spay Or Neuter

A common debate among veterinarians, shelters, and clients is when to have a dog or cat spayed or neutered.  The consensus and opinions have changed over time, and there can be some big disagreements depending on someone's experience and education.  A recent article in the journal Veterinary Medicine discussed the current views on the pros and cons of this kind of surgery on very young pets, and I thought it would be good to bring it up here.

First of all, we need to define "pediatric" spaying and neutering.  This normally means performing the surgery between 8 and 16 weeks of age.  Older vets would balk at this because the recommendation used to be to wait until six months old or after one heat cycle.  Current thinking has pretty much disproven the need to wait this long, so now most vets are spaying and neutering between four and six months old.  Most of the very young surgeries are done through shelters and rescue agencies, wanting the pet sterilized prior to being adopted out. 

Since there are many concerns about doing pediatric surgeries, let's briefly mention some of the myths (all taken from the above article) of the risks of doing these procedures.
1.  Obesity.  A long-term study at Cornell University showed that dogs who had early spays and neuters actually had a decrease in obesity risk.
2.  Stunted growth.  Removing the hormones early actually allows the growth areas of bones to stay open longer, so pediatric spays and neuters can grow taller than their late-sterilized counterparts.
3.  Hip dysplasia.  The jury is still out on this, but studies seem to be showing no increase or only a slight increase in risk.
4.  Feline urinary obstruction.  No increase risk has been found.  In fact, the diameter if the urethra is no different in cats neutered at 7 weeks or 7 months old.
5.  Urinary incontinence.  Again, the results are mixed.  One study showed an increased risk in females spayed before 12 weeks old, one showed no increased risk, and one showed an increased risk if spayed after the first heat cycle.

So overall, there appear to be no documentable long-term risks to surgical sterilizing at 2-4 months old.  What about surgical risk?  With current anesthetics and monitoring, the risks are not significantly different than waiting until later.  This was even true when I was in vet school in the late 90s, which is where I first saw some of this data.  As long as the vet is careful and monitors adequately, the surgery can be just as safe as in a six month old pet.

So with this information, why don't more people spay and neuter early?  In part I believe it's an ingrained tradition and habit in the veterinary profession.  We're just used to doing it at a certain age, and doing it younger makes us nervous because we don't really have personal experience with it.  I also think that it has to do with the timing of vaccines.  We finish the vaccines at around four months old, and it's easier to keep them on a regular schedule if we don't throw a surgery in prior to that.  It's simply convenient timing that once we finish the puppy/kitten boosters we next schedule their surgery.  But based on available data, there aren't many good reasons to have to wait that long.

Now does this mean that we as a profession should move to spays/neuters at three months old?  No, I don't think so.  There's really nothing wrong with doing it at the 4-6 month mark as most vets seem to do.  But it does mean that we shouldn't be afraid to do it younger, and shouldn't criticize those who do.  I'll continue to recommend the surgery at around four months old, but I have done it as early as 10 weeks (for reasons other than needing them sterilized) and had no issues at all.

Food for thought!


  1. Your reason number 2 is the reason why I'd wait until the dog is mature. The only other person who mentioned stunted growth was also someone in the vet industry, she argued that her dog was bigger than most of his breed not stunted, which proved the point I was trying to make re the growing.

    Why wouldn't growing taller than nature intended be as worrying as being stunted?

  2. To Linda Ward, this is exactly what I was surprised this article didn't cover.

    Growing taller than nature intended is extremely worrying in larger breeds who already have a significant risk of bone and joint issues. By pediatric neutering, the dog's bones grow taller with less density--a lighter bone on a taller body puts severe strain on the joints meaning an increase in hip or elbow displaysia, osteoarthritis, cruciate ligament disease, and more.

    Not only does this increase your chances of a very high vet bill down the road but also means a lot of pain for your dog which is the most important thing in the whole procedure.

    Early castration also increases their risk for prostatic neoplasia, transitional cell sarcoma, osteosarcoma, hemangiosarcoma, CCL injury, obesity, diabetes mellitus, and hypothyroidism.

  3. One of the problems that communities are grappling with today is the numerous animals that are left without shelter or a place to call home. Yes, there are many dogs that have loving and kind families that care for them. See more

  4. I don't know why there is such a dichotomy of preference of private vets vs shelters. I took in 2 cats from 2 different litters. I wanted them fixed and I thought 4months was a good age. I got them at 8 and 11wks respectively. However, I call around to vets and they all refuse to do it that "soon!" Say I must wait until 6mos. Excuse me?? The shelters do it at 2mos!! I try to double that and they insist I cant do that young. Meanwhile have a female 12wk old and a male 9wk now, unrelated, and I want to prevent not only babies, but teen behavior problems :-/ Am I being punished for not taking a shelter pet?


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