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If you’re like me, you don’t make decisions related to your dog’s health based on just one source of information.

You prefer to hear “both sides of the story,” but when it comes to decided when, if ever, to spay your female dog, you may have noticed that there’s many, many, many sides to this story, and clear answer to your questions.

I teamed up with Delay Her Spay to find scientific studies that show the effects of spaying, both at an early age and after a heat cycle or two, to help you make an informed decision that makes sense for your dog.

This was an incredibly challenging post to write. There’s hundreds of research studies available, many with conflicting conclusions, and some factors have still not yet been fully investigated. I hope I can answer at least some of your questions so you can make a decision you feel good about.

How Does Spaying Affect Growth?

Spaying delays the closure of your dog’s growth plates, which can actually make her grow to be taller if she’s spayed before her first heat cycle. Prior to growth plate closure, though, your dog is vulnerable to bone and joint deformities, so spaying will keep her at risk for a longer time. Spayed or not, avoid strenuous activities with your puppy. Do not allow her to jump on and off furniture, and encourage low-impact exercise only.

Spayed females are 2-3 times more likely to develop cranial cruciate ligament tears or rupture (CCL).

Does Spaying Cause Incontinence?

Studies show that anywhere from 6% to 20% of spayed female dogs develop incontinence in months or years following the surgery. It’s actually been shown to be much less common in dogs that are spayed before their first heat.

After the dog is spayed, their body produces less estrogen. One purpose of estrogen is to support the urinary tract, and without it, your dog may find it more difficult to control her bladder.

Spay incontinence usually appears as dribbling while sleeping or during certain activities like hopping up stairs. It can be managed, even cured with several different treatments. In 60-65% of dogs with spay incontinence, estrogen treatments are all they need to restore control of their bladder. This tells us that estrogen is, among other things, very important to your dog’s urinary health.

Though it’s a common condition, particularly in large dogs, spay incontinence would only be a small factor in my decision whether to spay, and when. There’s no way to predict if spaying would have this effect on your dog – though some breeds are more prone to it than others.

Does Spaying Cause Weight Gain?

Spaying does increase your dog’s chances of gaining too much weight and becoming obese, regardless of her age when she is spayed. The good news is, this effect only lasts for two years after the surgery.

If you monitor your dog’s weight, increasing exercise and reducing her caloric intake if she seems to be gaining, she’s going to be fine. Weight gain should not be a factor in your decision to spay your dog.

Does Spaying Change Your Dog’s Behavior?

Data on whether or not spaying affects dog behavior has been tough to find. Surveys are tough to validate because though owners may report their dog’s undesirable behaviors, they might not understand the root causes.

Testosterone can drive increased aggression in male dogs, so it makes sense that neutering can decrease aggression in males. But aggression and reactivity may actually increase in spayed females, particularly those that began showing signs of aggression before the age of six months.

I wouldn’t jump to the conclusion that spaying your dog will necessarily make her aggressive or reactive. The procedure itself, the handling and overnight stay at the veterinarian’s office could be traumatizing and make her distrustful of humans; it’s unclear if any studies addressed this.

Does Spaying Prevent Cancer?

Spaying your dog before her first heat dramatically reduces her chances of ever developing mammary cancer. 

However, spaying increases your dog’s chance of developing other types of cancers, including canine lymphoma, hemangiosarcoma (four times more likely in spayed females) and mast cell tumors.

Approximately 50 percent of dogs over age 10 will be diagnosed with at least one type of cancer. Incidences have increased in the last decade, possibly due to an increased exposure to toxins, or the prevalence of spaying and neutering.

You can reduce the risk of some cancers and increase the risk of others no matter which decision you make. So, this data only makes the decision more difficult.

Does Spaying Eliminate Pyometra?

Pyometra, a potentially fatal infection of the uterus, is common in females older than 6 years. An intact female has a 15-24% chance of getting it in her lifetime.

If your dog does not have a uterus, she cannot get pyometra. The infection often occurs shortly after your dog’s heat, because fewer white blood cells are present in her uterus to help aid insemination.

This is a big reason to get your female spayed. The risk is not as prevalent when she is young, but as she gets older, you should seriously consider this as a factor in deciding to get her spayed at some point.

So… Should You Spay? And When?

In this one blog post, I’ve cited numerous studies, and a few articles that referenced hundreds more. Taking in all of this data, you can try to make the best decision for your pets. But there’s no right or wrong answer.

Consider which conditions are prevalent in your dog’s breed, and whether those are more common in spayed or unspayed dogs. Think about whether you’ll have to worry about the immediate risk of your dog possibly getting pregnant, or if you’ll find it easy to keep her away from intact males.

If you choose to keep your dog intact for her first heat, or for the rest of her life, use a dog “chastity belt” like Delay Her Spay to make mating impossible. Delay Her Spay can also be used as a sanitary pad to keep your furniture clean.

Lindsay Pevny
Lindsay Pevny lives to help pet parents make the very best choices for their pets by providing actionable, science-based training and care tips and insightful pet product reviews.

She also uses her pet copywriting business to make sure the best pet products and services get found online through catchy copy and fun, informative blog posts. She also provides product description writing services for ecommerce companies.

As a dog mom to Matilda and Cow, she spends most of her days taking long walks and practicing new tricks, and most nights trying to make the best of a very modest portion of her bed.

You'll also find her baking bread and making homemade pizza, laughing, painting and shopping.