What is the best age to spay a female dog? A simple enough question, but the answer is complicated.

The Short Answer

The short answer about when best to spay a female dog is to know the risk factors for your particular type of dog and to make a decision for them as an individual.

Key to deciding are:

  • The dog’s anticipated size as an adult
  • The dog’s breed

This is because vets now recognize some dogs are at greater risk of certain long term complications than others, including:

  • The risk of mammary cancer (breast cancer)
  • The risk of other cancers such as bone cancer (osteosarcoma or haemangiosarcoma)
  • The risk of urinary incontinence

These risks go up or down as outlined later in the article, hence the need to think of each pet as an individual.

Old Approach

The old approach was blanket advice:

  • Spay a female dog before the first season that is at around 5 – 7 months of age.

This advice was based on a scientific paper (Schneider et al) showing a reduced risk of developing serious mammary cancer, when dogs were spayed early.

The stats look convincing.

  • Neuter before the first season and the risk of mammary cancer in later life is 0.5% (one-in-200 hundred dogs.)
  • Neuter after the first season and the risk is 2 – 8 % (between one-in-20 and one-in-12 dogs)
  • Neuter after the second season and the risk is 26% (around one-in-four)

But this advice has been called into question and is now widely regarded as too simplistic. With dogs ranging in size from the 2kg Chihuahua to the 100kg Mastiff, it simply isn’t possible to apply the same rule to all.

New Approach

This is to balance the known risks for each individual dog. Boiling it down to the simplest take-home message:

  • Spaying between the first and second season has the best compromise between health benefits and drawbacks

However, even this approach is too simple because of certain breed-related complications. Studies now seems that breeds such as Rottweilers and German Shepherds are better neutered after two seasons. To go ahead sooner appears to carry a small increased risk (although still tiny, set against the breed pre-disposition to certain conditions) of osteosarcoma and haemangiosarcoma.

 Hence, why you should discuss your dog’s needs with a well-informed vet.

Balancing the Benefits and Drawbacks

Why neuter a female dog at all?

OK, let’s set aside the moral argument about pregnancy and controlling the dog population. Instead, I want to focus on the medical benefits/ drawbacks to that female dog of neutering.

The Benefits

  • Entire, un-spayed females are 3 – 7% MORE likely to develop mammary cancer than spayed females
  • Spaying eliminates the possibility of developing pyometra (a potentially life-threatening womb infection). This is thought to occur in 15% of female dogs by the age of four-years old
  • Spaying prevents pregnancy and the risks associated with giving birth
  • Diabetic female dogs are better controlled on insulin than entire females

The Drawbacks

  • A spayed female dog is at greater risk of developing urinary incontinence that an entire female, especially in large or giant breeds
  • Early work suggest a small increase in the risk of developing allergic skin disease (atopy)
  • Some breeds seem prone to an increased risk of cruciate rupture (in particular Golden Retrievers)
  • Neutered females need to watch their waistlines more carefully

The Breeds with the Biggest Question Marks

As more data becomes available for analysis, so the picture about when to spay a female dog changes.

Currently, the biggest buzz is around breed-related risks. Those breeds with the biggest question mark over the timing include:

  • Rottweiler
  • Golden Retriever
  • Labrador
  • Hungarian Vizla
  • German Shepherd dog

It seems sensible that these breeds do best when they have AT LEAST ONE SEASON. But the jury is still out as to whether two seasons are optimal or not.

The argument is along the lines of balancing a known risk of delay (marginal increase in the risk of mammary cancer) with an emerging drawback of an increase in the risk of other serious cancers and a recognized increased risk of urinary incontinence.

Keeping Things in Proportion

When all’s said and done, it’s important to keep things in proportion.

Take a drawback such as urinary incontinence. The biggest risk of this condition developing is if surgery goes ahead very young (before eight weeks of age.)  Older than this and the increased incidence is controversial with different studies giving different figures, with the most recent in December 2019 being just 0.68%.

Also, taking the example of urinary incontinence there are LOTS of other risk factors such as:

  • Body weight: Bigger dogs (that aren’t overweight) are over twice as likely to develop incontinence as those weighing less than 20kg
  • Body condition: Overweight dogs are at increased risk compared to their svelte cousins.
  • Age: Even entire female can develop incontinence, with the risk going up with greater age.

Let’s be clear about the message. Neutering a female dog is still a good idea, however there no such thing as a one-size-fits-all to the best age to spay a female dog. Instead, be knowledgeable and have an informed discussion with your vet.