Spaying Your Female Dog: Medical Facts, Behavior, and Practical Management

In brief

There are four things you should know before you decide. First, the frequently cited protection against mammary tumors from early spaying is less clearly supported by the science than many simplified accounts suggest—a systematic review explicitly rates the evidence as weak. Second, when it comes to behavior, the studies contradict each other: owner surveys find associations, while the only prospective cohort study in female dogs found none. Third, there is a measurable association with timing—in a British analysis, females spayed later had 20 percent lower odds of early-onset urinary incontinence. And fourth, there are clear medical indications where the question doesn't even arise.

Deciding whether to have a female dog spayed is one of the most emotional questions in life with a dog—and one surrounded by more half-knowledge than almost any other. In this article, we go through what the data actually show, where they are thinner than claimed, and how you can confidently guide your female dog through her cycles without surgery.

👉 Dog health basics: preventive care and health checks

1. What happens during spaying

Spaying removes either the ovaries (ovariectomy) or the ovaries together with the uterus (ovariohysterectomy). Afterward, the female is permanently unable to reproduce, and the ovarian production of sex hormones stops.

This is not a minor procedure. With the loss of sex steroids, the higher-level hormonal regulation changes: because the feedback from the ovarian hormones is missing, the pituitary hormones LH and FSH rise and remain permanently elevated. Researchers discuss this rise as one possible mechanism linked to the risk of urinary incontinence (Reichler et al., 2005).

For context: according to current knowledge, whether an ovariectomy or an ovariohysterectomy is performed makes no proven difference to the risk of incontinence.

Procedures and alternatives

Laparoscopic ovariectomy. Smaller incisions, generally less pain, and faster healing.

Ovary-sparing hysterectomy. The uterus is removed while ovarian function is preserved. The female can no longer become pregnant but keeps her hormonal balance. Important for setting expectations: heat cycles continue, including their attraction for males, and any influence of the hormones on mammary tumor risk also remains. The procedure is uncommon and not available at every practice.

GnRH implants, for example with deslorelin. A temporary hormonal option that can be used in individual cases to assess hormonal effects before an irreversible decision is made. Veterinarians use deslorelin implants in female dogs in certain cases, but this is not equivalent to a regular spay, and whether and how it is used depends on the indication and the regulatory situation, as judged by the treating veterinarian.

A realistic note on the "trial phase": the implant does not exactly reproduce the state after spaying. It starts with an initial stimulation phase, and how long it works varies from dog to dog. It is useful as a guide, not as a guarantee.

2. When spaying is medically indicated

There are situations in which the trade-off is clear:

• Pyometra (uterine infection): a life-threatening condition that requires prompt surgery.
• Tumors of the ovary or uterus.
• Severe, recurrent false pregnancies causing considerable distress, once management and veterinary treatment have been exhausted.
• Certain hormone-dependent diseases after a veterinary workup.

This is not about training; it is about the female dog's health. That decision is made by the veterinarian, not by the dog trainer.

Depending on where you live, animal welfare law may also set rules for when spaying a healthy dog is permitted. Your veterinarian will know which rules apply in your area.

3. Mammary tumors: the most overstated point

Few statements are passed on as matter-of-factly as this one: spaying before the first or second heat drastically lowers the risk of mammary tumors. The numbers behind it come from a 1969 paper that reported a relative risk of 0.005 for spaying before the first heat, 0.08 after one heat, and 0.26 after two or more heats.

This body of research has been systematically reviewed according to Cochrane criteria. Of more than 11,000 hits, 13 English-language papers that had examined the association remained. The conclusion was clear: because of the limited amount of data and the risk of bias in the published results, the evidence both that spaying reduces the risk of mammary tumors and that timing plays a role should be rated as weak and is not a sound basis for firm recommendations (Beauvais et al., 2012a).

Criticisms of the 1969 paper included that cases and controls were recruited from different time periods and that confounders were not adequately accounted for.

A clarification on the word "weak," because it is easily misunderstood: it is the term the review itself uses, and it refers to the quality of the evidence—study design, sample sizes, and risk of bias—not to the size of any effect. A weak evidence base can hide a strong effect just as well as no effect at all. That is exactly the point: we don't know.

What this means in practice: it does not mean the effect doesn't exist. It means nobody can seriously claim to know it—and that "before the second heat" is not a reliable deadline. If someone presents this point to you as the decisive argument, it is worth asking questions.

4. Behavior: where the studies contradict each other

The most important sentence first, because it helps most in everyday life: spaying is no substitute for training. It doesn't solve fear problems, doesn't fix insecurity, and doesn't change learned behavior patterns. Behavior that developed through learning doesn't disappear through surgery.

That is not to say hormones play no role. They change the likelihood that a behavior will occur, and in some females there are cycle-dependent patterns that cannot be trained away. The point is a different one: even behavior that hormones made more likely was performed and practiced—and what has been practiced remains available when the hormonal push goes away.

In practice, this means the procedure may change one part but not the other. How large each part is cannot be determined in advance, and that is exactly what makes spaying an unreliable measure against an existing behavior problem.

On the question of whether spaying can increase fearfulness or aggression, however, the data are more inconsistent than many guides—including animal-welfare-oriented ones—suggest.

What owner surveys show. In an analysis of 8,981 spayed females using the standardized C-BARQ questionnaire, 23 behaviors differed between intact and spayed dogs. A longer lifetime under the influence of gonadal hormones was associated with significantly fewer reports of ten mostly undesirable behaviors—including one in the area of fearfulness and three in the area of aggression. Conversely, chewing and howling were more frequent with longer hormone exposure (Starling et al., 2019).

What the prospective study shows. In the only prospective cohort study on this topic to date, 306 Labrador/Golden Retriever cross females were spayed either before puberty at six months or after their first heat. Six behavioral domains were assessed—trainability, aggression, fear and anxiety, excitability, attachment, and social behavior—at one and at three years of age. The result: no effect of spay timing on any of the six domains (Moxon et al., 2022).

Why this need not be a contradiction. Owner surveys are snapshots and cannot resolve the direction of an effect. Does a female become more fearful because she was spayed—or was she spayed because she showed problem behavior? Both produce the same correlation. The prospective study gets around this problem, but it looks at only two closely related breeds raised under very uniform conditions and cannot simply be generalized to other dogs. The authors of the prospective study themselves note that findings vary considerably between studies and that the associations remain unclear for many behaviors.

Our assessment for practice: spaying is not a reliable measure against insecurity or aggression, and there are indications that in individual cases it may work in the opposite direction. That is a reason to be cautious with fearful females—but not a reason to claim that spaying makes females fearful. Anyone who plays one against the other is working not with the evidence but against it.

If behavior is the real issue, the first step is an analysis: is the cause hormonal, pain-related, learned, or environmental? That question can be answered—and before any surgery.

For our consultations as dog trainers, we draw a simple sequence from this. When a female is brought to us because of a behavior problem and spaying is being considered, we first clarify which behavior is meant and when it occurs. In most cases, a pattern emerges that has nothing to do with the cycle—and then spaying is not an option but a distraction.

If, on the other hand, there is a clear cyclical link, that is a reason to talk to the veterinarian—but still no guarantee that the procedure will change the behavior. Whatever occurs more often during the cycle has also been practiced more often during that time.

5. Joints and growth: the numbers behind the claim

The statement "Early spaying delays the closure of the growth plates and increases the risk of cruciate ligament tears and hip dysplasia" is part of the standard repertoire. It deserves a closer look.

The mechanism is plausible: estrogen inhibits the growth hormone–IGF axis and is involved in closing the growth plates once skeletal maturity is reached. If it is lost early, prolonged growth in length would be expected.

The chain of evidence, however, is thinner than the matter-of-fact tone suggests. As the authors of the prospective cohort study point out, most of the sources that are cited are reviews drawing on a single dog study—with seven females in the group spayed at seven weeks, four in the seven-month group, and six intact animals. A second study in female dogs found no significant differences in bone length (Moxon et al., 2023).

In the prospective study itself, the females spayed before puberty grew significantly more in height between the sixth and seventeenth month (6.5 vs. 4.4 cm). However, the absolute difference in height and weight at 17 months was not significant (58.5 vs. 56.6 cm; 28.3 vs. 27.3 kg). The authors explain this by the fact that dogs in both groups were spayed only after the main growth phase.

And the sentence that is decisive for the joint question: according to the same paper, there is no research directly examining the effect of spaying before versus after known puberty on hip dysplasia or other musculoskeletal diseases (Moxon et al., 2023). Studies on spaying and joint disease mostly look at age without recording pubertal status.

Bottom line on this point: an association between very early spaying and joint problems is biologically plausible and supported by observational data, but the common portrayal as an established, quantified causal relationship goes beyond the evidence—especially for spays that take place after the main growth phase anyway.

6. Urinary incontinence: better numbers than the ones in circulation

The figure "5 to 20 percent of spayed females become incontinent" is widely circulated. It comes from older studies, some of them conducted in referral populations. Newer, population-based data paint a different picture:

• In primary veterinary care in England, the prevalence of urinary incontinence across intact and spayed females combined was 3.14 percent (O'Neill et al., 2017).
• In a case-control study, spayed females had 3.01 times the odds of an incontinence diagnosis compared with intact females (Pegram et al., 2019).
• On timing: in an analysis of 1,500 females using a method that emulates a randomized trial, females spayed later (7 to 18 months) had 20 percent lower odds of early-onset incontinence than those spayed early (3 to under 7 months); odds ratio 0.80, confidence interval 0.54 to 0.97 (Pegram et al., 2024).

Honesty requires the caveat that the authors themselves name: the calculated E-value of 1.81 means that an unmeasured confounder of moderate strength could, mathematically, explain away this association. The association with spaying itself is considerably stronger than the association with timing.

An older systematic review concluded that there is weak evidence of a decreasing risk with increasing age at spaying up to about twelve months, but not beyond (Beauvais et al., 2012b).

When comparing these figures, keep one thing in mind: they come from different populations and use different case definitions. The low prevalence of 3.14 percent comes from primary veterinary care, so it covers females that were seen for any reason at all. The older, considerably higher figures come partly from referral populations, in which incontinence cases are overrepresented, and partly from owner surveys, which also count mild cases that were never seen by a veterinarian.

Which number is "right" therefore depends on what is being counted. For estimating your own dog's risk, the population-based figure is the more appropriate one; for the question of how many females ever show any form of leakage, it is probably too low.

Of practical relevance: incontinence is usually permanent, can usually be managed well with medication, and comes with lifelong costs.

7. A point missing almost everywhere: vulvar conformation

If a female is spayed before puberty, she misses the estrogen surge that makes the external genitalia mature. In the prospective cohort study, significantly more of the females spayed before puberty had a vulva assessed as juvenile or recessed at 17 months; in the blinded assessment of digital images, the figures were 71.1 vs. 46.3 percent (Moxon et al., 2023).

Why this matters: a recessed or juvenile vulva comes with more skin folds in which urine and bacteria can collect. This has been linked to skin inflammation around the vulva, urinary tract infections, bladder infections, and vaginitis.

For context: the study itself does not derive a contraindication against early spaying from this, but calls for the long-term consequences to be studied before recommendations are made. It is an argument for care in choosing the timing, not for panic.

8. Other risks—weighed honestly

Weight gain. Energy requirements drop. Without adjusted feeding, weight gain is a real risk—this is the most manageable point and at the same time the most frequently underestimated one.

Certain types of tumors. For individual tumor types such as hemangiosarcoma and transitional cell carcinoma of the bladder, observational studies have described associations with neuter status. These findings depend on breed and don't allow a simple statement about cause and effect. We deliberately give no numbers here: a single figure such as "three times higher" without breed, age, and study design would be

falsely precise.

Breed differences. Risk profiles differ considerably between breeds and size classes. That is why a blanket age recommendation is not professionally defensible—the decision belongs with the individual female dog.

9. Pyometra: the condition behind the strongest argument

Uterine infection is listed in section 2 as a medical indication, and it is the weightiest single argument for spaying. Because it has to be recognized quickly when it occurs, it deserves more detail than a bullet point.

9.1 What happens

After every heat, the uterus is under the influence of the corpus luteum hormone—the lining builds up and the cervix closes. This combination favors bacteria. If they get in, pus can accumulate in the uterus.

If the cervix stays open, some of it drains out and becomes visible. If it stays closed, everything accumulates inside—this is the more dangerous form, because the most obvious sign is missing.

9.2 How to recognize it

The typical window is four to eight weeks after the heat. That is the single most important clue: if you keep a record of the heats, you will interpret symptoms in this window differently.

Signs include increased drinking and urination, lethargy, loss of appetite, a distended abdomen, fever, vomiting—and, in the open form, purulent or bloody-purulent vaginal discharge.

The first sign is often increased thirst, and it is easily overlooked because on its own it seems unremarkable. A female who drinks noticeably more than usual six weeks after her heat and is more listless than usual needs to be examined—even without discharge.

9.3 Why this shifts the balance

Pyometra is a surgical emergency and mainly affects older, intact females. It is therefore the argument that gains weight as the dog gets older—unlike the points in sections 3 to 7, which mainly concern early timing.

In practice, this means that deciding against spaying in the second year of life is not a decision for life. The answer may be different at eight or ten years of age, and for a different reason than at two.

10. The surgery and the time afterward

A medical decision is not yet a practical plan. Three questions come up in every consultation.

10.1 When in the cycle

Elective procedures are usually scheduled during anestrus, the resting phase between two heats. During heat, blood flow to the reproductive organs is markedly increased, and immediately afterward the female is under the influence of the corpus luteum hormone.

In practice, that means an interval of several weeks to months after the last heat—the practice sets the exact date. If you are planning a spay, you should therefore keep a record of the heats; without that date, planning is impossible.

10.2 The time after the procedure

Expect roughly ten to fourteen days until the stitches come out, and a rest period of about the same length: no rough play, no jumping, no off-leash time, short walks on leash, no swimming, and no bathing.

Wound protection is where things tend to go wrong in everyday life. Most females accept a recovery suit better than a cone, but it has to be changed consistently when she relieves herself. What matters is that protection has no gaps: a single unsupervised half hour can be enough to open a suture.

Take your dog back to the practice if there is swelling, redness, warmth, or discharge at the incision, loss of appetite beyond the first day, fever, or apathy.

10.3 Weight—the point that really needs managing

Energy requirements drop after spaying, and they do so fairly soon. If you leave the food ration unchanged, you risk weight gain—that is not an unavoidable side effect but a matter of arithmetic.

What has proven useful: write down her weight before the procedure, reweigh every two to four weeks afterward, and adjust the amount as soon as the weight goes up instead of waiting. If you only act once the waistline has disappeared, you will have three kilos to lose instead of three hundred grams.

This point matters so much because excess weight amplifies several of the risks from the previous sections—and because it is the only one of them that is entirely in your hands.

11. Practical management of the cycle

Before spaying is considered, the first step is to guide your dog confidently through her natural cycles. Much of what is perceived as a "problem" is a question of management.

The phases

The following figures are rough guides with considerable individual variation—the intervals between heats and the length of the phases differ markedly between individual females and between breeds.

Phase	Duration (approx.)	Characteristics
Proestrus	3–17 days	Vulva swollen, bloody discharge, males show interest, female does not yet accept them
Estrus ("standing heat")	3–14 days	Discharge becomes lighter, female accepts males, fertile phase
Diestrus (metestrus)	60–90 days	Luteal phase after heat, possible false pregnancy
Anestrus	several months	Resting phase between two heats

A clarification on anestrus: this phase is often described as a "resting phase without hormonal activity." But a resting cycle doesn't mean hormonal silence—the next cycle is being prepared during this time. In practice, this mainly means that anestrus is considered the period in which an elective procedure is usually scheduled.

No off-leash time during standing heat

As soon as the female enters estrus, reliable off-leash time is no longer a given. Even a female who otherwise comes back reliably may respond differently during this phase. Sensible options are secure, fenced areas without access for males, or consistent leash walking.

We describe how to make leash walks relaxed in our guide to loose-leash walking .

Group classes: arrangement rather than rule

A female in heat generally doesn't belong in regular group classes during that time. This is not a judgment of the dog but a question of training quality: for many dogs, especially intact males, the situation is a considerable distraction, and the female's own ability to concentrate may be altered as well. Make-up sessions, private lessons, or adapted settings are then usually the better solution.

The same applies the other way around: highly aroused males, or males who are no longer responsive, are often not suited to a group in such situations either. What matters is not sex or neuter status but the actual responsiveness of the individual dog, the composition of the group, and the training goal. For spayed females, too, participation should therefore never be judged across the board.

Regular checks

Get into the habit of looking at the vulva regularly around the time a heat is expected. Swelling, redness, and discharge give you clues about where she is in her cycle. Foul-smelling or purulent discharge, marked swelling outside the cycle, increased drinking, lethargy, or loss of appetite in the weeks after a heat should be checked by a veterinarian right away—these can be signs of a uterine infection.

False pregnancy

In the second half of the cycle, the body naturally produces progesterone. Many females then show a hormonally driven false pregnancy: restlessness, nesting behavior, mothering objects, milk production, increased clinginess, or irritability.

What helps: calm, avoiding stimulation of the mammary glands, redirecting activity rather than taking away the objects she is mothering. No hormonal products on your own initiative. If she is clearly distressed, she should be seen by a veterinarian—repeated, severe episodes are one of the understandable reasons to consider spaying.

We cover this topic in detail in our guide to false pregnancy in dogs .

12. Decision guide

Four questions that usually settle the matter:

Is this about health or about making everyday life easier? Both are legitimate motives, but they deserve different trade-offs.

Is the problem really hormonal? Fear, insecurity, leash reactivity, and impulse-control problems usually aren't.

Have training and management been exhausted? Managing two heats safely takes effort, but it is reversible. Spaying is not.

How urgent is it? With pyometra, the question is settled. Otherwise, you have time for a careful decision—and anestrus is the usual period for a planned procedure.

13. Conclusion

Spaying a female dog can make sense. It is not a blanket recommendation—in either direction. Anyone who presents it as routine overstates the benefits; anyone who presents it as fundamentally harmful overstates the risks.

What the data support: there are clear medical indications. The protection against mammary tumors is weakly supported. Timing shows a measurable but moderate association with the risk of incontinence. On behavior, survey studies and the only prospective study contradict each other. And no surgery solves behavior problems that developed through learning.

Good decisions come from combining a veterinary assessment with an honest behavior analysis—not from myths, convenience, or the feeling that "that's just what you do."

For the evidence on neutering and behavior beyond female dogs, see Neutering and Behavior in Dogs: What the Evidence Shows .

A note on the evidence

The veterinary statements in this article are based on peer-reviewed papers, mostly from British practice databases and from a prospective cohort study in Labrador and Golden Retriever crosses. The prospective study is methodologically the strongest, but it covers only two closely related breeds raised under uniform conditions—its applicability to other dogs is limited.

The owner surveys using the C-BARQ questionnaire cover very large numbers of dogs but cannot resolve the direction of an effect. Both study types are labeled as such in the text.

And the sentence that stands above everything else: there is no blanket right answer and no universally valid age recommendation. What there is, is a weighing-up for this female, in this situation, with this history—and a few common arguments that support this weighing-up less than they claim to.

Key takeaways on spaying female dogs

The protection against mammary tumors is less well supported than claimed. A systematic review according to Cochrane criteria rates the evidence both for the protective effect and for the role of timing as weak (Beauvais et al., 2012a). "Before the second heat" is not a reliable deadline.

On behavior, the studies contradict each other. Owner surveys find associations (Starling et al., 2019); the only prospective cohort study found no effect of timing on six behavioral domains (Moxon et al., 2022). Both can be true—surveys cannot resolve the direction of an effect.

Spaying is no substitute for training. Even hormonally influenced behavior was performed and practiced, and what has been practiced remains available.

The joint claim rests on a very small basis. There is no direct study of spaying before versus after puberty and its effect on hip dysplasia or other musculoskeletal diseases (Moxon et al., 2023).

The incontinence figures in circulation are too high for primary care. In English primary veterinary care, the prevalence across intact and spayed females combined was 3.14 percent (O’Neill et al., 2017); spayed females had 3.01 times the odds (Pegram et al., 2019).

Timing shows an association—a small one. Females spayed later had 20 percent lower odds of early-onset incontinence (Pegram et al., 2024). The association with spaying itself is considerably stronger than the association with timing.

Vulvar conformation is missing from almost every account. In females spayed before puberty, the vulva was more often assessed as juvenile or recessed at 17 months—71.1 vs. 46.3 percent (Moxon et al., 2023).

Weight is the only risk that is entirely in your hands. Energy requirements drop fairly soon; if you don't adjust the ration, you risk weight gain.

Pyometra gains weight with age. A decision against spaying in the second year of life is not a decision for life.

References

• Beauvais, W., Cardwell, J. M., & Brodbelt, D. C. (2012a). The effect of neutering on the risk of mammary tumours in dogs – a systematic review. Journal of Small Animal Practice, 53(6), 314–322. https://doi.org/10.1111/j.1748-5827.2011.01220.x
• Beauvais, W., Cardwell, J. M., & Brodbelt, D. C. (2012b). The effect of neutering on the risk of urinary incontinence in bitches – a systematic review. Journal of Small Animal Practice, 53(4), 198–204. https://doi.org/10.1111/j.1748-5827.2011.01176.x
• Moxon, R., Freeman, S., Payne, R., Corr, S., & England, G. C. W. (2022). A prospective cohort study investigating the behavioural development of bitches in a guide dog training programme neutered prepubertally or post-pubertally. Frontiers in Veterinary Science, 9, Article 902775. https://doi.org/10.3389/fvets.2022.902775
• Moxon, R., Freeman, S. L., Payne, R., Godfrey-Hunt, J., Corr, S., & England, G. C. W. (2023). A prospective cohort study investigating the impact of neutering bitches prepubertally or post-pubertally on physical development. Animals, 13(9), Article 1431. https://doi.org/10.3390/ani13091431
• O'Neill, D. G., Riddell, A., Church, D. B., Owen, L., Brodbelt, D. C., & Hall, J. L. (2017). Urinary incontinence in bitches under primary veterinary care in England: Prevalence and risk factors. Journal of Small Animal Practice, 58(12), 685–693. https://doi.org/10.1111/jsap.12731

• Pegram, C., O'Neill, D., Church, D., Hall, J., Owen, L., & Brodbelt, D. (2019). Spaying and urinary incontinence in bitches under UK primary veterinary care: A case–control study. Journal of Small Animal Practice, 60(7), 395–403. https://doi.org/10.1111/jsap.13014
• Pegram, C., Diaz-Ordaz, K., Brodbelt, D. C., Chang, Y.-M., Hall, J. L., Church, D. B., & O'Neill, D. G. (2024). Later-age neutering causes lower risk of early-onset urinary incontinence than early neutering – a VetCompass target trial emulation study. PLOS ONE, 19(7), Article e0305526. https://doi.org/10.1371/journal.pone.0305526

• Reichler, I. M., Hung, E., Jöchle, W., Piché, C. A., Roos, M., Hubler, M., & Arnold, S. (2005). FSH and LH plasma levels in bitches with differences in risk for urinary incontinence. Theriogenology, 63(8), 2164–2180. https://doi.org/10.1016/j.theriogenology.2004.09.047

• Starling, M., Fawcett, A., Wilson, B., Serpell, J., & McGreevy, P. (2019). Behavioural risks in female dogs with minimal lifetime exposure to gonadal hormones. PLOS ONE, 14(12), Article e0223709. https://doi.org/10.1371/journal.pone.0223709

Note: This article does not replace veterinary advice. The decision about spaying, its timing, and the procedure belongs in a conversation with your veterinarian.

Frequently asked questions about spaying female dogs

What people ask most often in consultations