Spaying After a Season: Does the Timing Matter?
Vets usually wait three months after a season to spay. Records from 2,543 assistance-dog bitches suggest an earlier window, with caveats for pet dogs.
Written by thecanineledger
Most vets advise spaying a female dog in the quiet phase of her cycle, usually at least three months after a season. The reasons are a lower risk of bleeding during surgery and of a false pregnancy afterwards. A 2026 study of 2,543 bitches in a large UK assistance dog programme tested an earlier window, in the weeks just after a season ends (Moxon & England, Frontiers in Veterinary Science 2026).
While the early window looked as safe as the usual one, the riskiest time was in between. The study also has limits for pet owners.
→ When to Spay or Neuter: What the Breed Studies Show, and What They Don’t
1. Why timing matters
Bleeding. During and just before a season, the womb and ovaries have a rich blood supply. Surgery then may carry more risk of bleeding.
False pregnancy. After a season, a hormone called prolactin rises. Removing the ovaries while it is high can trigger a false pregnancy, with signs such as milk production.
The usual advice. For these reasons, vets usually wait until the quiet phase. The authors describe this as usually starting at least 90 days after ovulation.
2. The study
The dogs. The researchers used records from a large UK assistance dog organisation, covering bitches spayed from 2018 to 2024. All were large breeds or crossbreeds.
Three windows. Each bitch was grouped by how long after her estimated ovulation she was spayed:
| Window | Days after estimated ovulation | Bitches |
|---|---|---|
| Early | End of season to day 43 | 319 |
| Riskiest | Days 44 to 89 | 231 |
| Usual | 90 days or more | 1,993 |
Estimating ovulation. Ovulation was estimated as seven days before the end of the season.
Funding. The authors declare no financial support and no conflicts of interest. The first author works for the organisation whose dogs were studied.
Our note: Estimating ovulation from the end of a season isn’t exact, and you may not know when a season ends.
3. What it found
Bleeding. Spaying window wasn’t linked to bleeding during surgery. Excluding minor bleeding from the skin and fat, bleeding was reported in 3.8% of early, 5.8% of usual and 7.4% of riskiest-window bitches.
False pregnancy. Only six cases were found in the health records after spaying: two early, one usual and three riskiest-window bitches. That is too few to test statistically.
Behaviour. Records of fear, anxiety or aggression in the six months after spaying were more common in the riskiest window (20.8%) than in the usual (11.7%) or early (4.1%) windows.
The authors conclude that spaying in the early window “may be a suitable alternative to the ‘conventional’ period.” They add that the results support the advice to avoid the riskiest window.
Our note: The abstract says six false pregnancies after spaying, but the results report seven.
4. What the study can’t tell you
Pet dogs. The authors write that the study “included only large and cross breed bitches from an assistance dog organisation’s population.” Results may differ for other breeds.
Missed cases. Bleeding was only recorded if the surgeon noted it, and false pregnancies showing only as behaviour change may have been missed.
Not a trial. Bitches weren’t randomly assigned to a window.
Our note: The paper doesn’t say whether vets should confirm the stage of the cycle before an early spay in pet dogs.
5. If you’re planning a spay
- Ask your vet when they advise, and why.
- Tell your vet the dates of her last season.
- Ask about the early window if waiting is a problem, but expect your vet to judge it case by case.
Our note: These points are ours, not the study’s.
→ Pyometra: The Emergency in Unspayed Females
6. What we could not verify
| Commonly said | What we found |
|---|---|
| “Never spay until three months after a season” | Not settled. An earlier window looked as safe in assistance dogs. |
| “Spaying after a season always causes false pregnancy” | No. Only six cases were recorded in 2,543 bitches. |
| “The timing doesn’t matter” | Not shown. The window between 44 and 89 days looked worst. |
Sources
- Moxon R, England GCW. Retrospective study examining complications and iatrogenic pseudopregnancy in bitches neutered in different stages of the oestrous cycle: identification of an ‘early neutering window’ in bitches. Front Vet Sci 2026: records of 2,543 bitches in a UK assistance dog programme, 2018 to 2024. No financial support
Always confirm with your vet before acting on anything on this page.