When should you spay a female dog? Major review finds the science on puberty timing is thin

A new review in PLOS ONE delivers a surprising message to dog owners and veterinarians: despite decades of research on spaying, there is still no robust evidence to say whether it is healthier to neuter a female dog before or after puberty. The scoping review—designed to map what’s known and identify gaps—concludes that the impact of spaying relative to first heat on allergies, joint development, cancers, obesity, and urogenital health remains unclear, leaving families and clinicians without firm, evidence-based timing recommendations.

To reach that conclusion, researchers systematically searched CAB Abstracts, Medline, and Web of Science, screening 1,145 publications and retaining 33 for detailed analysis. Yet only six of those studies actually categorized spaying as pre‑pubertal versus post‑pubertal, and they focused almost entirely on mammary tumors (one study) and urogenital outcomes such as urinary incontinence (five studies). No studies directly compared pre‑ versus post‑puberty spaying for atopy (allergic disease), developmental orthopedic disease, or obesity. Most of the remaining 26 studies grouped dogs by age at surgery rather than by true pubertal status.

That distinction matters. Puberty in dogs is typically defined by the first oestrus (heat), and its timing varies widely—from about six to 18 months—depending on breed and other factors. Using age as a stand‑in for puberty can misclassify animals, and the review found examples where “pre‑pubertal” dogs were as old as 1.4 years and “post‑pubertal” dogs were as young as 0.3 years. With inconsistent definitions and age bands across studies, it becomes difficult to compare findings or draw reliable conclusions about the specific question owners care about: before or after first heat.

The broader literature on age at spay—while not a perfect proxy for puberty—has reported mixed health effects. Earlier spaying has been associated in some studies with higher risk of certain orthopedic problems, like cranial cruciate ligament rupture, but lower risk of some cancers such as mammary neoplasia and mast cell tumors. Even within single outcomes, results can conflict; for urinary incontinence, some studies suggest earlier spaying increases risk, others suggest the opposite, and several find no clear association. The authors emphasize that because these findings are age‑based rather than puberty‑based, they cannot settle the puberty‑timing debate.

The evidence base itself shows important limitations. Of the 33 included papers, most were from North America and varied widely in design, with many relying on veterinary records or owner questionnaires rather than standardized clinical assessments. Many studies did not report the type of surgical procedure performed, did not separate male and female results, and did not account for prior breeding history, even though pregnancy might influence later health risks. Follow‑up periods often differed or were too short to capture diseases that emerge in middle or older age. In some cases, researchers did not exclude dogs that already had the disease before surgery, making it impossible to attribute risk to spaying.

Taken together, these gaps explain why the review stops short of giving a clear‑cut answer. The authors argue that future studies should prospectively record true pubertal status (i.e., the first oestrus), standardize definitions and surgical reporting, control for breed—since both disease risks and the age of puberty vary by breed—and follow dogs long enough to capture conditions that appear later in life. They also call for clearer diagnostic criteria and pre‑surgery health status, so researchers know whether a condition developed after spaying or was already present. Without these steps, the field will continue to generate data that are suggestive but not decisive.

For owners facing the spay decision today, the review’s practical message is to avoid one‑size‑fits‑all rules and work closely with a veterinarian who can weigh individual factors. Breed and expected adult size, lifestyle and roaming risk, local disease prevalence, and family priorities all matter. Spaying prevents pyometra (a life‑threatening uterine infection) and unwanted litters, but timing may involve trade‑offs that differ from one dog to the next. Until stronger evidence arrives, individualized advice remains the safest path.

The study also serves as a roadmap for the scientific community. By highlighting exactly where data are thin and how current study designs fall short, it sets a research agenda that could, within a few years, deliver the kind of clear, puberty‑specific guidance that owners and veterinarians have long wanted. For now, the science acknowledges its limits—and invites better answers.

^{Source: Moxon R, England GCW, Payne R, Corr SA, Freeman SL (2024). Effect of neutering timing in relation to puberty on health in the female dog – a scoping review. PLOS ONE. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0311779}