What Is Spay (Ovariohysterectomy / Ovariectomy)?
Spaying is the surgical sterilisation of female dogs and cats through the removal of the ovaries (ovariectomy) or ovaries and uterus (ovariohysterectomy). It prevents reproduction, eliminates heat cycles, and provides significant health benefits including complete prevention of pyometra and reduced risk of mammary gland cancer. It is the most commonly performed elective surgery in companion animals.
Understanding Spay (Ovariohysterectomy / Ovariectomy)
The traditional ovariohysterectomy (OHE) removes both ovaries and the uterus. The increasingly favoured ovariectomy (OVE) removes only the ovaries. Evidence suggests that removing the ovaries alone is sufficient — without hormonal stimulation, the remaining uterus does not develop disease — and the procedure is simpler and faster. Both approaches have excellent safety records when performed by a qualified surgeon.
Health benefits are well-established. Spaying eliminates pyometra (uterine infection) risk — a frequently life-threatening emergency in intact females over 4 years of age. Mammary gland cancer risk is reduced by approximately 91% when spaying occurs before the first heat cycle, 79% if performed after the first heat, and 74% after the second heat. The benefit diminishes beyond the second heat, though spaying at any age still eliminates pyometra risk.
For most cats and small to medium breed dogs, spaying around 5–6 months of age — before the first heat — provides maximum health benefits. For large and giant breed dogs, delaying until 12–18 months or later may reduce the risk of certain orthopaedic conditions; the evidence is breed and size-specific, and a conversation with your veterinarian about your specific dog is recommended.