04/19/2025
Many clients wonder about when to spay/neuter their pet. I personally would never do it before 1 year old, because I've learned enough to know that physically and behaviorally it is better for them and can avoid future issues. I always advise clients to get their vet's suggestion and do your own research on what's best for your pet.
Monday Medical Corner:
Ovariohysterectomy, popularly known as ‘spaying’, is commonly performed on female dogs as a means of sterilization and to reduce risk of certain diseases including mammary tumors and pyometra (uterine infection). Recent evidence suggests that delaying this procedure until the dog is more mature (at ~18-24 months of age) offers behavioral, orthopedic, and other health benefits.
Dogs’ reproductive cycle is different than that of humans’. A dog’s estrous cycle includes multiple stages. The best known phase is proestrus/estrus or when the dog is in “heat.” This is the phase where the dog ovulates and can become pregnant if she is bred. This phase lasts about 3 weeks on average. The dog then enters diestrus – the phase of pregnancy. What is interesting about dogs is that the hormonal profile in diestrus is the same whether the dog is actually pregnant or not. During this phase, estrogen declines and progesterone rises (secreted from a structure called the corpus luteum [CL]). Progesterone is the hormone that maintains pregnancy. Diestrus in dogs lasts about 2 months – the average duration of gestation when the dog is pregnant. At the end of diestrus, the CL essentially dissolves or becomes inactive and progesterone levels drop. If the dog is pregnant, this change is part of the process that triggers the birth of the puppies and onset of lactation and maternal behavior.
After diestrus, the dog enters anestrus which is a period of hormonal quiescence. In the dog this lasts on average about 6 months as the typical complete estrous cycle in dogs is about 7-9 months long.
If a dog is spayed during diestrus, the precipitous drop in progesterone can mimic whelping and trigger the onset of maternal behavior – including maternal aggression. Since the dog does not have puppies, dogs may begin to guard other objects and show aggression toward humans or other animals. In rare cases, this aggression has persisted long term.
Since there is no benefit to spaying a dog during diestrus, we recommend that dogs be spayed during anestrus to prevent this possible complication.
