What age does the periods stop for a dog?

Dogs do not have menstrual periods like humans do. They instead go through something called an estrous cycle, which is a reproductive cycle that involves four stages: proestrus, estrus, diestrus, and anestrus. The length of the estrous cycle varies between breeds and individual dogs, but it typically lasts around 21 days.

During the proestrus stage, the female dog's body begins to prepare for ovulation. This stage is characterized by swelling and discharge from the vulva, as well as increased urination. The estrus stage is the fertile period of the cycle, during which the female dog is most likely to become pregnant. This stage is characterized by a bloody discharge from the vulva, as well as increased receptivity to males. The diestrus stage is the luteal phase of the cycle, during which the corpus luteum (a small gland that forms on the ovary after ovulation) produces progesterone. This hormone helps to maintain the uterine lining and prepare it for pregnancy. The anestrus stage is the resting phase of the cycle, during which the female dog's body returns to its normal state.

The age at which a dog's estrous cycles stop varies between breeds and individual dogs. However, most dogs will stop having cycles by the time they are 10-12 years old.