Do dogs get periods?

Dogs do not get menstrual periods like human beings, but they have what is called an estrus cycle. This cycle involves a period of false pregnancy during which the dog can start producing milk.

Also known as pseudopregnancy, false pregnancy can last for weeks and usually becomes unpredictable with age. The initial phase is called proestus. The dog experiences a swollen vulva and a bloody discharge. It is this vaginal discharge that creates the myth that dogs menstruate. The second phase is referred to as estrus. The color of the vaginal discharged becomes straw colored. The female allows the male dogs to mount at this stage.