Updated On February 9th, 2015
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Answered By Laura E. McRae 53
Veterinary Technician
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It is not unusual for the vulva to remain swollen for a period of time after the "heat" cycle is over. In dogs, there are [4 stages of estrus](https://www.petcoach.co/article/anatomy-and-function-of-the-reproductive-system-in-dogs). The combination of proestrus and estrus, which is often referred to as "heat" by breeders, lasts approximately 21 days. "Heat" is followed by diestrus and anestrus. During proestrus, the vulva swells and has a bloody discharge. During estrus, the vulva softens and becomes pliable in preparation for mating. It can take several weeks following estrus for the vulva to shrink back down in size, but it will never go back to the size it was before the first heat cycle. The same is true of the mammary glands, which enlarge slightly in preparation for [pregnancy](https://www.petcoach.co/dog/condition/pregnancy/).
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