During the heat cycle of the female canine, the vulva swells and opens to about 3 times it's non-estrus size. The first signs of heat (canine reproductive cycle) are slight swelling with blood discharge ranging from light, spotting, to a heavier bleeding similar to human females. As her cycle progresses, the discharge usually changes from red to clear, or whitish. The swelling is very visible and should not be interpreted as a problem. If you are positive your female is in her heat cycle, watch for any signs of yellow or green thick discharge. This is a warning sign of something more serious, and would require immediate medical attention. The vulva swelling lasts from 10-25 days. For more information on normal cycles, breeding and spaying, see me at liveperson. Just type me in the search bar!