Some dogs develop slightly swollen nipples and teats before or during their heat cycle. It can also take some time for the swelling to disappear.
Note: If you notice your dog’s teats staying swollen AFTER the heat cycle, don’t panic right away. It can be normal. With Mila it once took several months before her teats had developed back to normal.
It is very common for the vulva to become quite swollen during a heat cycle. However this is sadly no cast-iron sign, because some dogs’ vulvas hardly swell at all.
Male dogs getting interested
Male dogs will become interested in your dog before she is even fertile. If you notice a sudden increased interest of males, that’s the time to start taking precautions.
Most male dogs (especially those who are not seasoned or experienced studs) will get excited to breed with a female at any time during her heat cycle. Although a female will instinctively attract males to her by marking her area by means of urinating in many small spots within her boundaries as well as teasing, prancing, and flagging during her proestrus stage, she will not willingly welcome an actual breeding until she is in fact in estrus. For dominant breeds this can lead to a fight due to the female unwilling to allow any male to mount her. For some females they may never willingly allow a male to mount them, which is often why breeders resort to breeding by means of Artificial Insemination (AI) during time of ovulation. A well-seasoned stud actually has the ability to truly determine when a female is ovulating and when she is not. Breeders who own a stud of this caliber find it much easier to know when a female is ovulating and when she is not based on the interest level of the stud. Due to the increased chances of injury or a fight all deliberately scheduled breedings should be supervised at all times.