I've heard of bitches becoming pregnant on the 21st day, so keep an eye on her for another week or so, but you should be coming to the end.
"Stages of the Estrous Cycle
Proestrus: Vulvar swelling and bloody vaginal discharge marks the beginning of proestrus.The first day of bleeding is called the first day of heat. The duration of proestruscan vary from as little as 1 day to 21 days. Proestrus is a time of rising estrogenlevels preparing the reproductive tract for breeding.
Estrus: Is the period of receptivity. Behaviorally it begins the first day the bitch stands. Hormonally it begins on the day of the LH surge and is marked by rising progesterone levels and decreasing estrogen levels.
Diestrus: Normally begins 7 to 9 days post the actual LH surge. Progesterone levels continue to rise and the vaginal cytology cornification abruptly declines. The diestrus period lasts until the bitch whelps or the serum progesterone returns to a basal level.
Anestrus: Is the period of time between the end of diestrus and the next proestrus period." |