The female dog’s estrous cycle is divided into four phases: proestrus, estrus, diestrus and anestrus. Proestrus is the period during which male dogs will be interested in a female dog, but she will not allow them to breed. This is when estrogen is starting to rise, but progesterone is low and typically lasts about nine days. Estrus is the phase when the female dog will not only attract males, but will stand for breeding (standing heat). This is when estrogen starts to decline and progesterone starts to rise rapidly. This phase usually lasts nine days as well. Diestrus is the period that is dominated by the hormone progesterone and is the time of pregnancy maintenance. The female dog is unusual in that this phase lasts about two months, whether she is pregnant or not. Anestrus is a period of low hormone production and cleaning up or uterine involution and preparing for the start of another proestrus. This phase is variable, but it should last two to four months. The typical interestrus interval (time from estrus to next estrus) is six months, but this time can vary from animal to animal and from estrus to estrus in the same animal.
Pregnancy loss is defined as the death of a puppy during the embryonic stage (very early in gestation), to miscarriage of formed puppies mid-pregnancy, to the birth of stillborn puppies. Infections with bacteria like Brucella canis, Campylobacter, Salmonella, E. coli and Strep can cause embryonic or fetal death. Viruses like Distemper, Canine Herpes Virus and Parvo can also cause pregnancy loss. Parasitic infections like Toxoplasma and Neosproa can also cause the loss of pregnancy.
The most common reason for pregnancy failure, however, is poor breeding timing. In other words, the female dog was bred either too early or too late to conceive. There is an optimal time to breed a female dog that lasts four to six days. Identifying this time period can be done using serial progesterone measuring, identifying the LH surge, vaginal cytology (evaluating the cells that line the vagina) and vaginoscopy (visualizing the change in the vaginal mucosa). By evaluating the trends in these parameters over time, you will increase your chance of identifying the optimal times to breed your female dog. Using an experienced, board certified specialist in reproduction will greatly enhance the probability your female dog will become pregnant.
Dr. Deirdre Carver-Raffa is our in-house theriogeologist at Town and Country Animal Hospital and a Board Certified Diplomat of the American College of Theriogenologists. A true reproductive expert, she is the only veterinarian with these credentials in the Naples/ Bonita Springs/ Estero area. If you have any questions about dog pregnancy or any other reproduction issues, from dog dystocia to puppy care, etc., please call our office at (239) 353-5060 to schedule an appointment with Dr. Carver-Raffa.