Whenever a breeding does not result in a successful pregnancy, the fertility of both the male and the female should be assessed. In females, that assessment should include whether the problem was failure to ovulate, failure to conceive, failure of implantation, early embryonic death, fetal resorption, fetal mummification, abortion or something else. It can be challenging, at best, to identify the precise reason why a particular bitch did not conceive or carry a litter to term. Many times, the cause is never determined.
Many breeders bring their bitches to a reproductive veterinarian both before and after they are bred, to properly manage the mating process and increase the chances of success. Determining whether the bitch is pregnant is one of the first steps in diagnosing infertility. A skilled veterinarian or breeder may be able to palpate (feel) puppies by 3 or 4 weeks of age, depending on the size of the breed and of the litter. More commonly, they will conduct an abdominal ultrasound roughly 30 days into the pregnancy, to look for visible fetal heartbeats. Ultrasound is a wonderful way to diagnose a pregnancy or the lack of pregnancy, but it is not particularly reliable as a method to count the number of fetuses and tends to underestimate the ultimate litter size. Also at about 30 days, blood can be drawn to check levels of the hormone relaxin, which can strongly indicate whether or not the bitch is pregnant. One of the most frequently used techniques to diagnose pregnancy is abdominal radiography (X-rays), typically done around day 45 of the pregnancy. X-rays at or after 45 days are a good way to quantify the number of puppies in the uterus, because by that time fetal skeletons are well-enough formed to be separately counted.
When an owner brings a bitch to the clinic to assess her fertility, the veterinarian will take a thorough history that includes her familial and personal reproductive history, her past breeding successes or failures (including the method of breeding and type of semen used – fresh, chilled or frozen), her history of illnesses or injuries and her drug and vaccination background. Diet and dietary supplements will be discussed, as will details of the dog’s living environment such as housing, number of other animals in the household, indoor versus outdoor living and the like. The stud dog’s history should also be explored, including whether he is a recent proven producer of multiple live-puppy litters, his age, his Brucella canis test status and the quality, motility, morphology and concentration of his semen.
The veterinarian will also conduct a thorough physical and reproductive examination. He will digitally examine the bitch’s vagina with a gloved finger to make sure that there are no strictures, constrictions, masses or other physical abnormalities that may be causing pain, interfering with mating or preventing normal passage of sperm and seminal fluid through the cervix into the uterus. Vaginal examination can be quite difficult in tiny toy breeds, for obvious reasons. The veterinarian will examine the patient’s mammary chains for any signs of abnormality or disease. Other common initial diagnostic tests are routine blood work (a complete blood count and serum biochemistry profile) and a urinalysis. The results of those tests will reveal the overall health of the bitch’s organ systems and can also identify the presence of infections that may be contributing to infertility. Unfortunately, sometimes the initial data base results are all unremarkable.
Females suspected of infertility will probably be tested for brucellosis by a simple blood test, especially if they were not tested for this infection shortly before the breeding was attempted and even more so if the males were not tested. Brucellosis is a serious and highly contagious sexually and orally transmitted canine disease. The infectious microorganism, Brucella canis, is shed in large numbers in semen, vaginal secretions and urine of infected dogs.
Other, more advanced diagnostic tools are abdominal radiographs (X-rays) and ultrasound to assess the integrity of internal reproductive organs; these can be particularly helpful to identify uterine infections (endrometritis, pyometritis). Vaginal swabs can be used to sample and examine vaginal cells microscopically through a process called cytology. Vaginal samples can also be submitted for culture, which is a process that attempts to grow any infectious microorganisms in a laboratory setting.
Various blood tests are available to measure the levels of circulating hormones that are critical to ovulation, conception, maintenance of pregnancy and successful delivery of a live litter. These include follicle stimulating hormone (FSH), luteinizing hormone (LH), estrogen, progesterone and thyroid hormones, among others. Progesterone assays are valuable to determine whether or not ovulation actually occurred. If an adult bitch has never gone through a heat cycle (primary anestrus), her actual chromosomal makeup can also be evaluated through a process called karyotyping.
More invasive advanced diagnostic techniques are surgical ultrasound-guided biopsies of the uterus and ovaries and vaginoscopy (looking into the vaginal canal using a wand-like instrument with a camera on its tip). Full surgical abdominal exploration under general anesthesia can also be done. Ovarian tumors and cysts can only be definitively diagnosed by exploratory abdominal surgery and biopsy; normally, a bitch with ovarian tumors will be spayed during that surgical diagnostic procedure. Biopsy samples will be submitted to a diagnostic laboratory for complete analysis.
Because the causes of infertility in female dogs are so widely varied, diagnosing the precise cause of the problem can be extremely difficult, time-consuming and costly. In the end, the reason for her infertility may never be determined.