Contributors: Autumn P Davidson, Carlos Pinto, Angelika von Heimendahl

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Deviation from anticipated, typical estrous cycle events in a bitch intended for breeding can prompt presentation to a veterinarian for evaluation.
  • Considerable physiological variation may occur within the normal canine reproductive cycle, breeders commonly interpret such variation as an indication that an abnormality exists. The clinician must differentiate bitches having normal estrous cycles with unexpected patterns from those with true abnormalities. Detection of individual variation within the normal range of events in a fertile bitch can be crucial to providing effective counseling concerning breeding management. Additionally, evaluation of the estrous cycle for actual abnormalities is an important component in assessing the apparently infertile bitch. Variations from normal estrous cycle events in the bitch can sometimes be traced to specific ovarian or uterine disorders. Frequently, infertility results from inadequate timing of breeding in relation to optimal fertile time of the bitch.

Presenting Signs

  • Non gravid uterus or evidence of complete resorption of conceptus at the normal time of pregnancy evaluation (25-30 days post LH surge) Pregnancy: diagnosis.

Acute Presentation

  • Same.
  • Differentiate from other causes of failure to reproduce: abortion Abortion / stillbirth , dystocia Dystocia , stillbirths, poor maternal instincts, neonatal mortality.

Geographic Incidence

  • None.

Age Predisposition

  • Smaller litter size and increased neonatal mortality associated with advancing age in the bitch for undetermined reasons, but likely associated with expected deterioration of uterine health (uterine pathology such as cystic endometrial hyperplasia Pyometra , etc).

Breed Predisposition

  • Purebred animals in general may present with lower fertility than mixed breeds or mongrel dogs.
  • Inbred individuals are more at risk.

Public Health Considerations

Cost Considerations

  • Moderate to significant investment necessary to evaluate failure to conceive.

Special Risks

  • Undetermined invasiveness of uterine and ovarian biopsies.



Predisposing Factors

  • Irregular or atypical proestrus or estrus.
  • Irregular or atypical interestrus intervals.
  • Husbandry problems.
  • Male inherent infertility (oligospermia, asthenospermia or teratospermia; often all three present).
  • Malnutrition; poor body condition.
  • Iatrogenic.
  • Endocrinopathies (disorders of the thyroid gland).
  • Age.
  • Genetic.


  • Silent heat, split heat, shorter or longer than anticipated parts of the estrous cycle; relatively long interestrus intervals (>10 months); relatively short interestrus intervals (</=4 months).
  • Prolonged proestrus/estrus Prolonged pro-estrus and estrus.
  • Bred outside of the fertile window (most common cause of infertility in the UK), improper breeding technique.
  • Subfertile male, infertile male, inadequate use of chilled or frozen semen.
  • Inadequate plane of nutrition.
  • Metabolic disease.
  • Administration of abortifacients, hormones.
  • Hypothyroidism Hypothyroidism , hyperadrenocorticism Hyperadrenocorticism , disorders of the hypothalamic pituitary ovarian axis.
  • Uterine pathology.


  • Uterine pathology: repeated exposure to estrogen and progesterone predictably results in cystic endometrial hyperplasia which may or may not be associated with other uterine disorders (hydrometra, mucometra, pyometra Pyometra ).
  • Ovarian follicular cysts: prolonged proestrus or estrus, anovulation.
  • Ovarian luteal cysts: prolonged diestrus, increased risk of cystic endometrial hyperplasia.
  • Non functional ovarian parenchymal cysts suppress normal cycling.
  • Immune mediated oophoritis (rare).
  • Premature ovarian senescence (rare).


  • Evaluation of the ovarian cycle must take place during the estrous cycle. Average interestrus interval (diestrus and anestrous) is 7 months; the average proestrus and estrus are 9 days each, average diestrus is 45-70 days.


  • Screen every breeding dog forBrucella canis.


Presenting Problems

  • History of failure to reproduce based on the owners belief that conception did not occur.

Client History

  • Failure to conceive based on belief that good breeding strategies took place and pregnancy failed to occur.

Clinical Signs

  • Usually none other than non-gravid state.
  • Signs of estrous cycle depend on time of presentation (anestrus, proestrus, estrus, and diestrus).

Diagnostic Investigation

  • Thorough history of bitch health, diet, medications and supplements, onset and regularity of cycles, breeding history including details about identification of fertile window (if any), type of breeding (natural with tie, artificial insemination, etc if known) and details confirming male fertility (if documented).
  • History of method of pregnancy diagnosis conclusion of infertility is based on.
  • Physical examination including specific evaluation of reproductive organs.
  • CBC, chemistry panel, urinalysis/culture if indicated. Further endocrinologic testing as indicated (thyroid panel).
  • Brucella canisscreen.
  • Documentation of bitch estrous cycle parameters via serial vaginal cytology and serial progesterones.
  • Ultrasound of the abdomen and specifically the reproductive tract Ultrasonography: ovary Ultrasonography: uterus.
  • Breeding soundness evaluation of the male intended for the next breeding attempt if indicated (not proven to be fertile recently) Breeding soundness examination.
  • Vaginoscopy Vaginal examination Cystoscopy: transurethral cystoscopy/vaginoscopy.
  • Rarely, karyotyping.

Histopathology Findings

  • Rarely, uterine biopsy is indicated prognostically (diagnoses of CEH in the UK done by ultrasound not biopsy). Evidence of cystic endometrial hyperplasia warrants a poor prognosis for fertility.
  • Retrospectively, it is very important to perform histopathology of the ovaries and uterus if the bitch is ovariohysterectomized Ovariohysterectomy to confirm the diagnosis.

Differential Diagnosis

  • Husbandry problems.
  • Male subfertility or infertility.
  • Brucella canis.
  • Cystic endometrial hyperplasia/hydrometra/mucometra/pyometra complex Pyometra.
  • Hypothyroidism (not documented in veterinary literature; irregular cycles, increased pregnancy loss documented in hypothyroid women).
  • Disorders of sex development Disorders of sexual development.
  • Iatrogenic causes: birth control, corticosteroids, holistic/herbal remedies.
  • Anatomic problems precluding natural breeding (vaginal structures).


Initial Symptomatic Treatment

  • Treat any clinical pathologic abnormalities detected: eg urinary tract infection, hypothyroidism, metritis/pyometra.
  • Optimize nutrition.
  • Stop unnecessary or potentially problematic drugs (corticosteroids, holistics, herbal remedies).
  • Repair vaginal anomalies (strictures) or perform artificial insemination Artificial insemination: surgical Artificial insemination: non-surgical.
    In the UK AI only permitted by Kennel Club if several regulations are not breached, also may need c-section because of stricture not considered ethical in the UK.

Standard Treatment

  • Unilateral follicular ovarian cysts and unilateral luteal cysts can be treated by ipsilateral ovariectomy.
  • Short interestrus intervals may be treated with mibolerone (reproductively safe).


  • Ovulation timing based on serial determinations of concentrations of serum progesterone and LH Progesterone assay.
  • Pregnancy evaluation by ultrasonography beginning at 25 days post LH (frequently the LH surge is only inferred from progesterone hormonal profiles).

Subsequent Management


  • Confirm male fertility with other bitches under similar management.


  • Monitor cycle and consider breeding with an alternative fertile male.
  • Consider intrauterine insemination via trans cervical endoscopy to rule out cervical semen penetration problems.
  • Advise to breed bitches without skipping cycles (not allowed in UK where bitches should only have one litter/year) if pregnancy achieved and multiple litters desired.



  • Good unless ovarian or uterine pathology is present.

Expected Response to Treatment

  • 80% favorable due to correctable breeding management and use of fertile male.

Reasons for Treatment Failure

  • 20% true infertility secondary to ovarian or uterine pathology.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Wilborn R R, Maxwell H S (2012) Clinical approaches to infertility in the bitch. Vet Clin North Am Small Anim Pract 42 (3), 457-468 PubMed.
  • Johnston S D, Olson P N, Root M V (1994) Clinical approach to infertility in the bitch. Semin Vet Med Surg (Small Anim) (1), 2-6 PubMed.

Other sources of information

Other Sources of Information