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Basics ⬇

Basics

Overview

Inappropriate myometrial activity preterm, which can lead to abortion.

Signalment

Gravid female dog or cat, no age or breed predilection.

Signs

  • Early: no signs, fetal resorption evident ultrasonographically.
  • Late: vulvar discharge: hemorrhagic or lochial.
  • History of unexplained loss of pregnancy.

Causes & Risk Factors

  • Unknown; genetics can play a role; luteolysis can result; luteal insufficiency suspected but not documented.
  • Myometrial activity inappropriate for stage of pregnancy precedes luteolysis.

Diagnosis ⬆ ⬇

Diagnosis

Differential Diagnosis

  • Term gestation, onset of normal labor.
  • Pathologic loss of pregnancy (trauma, toxin, developmental disorder, or infectious causes).

CBC/Biochemistry/Urinalysis

  • Usually normal (typical anemia of pregnancy can be present).
  • Blood loss anemia, inflammatory leukogram can occur.

Other Laboratory Tests

Serum progesterone will be <2 ng/mL when abortion occurs.

Imaging

  • Ultrasonographic evaluation of fetal heart rate (stress evidenced by rates consistently <170).
  • Change in the normal morphologic appearance of uterus and fetuses when death occurs (See Web Figures 1, 2).

Diagnostic Procedures

  • Tocodynamometry is diagnostic: finding >0–2 contractions/hour is not normal for preterm (earlier than eighth week) gestation.
  • Quantitative (chemiluminescence, fluorescence enzyme immunoassay) progesterone assay is important to detect levels <2.0 ng/mL. Rapid in-hospital semi-quantitative assays are least accurate between 2 and 5 ng/mL.

Treatment ⬆ ⬇

Treatment

Medications ⬆ ⬇

Medications

Drug(s)

  • Tocolytics (terbutaline 0.03 mg/kg PO q6–12h PRN); the dose is titrated based on uterine monitoring.
  • ± Progestagen compounds: progesterone in oil dosed at 2 mg/kg IM q72h; altrenogest (Regu-Mate, Hoechst-Roussel), a synthetic progestagen manufactured for use in the mare, is dosed at 0.088 mg/kg PO q24h; oral progesterone (Prometrium® capsules) dosed at 10 mg/kg q24h with monitoring of serum progesterone q24–48h for dosage adjustments. Clients should be informed of potential side effects with exogenous progesterone, and should only be used if the serum progesterone is <2 ng/mL.

Contraindications/Possible Interactions

  • Prolonged gestation if terbutaline or progestagen compounds are not withdrawn 24–48 hours before due date calculated from first progesterone rise, luteinizing hormone peak, or Day 1 cytologic diestrus (see Breeding, Timing) if natural whelping is planned. If elective cesarean section is planned, medications can be continued until day of surgery.
  • Poor lactation if progestagen compounds are used (inhibits normal prolactin elevation resulting from declining progesterone level).
  • Masculinization of female fetuses if progestagen compounds are used.
  • Forced retention of a pathologic pregnancy if idiopathic premature labor is misdiagnosed.

Follow-Up ⬆ ⬇

Follow-Up

Miscellaneous ⬆

Miscellaneous

Usually a diagnosis by exclusion of all other causes of late-term abortion (Brucella canis, metritis, placentitis, trauma, metabolic disease, coagulopathy, inborn error of metabolism, genetic defects) prompting midterm tocodynamometry at the next pregnancy.

Internet Resources

http://www.ivis.org

Authors Autumn P. Davidson and Tomas W. Baker

Consulting Editor Sara K. Lyle

Suggested Reading

Concannon PW, McCann JP, Temple M. Biology and endocrinology of ovulation, pregnancy and parturition in the dog. J Reprod Fertil Suppl 1989, 39:3–25.

Davidson AP. Tocodynamometry detects preterm labor in the bitch prior to luteolysis. Proceedings, European Veterinary Society for Small Animal Reproduction, 2012, pp. 50–51.

Feldman EC, Davidson AP, Nelson RW, et al. Prostaglandin induction of abortion in pregnant bitches after misalliance. J Am Vet Med Assoc 1993; 202(11):1855–1858.

Johnson CA. High-risk pregnancy and hypoluteoidism in the bitch. Theriogenology 2008, 70:1424–1430.

Root Kustritz MV. Use of supplemental progesterone in management of canine pregnancy. In: Concannon PW, England G, Verstegen IIIJ, Linde-Forsberg C, eds., Recent Advances in Small Animal Reproduction. International Veterinary Information Service, Ithaca NY, www.ivis.org, 2001.

Scott-Moncrieff JC, Nelson RW, Bill RL, et al. Serum disposition of exogenous progesterone after intramuscular administration in bitches. Am J Vet Res 1990, 51:893–895.

Wilkens L. Masculinization of female fetuses due to the use of orally given progestins. J Am Med Assoc 1960, 172(10):1028–1032.