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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Fetoplacental unit cannot meet fetal demands.
  • Intrauterine growth retardation, malnutrition, prolonged gestation, preterm delivery, pregnancy loss

Pathophysiology

  • Physical constrictions—body pregnancy; intraluminal adhesions, endometrial cysts, lymphatic stasis, endometrial fibrosis, glandular degeneration (endometrosis).
  • Placentitis—disruption of microcotyledonary attachments.
  • Histiotroph—nutrient exchange prior to placental formation, continues between microcotyledonary attachments.
    • Increased during pregnancy.
    • Production depends on endometrial gland competence, density

Systems Affected

Reproductive

Signalment!!navigator!!

  • Aged; multiparous.
  • History of endometritis, reproductive failure.
  • Twin pregnancy

Signs!!navigator!!

General Comments

  • Preterm delivery.
  • Prolonged gestation, term delivery of fetus inappropriate for gestational age. Dysmaturity—underweight, silky haircoat, erupted incisors, major organ dysfunction, sepsis. Post maturity—elongated hair coat, appropriate skeletal formation, decreased muscle mass

Historical Findings

  • Previous episode.
  • Endometrial biopsy—loss of epithelial layer, fibrosis, glandular nesting, decreased gland number

Physical Examination Findings

  • Uterus—intraluminal adhesions; segmental aplasia; cystic structures.
  • Placenta—localized or generalized poorly villous chorionic surface, pale appearance

Causes and Risk Factors!!navigator!!

  • Placentitis.
  • Degenerative endometrial change.
  • Age.
  • Increased parity.
  • Chronic endometritis.
  • Poor vulvar conformation.
  • Uterine infection

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Infectious abortion.
  • Noninfectious abortion—systemic illness, uterine torsion, developmental anomalies, umbilical pathology, spontaneous fetal death.
  • Prolonged gestation—fescue toxicosis; fetal endocrine abnormalities.
  • Fetal malnutrition—maternal disease

CBC/Biochemistry/Urinalysis!!navigator!!

  • Systemic pathology, if any.
  • No changes directly attributable to placental insufficiency

Imaging!!navigator!!

Transabdominal US

  • Placental detachment.
  • Intrauterine growth retardation—more pronounced later in gestation.
  • Asymmetrical development—disproportionate; little body fat or muscle

Transrectal US

Cervical placenta—thickness, detachment.

Pathologic Findings!!navigator!!

Gross

  • Placenta—avillous areas.
  • Small placenta—normal 11% foal birth weight (Thoroughbred).
  • Multiple pregnancies—placental apposition prevents endometrial attachment, nutrient/gas/waste exchange.
    • Abortion of both fetuses, or 1 dead and/or mummified.
    • If pregnancy reaches term, remaining twin small for gestational age.
  • Placentitis, detachment, exudate

Histopathologic

  • Placenta—reduced microcotyledon formation.
  • Endometrial biopsy—fibrosis, glandular nesting, reduced endometrial glands, lymphatic stasis, varying inflammation

Treatment ⬆ ⬇

TREATMENT

  • Placental insufficiency—postpartum diagnosis suggested by neonatal and placental appearance.
  • Prepartum—oxygen supplementation in an effort to raise fetal oxygen.
  • Manage inflammatory/infectious conditions affecting placenta

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Contraindications/Possible Interactions!!navigator!!

Establish fetal viability before treating—transabdominal US; fetal heart rate.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • US.
  • Fetus—viability, fetal heart rate.
  • Placenta—thickness, detachment

Prevention/Avoidance!!navigator!!

  • Detect/repair anatomic defects—vulvar conformation, cervical competence.
  • Endometrial biopsy—evaluate density of endometrial glands, inflammation (acute—neutrophilia; chronic—plasmacytic, lymphocytic), degenerative changes (periglandular fibrosis, diffuse; lymphatic, dilation, stasis).
  • Endometrial cytology—eosinophilia; association with pneumovagina.
  • Early detection—placental thickness, areas of detachment

Possible Complications!!navigator!!

  • Abortion.
  • Undersized, weak neonate.
  • Premature placental separation

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

  • Perinatal asphyxia.
  • Placentitis.
  • Premature placental separation.
  • Sepsis

Age-Related Factors!!navigator!!

Endometrial competence declines with increasing age, parity.

Pregnancy/Fertility/Breeding!!navigator!!

Abortion

Abbreviations!!navigator!!

US = ultrasonography, ultrasound

Suggested Reading ⬆ ⬇

Bracher V, Mathias S, Allen WR. Influence of chronic degenerative endometritis (endometriosis) on placental development in the mare. Equine Vet J 1996;28(3):180–188.

Bucca S, Fogarty U, Collins A, Small V. Assessment of feto-placental well-being in the mare from mid-gestation to term: transrectal and transabdominal ultrasonographic features. Theriogenology2005;64:542–557.

Giles RC, Donahue JM, Hong CB, et al. Causes of abortion, stillbirth, and perinatal death in horses: 3,527 cases (1986–1991). J Am Vet Med Assoc 1993;203:1170–1175.

Pozor M. Equine placenta—a clinician's perspective. Part 2: abnormalities. Equine Vet Educ 2016;28:396–404.

Wilsher S, Allen WR. The effects of maternal age and parity on placental and fetal development in the mare. Equine Vet J 2003;35:476–483.

Author(s) ⬆

Author: Peter R. Morresey

Consulting Editor: Carla L. Carleton