Canis ISSN: 2398-2942

Dystocia

Contributor(s): Kyle Braund, Autumn P Davidson

Introduction

  • Definition: difficulty delivering fetus(s) from the uterus through the birth canal (vagina, vestibule, vulva) normally resulting in birth.
  • Outcome: fetal and/or maternal morbidity and mortality, fading neonates, post-artum metritis.
  • Cause: fetal, maternal, combination.
  • Fetal:
    • Fetal abnormalities (hydrops fetalis, anasarca, hydrocephalic, twins).
    • Abnormal fetal position (fetal dorsum normally closest to dam dorsum; fetal ventrum closes to dam dorsum problematic) or posture (diving stance is normal, head elevation and shoulder flexion problematic).
    • Fetus exiting one horn and entering the other, blocking entrance into the uterine body.
    • 50% of canine fetuses are caudad (breech in humans) presentation, 50% cephalad, considered normal variation. Caudad can be problematic if pelvic limbs are in flexion.
  • Maternal:
    • Uterine inertia (primary Primary uterine inertia, secondary), herniation, adhesins, torsion, hydrops, lack of allantoic fluid, rupture.
    • Birth canal abnormalities: steep pelvic floor (brachycephalics), vaginal septum, stricture, vulvar edema.
  • Combination:
    • Mismatch between fetal size and birth canal dimensions (brachycephalics, chondrodystrophics, small litter size in breeds with litters typically >6 fetuses).
    • Singleton pregnancy: eventual fetal oversize +/- failure to initiate whelping (lack of fetal stress) causing prolonged gestation.
  • Treatment: depends on cause/type of dystocia. Supportive and specific (see below).
  • Prognosis: guarded to good.

Pathogenesis

Etiology

  • Maternal vs Fetal (see above); combination of maternal and fetal causes most common.

Pathophysiology

Deviation from normal labor

Stages of normal labor
  • First: uterine contractions increasing in frequency and duration. Normally 12-24 h in duration. Preceded by temperature drop to less than 99°F (37.2°C) accompanying luteolysis and progesterone decline to <2 ng/mL, occurring 12-24 h earlier.
Note: no external contractions of abdominal effort are visible in Stage 1.
  • Second: uterine contractions + abdominal efforts → neonatal delivery.
Note: uterine contractions are accompanied by visible external abdominal contractions in Stage 2.
  • Third: placental delivery (normally with fetus, can occur up to 24 h after).
    • Bitches normally transition from stage 2 to stage 3 until entire delivery is complete.

Diagnosis

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Treatment

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Gendler A, Brourman J, Graf K, Richards J, Mears E (2007) Canine dystocia: medical and surgical management. Compend Contin 29 (9), 551-62 VetMedResource.
  • Bergstrom A, Nodtvedt A N, Lagerstedt A S, Egenvall A (2006) Incidence and breed predilection for dystocia and risk factors for cesarean section in a Swedish population of insured dogs. Vet Surg 35 (8), 786-791 PubMed.
  • Davidson A P (2001) Uterine and fetal monitoring in the bitch. Vet Clin Small Anim Pract 31 (2), 305-313 PubMed.
  • Eneroth A, Linde-Forsberg C, Uhlhorn M & Hall M (1999) Radiographic pelvimetry for assessment of dystocia in bitches - a clinical study in two terrier breeds. JSAP 40 (6), 257-264 PubMed.
  • Darvelid A W & Lindeforsberg C (1994) Dystocia in the bitch - a retrospective study of 182 cases. JSAP 35 (8), 402-407 VetMedResource.


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