Contributors: Kyle Braund, Autumn P Davidson
Species: Canine | Classification: Diseases
Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading
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.
Breed Predisposition
- English Bulldog Bulldog.
- Boston Terrier Boston Terrier.
- Pug Pug.
- French Bulldog French Bulldog.
- Chihuahua Chihuahua.
Cost Considerations
- Varies based on medical vs surgical management, +/- emergency complications.
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.
- Second: uterine contractions + abdominal efforts → neonatal delivery.
- 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
Diagnostic Investigation
Clues to diagnosis/clinical signs
- Failure to initiate labor at term:
- Must confirm gestation length determination.
- Failure to proceed from stage 1 to stage 2, within 24 h.
- Failure to deliver all in timely manner (less than 8 h; 4-5 h ideal).
- Fetal or maternal distress:
- Fetal: cyanotic, difficult to resuscitate, stillborn.
- Maternal: hypotension, anemia, exhaustion, shock.
- Greater than 1 h stage 2 without delivery of neonate.
- Copious vaginal hemorrhage.
- Uteroverdin (green vulvar discharge indicating placental separation) without immediate delivery.
- Irreversible and unrecognized history of dystocia (vaginal strictures, uterine adhesions).
Tools to diagnose
- History (ovulation timing Ovulation detection), physical examination including vaginal examination Vaginal examination (digital or vaginoscopic Cystoscopy: transurethral cystoscopy -vaginoscopy):
- Term pregnancy is 56-58 days from diestrus day 1 or 66-64 days from the initial rise in progesterone Progesterone assay or the LH surge.
- Stat CBC Hematology: complete blood count (CBC), chemistries (BUN Blood biochemistry: urea, BG Blood biochemistry: glucose), electrolytes (iCa+ Blood biochemistry: ionized calcium), urine dipstick Urinalysis: dipstick analysis (ketones? Urinalysis: ketone).
- Radiography Radiography: abdomen (actually pregnant?, size and number of fetuses present? Fetal maturation (dentition visible?)
.
- Can indicate immediate surgical intervention rather than medical treatment (singleton).
- Can identify completion of labor when owner misinterprets litter size.
- Ultrasound Ultrasonography: uterus (viable, stressed?)
.
- Fetal HR should be >180-200 bpm.
- Degree of bradycardia reflects degree of fetal stress.
- Serial ultrasound permits evaluation of fetal response to medical therapy (bradycardia resulting from administration of calcium or oxytocin is a contraindication to further medial therapy).
- Can identify fetal abnormalities (anasarca).
- Can identify retained placentae.
- Fetal doppler:
- Permits evaluation of fetal heartrates, more technically challenging to find every fetus compared to ultrasound.
- Tocodynamometry (gold standard):
- Permits actual evaluation of myometrial activity:
- Frequency of contractions:
- Normal 1-12 contractions/hr.
- Strength of contractions:
- Normal 15-40+ mm Hg.
- Duration of contractions:
- 2-5 minutes.
- Frequency of contractions:
- Idenitifies abnormal activity (uterine torsion, rupture) indicating need for immediate Caesarean section.
- Permits actual evaluation of myometrial activity:
Treatment
Initial Symptomatic Treatment
- Initiate fluid support (5% dextrose in lactated Ringers).
- Correct any clinical pathology abnormalities identified (hypoglycemia, hypocalcmia, severe anemia).
Standard Treatment
Specific therapy
- Physical manipulation of obstructive dystocia difficult in the canine due to fetal fragility and small birth canals:
- Manipulation to reposition a fetus in the distal vaginal canal can be possible:
- Liberal use of lubrication (can pass through red rubber catheter at or cranial to the fetus).
- Avoid forceful traction or instrumentation.
- Gentle traction along path of vulva (towards the bitch's hocks) possible.
- Elevating the bitch's forequarters can help.
- Manipulation to reposition a fetus in the distal vaginal canal can be possible:
- Medical therapy as supported by clinical evaluation above:
- Calcium gluconate Calcium gluconate (administer first):
- Improves strength of myometrial contractions (delivery can occur with monotherapy).
- Serum iCa Blood biochemistry: ionized calcium levels are usually normal:
- 10% calcium gluconate 1 ml (0.465 mEq Ca+)/4.4 kg SC q 4-6h.
- Detectable response to administration of calcium despite eucalcemia:
- Intracellular mechanism of action.
- Oxytocin Oxytocin:
- Increases frequency of myometrial contractions.
- Oxytocin (administer second if needed):
- 10 U/mL 0.25-2.0 units per dam SC or IM q30-60 min.
- Excessive doses of oxytocin cause tetanic myometrial contractions and can promote uterine rupture and worsen fetal hypoxia.
- Calcium gluconate Calcium gluconate (administer first):
Surgical therapy: Caesarean section
- When medical therapy fails or is contraindicated:
- Fetal distress (worsening fetal bradycardia).
- Refractory inertia.
- When tocodynamometry shows an aberrant pattern or obstructive pattern.
- When maternal compromise is evident, after stabilization.
Outcomes
Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- O'Neill D G, O'Sullivan A M, Manson E A et al (2019) Canine dystocia in 50 UK first-opinion emergency care veterinary practices: clinical management and outcomes. Vet Rec 184, 409 PubMed.
- 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.