Render Unto Caesar: When to Medically Manage Dystocia & When to Proceed to Caesarian Section (C-Section)

The incidence of canine dystocia is difficult to assess as most normal deliveries go unrecorded; however, dystocia has been estimated to occur in 5-16% of whelpings. Incidence appears to be related to breed and litter size. Singleton or very large litters are more likely to be problematic. Brachycephalic breeds have a higher incidence as a result of physical attributes—large, blunt heads in relation to fetal body size and maternal pelvic diameter. Small and Toy breeds have an increased rate of dystocia because of body size, predisposition to eclampsia (hypocalcemia), and a propensity for small litters resulting in fetal oversize. Dystocia also has familial tendencies and nutritional associations.

Dystocias may be classified into two categories: Passive and Obstructive. Passive Dystocia is failure to engage or cessation of abdominal and uterine contractions—Uterine Inertia (UI). UI is the most common cause of dystocia. It can sometimes be managed medically, but often requires emergency C-section. Two types of UI are recognized. Primary UI is failure of the dam to progress to second stage labor (rupture of Chorio-allantoic membranes). Secondary UI is cessation of uterine contractions after the delivery of part of the litter. The physiologic explanation for UI is incompletely understood but is likely a combination of effects related to hormones and electrolyte concentrations. Calcium and magnesium, as evidenced in dairy cattle, play an active roll in uterine contraction and hence in UI. The positive response and return to labor after calcium supplementation in dogs further supports the role calcium plays in UI. It has been demonstrated that ionized calcium and total serum calcium concentrations, although within physiologically normal ranges, are significantly decreased in bitches in dystocia compared to eutocia. Similarly, prostaglandin and vasopressin are decreased in bitches diagnosed with uterine inertia, while oxytocin levels remain insignificantly different from eutocia bitches. Obstructive Dystocia is a physical impairment interfering with normal delivery (eg. fetal oversize or fetal malposition). Prolonged obstructive dystocia may result in secondary UI.  [...]