Review details metabolic and endocrine dysregulation in complicated canine pregnancy and parturition outcomes

Complicated pregnancy and parturition pose significant risks to both mother and offspring in dogs, with complications affecting 5-37% of all canine whelpings. Current understanding of the underlying pathophysiology for many conditions, such as gestational diabetes mellitus, pregnancy toxemia, hypocalcemia, and luteal insufficiency, remains incomplete. Specifically, primary uterine inertia (PUI), the most common type of dystocia, lacks clear, universally applicable conclusions regarding its multifactorial origin, hindering effective clinical management and necessitating a deeper dive into its endocrine and molecular drivers.

This review systematically discusses metabolic, endocrine, and molecular dysregulation underlying canine pregnancy and parturition complications within a clinical context. It synthesizes existing literature on conditions like gestational diabetes mellitus, pregnancy toxemia, hypocalcemia, luteal insufficiency, and hypothyroidism, all linked to negative maternal and fetal outcomes. The analysis also covers the infrequent but severe gestational pseudo-Addisonian crisis and recent advances in understanding primary uterine inertia (PUI), identifying gaps in current pathophysiological knowledge.

The review highlights several metabolic and hormonal abnormalities contributing to complicated canine pregnancies. These include gestational diabetes mellitus, pregnancy toxemia, hypocalcemia, luteal insufficiency, and hypothyroidism, all associated with adverse maternal and fetal outcomes. A rare but severe complication, gestational pseudo-Addisonian crisis, is also discussed, noting its yet unexplained pathophysiology. For primary uterine inertia (PUI), the most frequent dystocia, a multifactorial origin is supported, though definitive conclusions remain elusive. Potential factors implicated in PUI development include lower than normal maternal peripheral oxytocin and blood ionized calcium concentrations. Furthermore, placental dysfunction leading to decreased prostaglandin F2α production may be involved. The review also links PUI to changes in the expression of several contractility-associated genes and proteins in the uterus, which could alter uterine contractility or reflect the time-dependent progression of labor. Future studies are urged to focus on the interplay between the placenta, uterus, and cervix to elucidate the mechanical, endocrine, and molecular mechanisms of PUI.

Complications during parturition affect a significant 5-37% of all canine whelpings, underscoring the clinical importance of understanding these dysregulations.