Maternal Metabolic and Endocrine Disorders That Can Compromise Canine Pregnancy

Maternal health has a direct bearing on pregnancy progression and neonatal viability. Among the conditions that require particular attention are pregnancy toxemia, gestational diabetes mellitus, hypoluteoidism and hypothyroidism. These disorders can present differently, but each can affect the pregnancy, the timing or safety of delivery, and the condition of the puppies. 

Pregnancy Toxemia: Pay Attention to Late-Pregnancy Anorexia 

Canine pregnancy toxemia is primarily associated with late pregnancy and is characterized by hypoglycemia, ketosis, ketonuria, and liver lipidosis. Initial weakness may progress to seizures, collapse, and, in severe cases, death¹. Bitches carrying large litters are at increased risk, particularly when anorexia occurs during the final two weeks of pregnancy².

Diagnosis is based on the clinical presentation, together with hypoglycemia and increased ketone bodies in blood and urine. Glucose supplementation forms part of treatment^1,2,3.

For a bitch in late pregnancy, therefore, a noticeable reduction in food intake should not be dismissed, particularly when the litter is large. Assessment of blood glucose and ketone concentrations can help identify metabolic compromise. 

Gestational Diabetes May Have Few Obvious Signs 

Gestational diabetes mellitus (GDM) can develop without typical clinical signs. Pregnancy itself is associated with increased insulin resistance, with progesterone and growth hormone contributing to insulin resistance and carbohydrate intolerance^2,4.

Persistent hyperglycemia accompanied by glucosuria, interpreted alongside the history and clinical findings, supports the diagnosis of GDM. Once GDM is identified, fetal viability should be assessed regularly using ultrasound. Fetal size and viability can influence decisions regarding the timing of cesarean section. Delivering too early may increase the risk of premature birth, while delaying intervention when fetal distress develops may have serious consequences^2,4,5.

Puppies from affected pregnancies may also be more likely to develop hypoglycemia, hyperbilirubinemia, hypocalcemia, and poor suckling. Management may require intensive fluid and insulin therapy to correct water, electrolyte, acid-base, and glucose abnormalities².

Interpreting Progesterone in Suspected Hypoluteoidism 

Hypoluteoidism refers to insufficient progesterone production and secretion by the corpus luteum². Progesterone is necessary for pregnancy maintenance. A serum concentration of at least 2 ng/mL has been considered important for maintaining pregnancy^2,6, although miscarriage has also been reported with concentrations below 10 ng/mL².

Progesterone results require careful interpretation because different testing methods and devices can produce different values. The assay method should always be considered when interpreting the result⁷.

A falling progesterone concentration should not automatically be interpreted as the primary cause of fetal loss. Fetal distress, abortion, infectious agents, maternal health problems, trauma and poor nutrition can also contribute to declining progesterone concentrations [34,45,46]. Diagnosis of primary corpus luteum insufficiency therefore requires evidence of a gradual progesterone decline together with assessment of fetal viability.

Hypothyroidism Can Affect Reproductive and Neonatal Outcomes 

Untreated hypothyroidism has been associated with reduced fertility, variable interestrus intervals, abortion, and stillbirth. It may also predispose the bitch to dystocia because of prolonged labor and reduced contraction intensity. Puppies have been reported to have higher rates of low birth weight, low viability, and overall litter mortality².

Levothyroxine supplementation was associated with reversal of the negative effects of hormone deprivation on neonatal birth weight and mortality⁸. However, thyroid hormone changes during pregnancy and whether supplementation requirements should be adjusted as pregnancy progresses remain areas of uncertainty^2,9.

Key Takeaways 

• Treat late-pregnancy anorexia as an important warning sign, particularly in bitches carrying large litters.

• Evaluate glucose and ketone concentrations when pregnancy toxemia is suspected.

• GDM may occur without obvious clinical signs; persistent hyperglycemia with glucosuria supports diagnosis.

• In GDM, combine maternal metabolic assessment with regular fetal viability monitoring.

• Interpret progesterone according to the assay method and testing device used.

• A declining progesterone concentration should be evaluated alongside fetal viability rather than automatically attributed to primary hypoluteoidism.

• Untreated hypothyroidism may be associated with reduced fertility, dystocia, low birth weight, reduced neonatal viability and increased litter mortality.

For the practicing veterinarian, recognizing maternal metabolic and endocrine abnormalities early allows closer assessment of both the bitch and her litter. The clinical picture, laboratory findings and fetal status should be considered together when deciding how the pregnancy should be monitored and managed. 

References 

1. Nak D, Nak Y, Shahzad AH. Pregnancy toxemia in a golden retriever bitch, a case report. Adv. Anim. Vet. Sci. 2020;8(11):1184-7. https://researcherslinks.com/table_contents_detail/Advances-in-Animal-and-Veterinary-Sciences/33/1543/html 

2. Uchańska O, Ochota M, Eberhardt M, Niżański W. Dead or alive? A review of perinatal factors that determine canine neonatal viability. Animals. 2022 May 30;12(11):1402. https://www.mdpi.com/2076-2615/12/11/1402 

3. Frehner BL, Reichler IM, Keller S, Goericke‐Pesch S, Balogh O. Blood calcium, glucose and haematology profiles of parturient bitches diagnosed with uterine inertia or obstructive dystocia. Reproduction in Domestic Animals. 2018 Jun;53(3):680-7. https://www.academia.edu/download/116388773/rda.1315720240626-1-oscepj.pdf 

4. Nelson RW, Reusch CE. Animal models of disease: classification and etiology of diabetes in dogs and cats. Journal of endocrinology. 2014 Sep 1;222(3):T1-9. https://scholar.archive.org/work/xphn6jw6wnbxrjjkje23wjfsri/access/wayback/https://joe.bioscientifica.com/downloadpdf/journals/joe/222/3/T1.pdf 

5. Fall T, Johansson Kreuger S, Juberget Å, Bergström A, Hedhammar Å. Gestational diabetes mellitus in 13 dogs. Journal of veterinary internal medicine. 2008 Nov;22(6):1296-300. https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1939-1676.2008.0199.x 

6. Hinderer J, Lüdeke J, Riege L, Haimerl P, Bartel A, Kohn B, Weber C, Müller E, Arlt SP. Progesterone concentrations during canine pregnancy. Animals. 2021 Nov 24;11(12):3369. https://www.mdpi.com/2076-2615/11/12/3369 

7. Hussein HA, Schuler G, Conze T, Wehrend A. Comparison of three progesterone quantification methods using blood samples drawn from bitches during the periovulatory phase. Veterinary World. 2022 Jan 24;15(1):119. https://pmc.ncbi.nlm.nih.gov/articles/PMC8924395/pdf/Vetworld-15-119.pdf 

8. Panciera DL, Purswell BJ, Kolster KA, Werre SR, Trout SW. Reproductive effects of prolonged experimentally induced hypothyroidism in bitches. Journal of Veterinary Internal Medicine. 2012 Mar;26(2):326-33. https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/j.1939-1676.2011.00872.x 

9. Cecere J, Purswell B, Panciera D. Levothyroxine supplementation in hypothyroid bitches during pregnancy. Theriogenology. 2020 Jan 15;142:48-53. https://vtechworks.lib.vt.edu/bitstreams/be761614-4b51-46df-83c0-c33d48fce008/download