Parishmita Das¹, Hunmili Ronghangpi¹, Jini Ghosh¹, and Mohua Das Gupta^2*

Department of Animal Reproduction, Gynaecology and Obstetrics, College of Veterinary Science, AAU, Khanapara, Guwahati-781022

¹M.V.Sc scholar; ²Assistant Professor

*Corresponding author, Email: mohua.dgupta@gmail.com

Introduction

For most dog owners, the birth of a new litter is a moment of anticipation and joy. However, for some bitches, this natural event can become life-threatening due to a serious condition known as Uterine Inertia. It is one of the most frequent yet underdiagnosed causes of dystocia (difficult or obstructed labour) in dogs and can result in the death of both mother and pups if not promptly managed.

Uterine Inertia occurs when the uterus either fails to initiate contractions or cannot maintain them long enough to complete the birthing process. Despite being a frequent condition, it often goes unnoticed until it becomes an emergency.

Understanding the Uterus and Its Role in Labour

During normal whelping, two forces help expel the puppies:

1. Myometrial contractions (involuntary contractions of the uterus)
2. Abdominal straining (voluntary muscular effort)

Myometrial contractions are the first to act, pushing the foetus into the birth canal, which then stimulates abdominal muscles through reflexes to aid in expulsion. When uterine contractions are weak or absent, the abdominal muscles are not activated properly, leading to ineffective labour (Roberts,1971).

Types of Uterine Inertia: Primary vs. Secondary

Primary Uterine Inertia (PUI)

This is the most common form and is frequently observed in multiparous bitches (those that have had multiple pregnancies). It occurs when:

• The uterus never starts contracting (complete PUI), or
• It begins contracting but stops before delivering all the puppies (partial PUI).

Causes of Primary Uterine Inertia (Noakes et al., 2018)

1. Overdistension of the Uterus: Large litters or very big foetuses (common in breeds like Bulldogs or Pugs) stretch the uterus excessively, reducing its ability to contract.
2. Single Puppy Syndrome: A small litter (often just one or two pups) may fail to produce enough hormonal signals to initiate labour.
3. Hormonal Imbalance: Normal parturition depends on a precise balance between oestrogen and progesterone. High progesterone levels inhibit uterine activity, while a rise in oestrogen promotes it. Any disruption in this balance can prevent contractions.
4. Oxytocin or Prostaglandin Deficiency: When the foetus stretches and applies pressure on the cervix, the Ferguson reflex is triggered. This reflex stimulates the hypothalamus, specifically the paraventricular nucleus, to release oxytocin. Oxytocin then binds to its receptors on the smooth muscle cells of the myometrium, promoting uterine contractions. Additionally, oxytocin stimulates the production of prostaglandins, which aid in cervical dilation and enhance uterine muscle activity. A deficiency in either hormone can impair this process and myometrial contraction.
5. Hypocalcaemia (Low Blood Calcium): Calcium is crucial for muscle contractions, including those of the uterus. A deficiency can significantly reduce uterine contractility.
6. Fat Deposits in the Uterine Wall: Excess fat infiltration can reduce muscle tone and efficiency.

Clinical Signs of Primary Uterine Inertia

• Restlessness, panting, and nesting behaviour without active labour.
• Drop in rectal temperature (indicating impending labour) but no straining.
• Dilated cervix but no progress in delivery.
• Green vaginal discharge (uteroverdin) suggesting placental separation but no pup delivered.

Diagnosis

Diagnosis is based on:

• History (number of pregnancies, duration of labour signs).
• Clinical examination (abdominal palpation, vaginal inspection).
• Ultrasound to check for foetal movement and heartbeat, confirming viability.

Treatment of Primary Uterine Inertia

Veterinary intervention should be immediate and calculated:

1. Digital Vaginal Stimulation (Feathering): Can induce natural oxytocin release.
2. Fluid Therapy: Administering IV fluids like dextrose 5% DNS/ 0.9% saline helps to correct dehydration and restore energy.
3. Calcium Gluconate (IV): Corrects subclinical hypocalcaemia and strengthens uterine contractions @ 0.5-1.5 ml/kg body weight (Raut et al., 2009).
4. Oxytocin Injections: Carefully administered in low doses (0.5–5 IU IV), only when the uterus is not overfilled.
   • Important Note: Oxytocin should not be used if there is uterine over-distension as it may cause rupture (Uvnäs-Moberg, 2024).
5. Manual Assistance: Gentle traction if the birth canal is clear and the pup is accessible.
6. Caesarean Section: Indicated when medical management fails or if pups are at risk. Prompt surgery saves lives.

Secondary Uterine Inertia: When the Uterus Gives Up

Unlike primary inertia, secondary uterine inertia happens when the uterus becomes exhausted after prolonged or obstructed labour (Roberts,1971). The bitch may successfully deliver one or two pups but then stops due to muscular fatigue.

Causes Include (Magnus et al., 2023):

• Prolonged labour
• Foetal obstruction
• Partial cervical dilation
• Large or malformed puppies

Clinical Signs of Secondary Uterine Inertia

• Strong initial labour with delivery of one or two puppies.
• Sudden cessation of contractions.
• Remaining foetuses often become non-viable due to lack of oxygen.

Diagnosis and Treatment

• Similar diagnostic methods as PUI.
• If obstruction is ruled out, medical therapy (fluids, calcium, oxytocin) can be attempted.
• Caesarean section is the best option when labour does not resume, especially if live foetuses are present.

Prognosis: Guarded. Delay in treatment increases risks of foetal death, uterine rupture, infections, and metritis.

Preventive Measures for Breeders and Pet Owners (Jyothi and Gunaranjan, 2023)

• Regular prenatal check-ups.
• Nutritional support with calcium and energy supplements during late gestation.
• Monitoring for early signs of labour.
• Administration of oxytocin at home should never be attempted without veterinary supervision.

Conclusion:

Uterine Inertia is a condition that demands quick recognition and decisive action. Whether caused by hormonal imbalance, overdistension, or muscle exhaustion, the result is the same – interrupted birth with dire consequences if untreated.

Veterinarians play a crucial role in diagnosis, medical management, and surgical intervention. With growing awareness and timely care, both puppies and their mothers can be saved from the fatal grasp of this silent threat.

References:

Jyothi, K. and Gunaranjan, K.S. (2023). Management of primary uterine inertia in female dogs. Ind. J. Canine Pract. 15(2): 118-120.

Magnus, P.K.; Jayakumar, C.; Naicy, T.; Lali, F.A.; Hiron, M.H.; Abhilash, R.S. and Ajithkumar, S. (2023). Etiology behind canine uterine inertia: Role of uterine expression of MLCK4, MYH2 and PKC genes. Animal Reproduction Science. 256: 107298.

Noakes, D.E.; Parkinson, T.J. and England, G.C. (Eds.). (2018). Arthur’s Veterinary Reproduction and Obstetrics-E-Book: Arthur’s Veterinary Reproduction and Obstetrics-E-Book. Elsevier Health Sciences.

Raut, B.M.; Dhakate, M.S.; Upadhye, S.V.; Khan, L.A.; Khante, G.S.; Tiple, A.V. and Donekar, M.N. (2009). Uterine inertia in bitch. Veterinary World. 2(2): 71.

Roberts, S.J. (1971). Veterinary Obstetrics and Genital Diseases. Published by Author, Ithaca, NY, 2^nd edn. pp.227-235.

Uvnäs-Moberg, K. (2024). The physiology and pharmacology of oxytocin in labour and the peripartum period. American Journal of Obstetrics and Gynaecology. 230(3): S740-S758.

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