Uterine Inertia

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Introduction

Uterine inertia describes the failure of the uterus to expel a foetus normally and is a common cause of canine and feline dystocia.

Uterine inertia can be primary or secondary.

Primary Uterine Inertia

This describes the total or partial absence of contractions to expel a normal foetus through an unobstructed birth canal.

Several causes have been found:

Breed predisposition
Large litter overstretching the uterus
Small litter not stimulating the uterus enough. Small foetuses cannot apply enough pressure on the uterine wall and cervix to set up the Fergusson reflex.
Systemic disease: Obesity and lack of exercise, hypocalcaemia, septicaemia.

Complete primary uterine inertia occurs if 2nd stage labour does not begin. Partial inertia occurs if the 2nd stage begins but contractions soon fail.

Secondary Uterine Inertia

Uterine muscles become exhausted after prolonged contraction against an obstructing or oversized foetus or during birth of a large litter. There is usually subclinical hypocalcaemia and/or hypoglycaemia.

This can occur in the sow, bitch and guinea pig.

Diagnosis

Physical examination may help identify foetuses in the birth canal. Digital examination of the vagina will also enable the uterine and vaginal tone to be assessed.

Lack of a response to pressure per vaginum indicates a lack of the Ferguson reflex which indicates uterine intertia.

Radiography can be taken to assess the number and size of foetuses.

Ultrasound can help assess foetal viability.

Treatment

If the bitch is in good condition with normal sized puppies and no obstruction, medical treatment can be attempted.

Oxytocin can be administered intramuscularly, repeated at 30 minutes for a maximum of 3 injections.

Calcium gluconate or dextrose solution can also be administered if a suspicion of hypocalcaemia or hypoglycaemia exists.

A caesarean section is indicated if there is no response to the oxytocin, or if the foetuses are too large for a vaginal birth.


See also: Clinical Approach to Dystocia in the Dog and Cat


Uterine Inertia Learning Resources
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References

Pasquini, C. (1999) Tschauner's Guide to Small Animal Clinics Sudz Publishing

Slatter, D. (2002) Textbook of small animal surgery Elsevier Health Sciences

Noakes, D. (2001) Arthur's Veterinary Reproduction and Obstetrics Elsevier Health Sciences




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