Uterine Inertia

Note: We do not currently have a health liaison for this disorder. If you would like to volunteer, please contact president@samoyedhealthfoundation.org and we will be happy to answer any of your questions. For a description of the position, please click on disorder health information liaison.

Thank you to Hazel Fitzgibbon for providing this disorder information.

Summary

Uterine Inertia is the failure of contractions during whelping. Normally the bitch strains and muscles contract pushing puppies into the birth canal and then expelling them.

Uterine Inertia can fall into two categories. “Primary Inertia” occurs in heavily pregnant bitches near their whelping date. The bitch fails to have contractions, but the cervix dilates and the placentas can detach from the uterine wall.

![mom and pups2](/img/mom_and_pups.jpg)

‘Inertia,’ or ‘secondary inertia,’ is when the bitch stops contractions part way through a whelping, and is one of the most frequent causes of Dystocia (abnormal or difficult birth). It can be the result of uterine fatigue from a puppy blocking the birth canal which the bitch has failed to expel.

Signs and Symptoms

Primary Inertia is a difficult condition to detect it you do not know to watch for it. Often you will only notice that the bitch is uncomfortable. This is when having good records of when the bitch has been mated are necessary. If you have had hormone tests for ovulation, this also helps in determining if she is overdue. The main physical sign is when dark green liquid (placental fluid) appears and the bitch is not having contractions. She may also be in pain. More advanced cases show pale mucus membranes and shock.

Inertia happens after a whelping has started. The rule of thumb is no more than an hour between puppies, however this has been found to be incorrect in practice by many breeders with several hours being experienced by some, especially if the bitch goes to sleep! This is when you need to know if there are more puppies to get out.

Causes

Primary Inertia has a couple of causes. The main one is a lack of the hormone which starts the contraction process. A second one is the size of the litter; a bitch carrying a huge litter can be so extended that the muscles are already stretched to the limit and there is no room for contractions. Inertia also has more than one cause. A mis-presented puppy can cause a bitch to contract with the result that the bitch is too tired to continue. A big litter can leave the bitch exhausted and she may need help to continue.

Risk Factors

Small, one to two pup, litter size (leading to insufficient hormonal stimulation to initiate labor)
Very large litter size (uterus “overstretched')
Overweight dam
Poor muscle tone in dam due to age or other factors
Prior history of uterine inertia

Diagnostic Tests

A thorough physical exam should be given by the vet. For primary inertia he will be able to tell if the cervix is dilated and act accordingly.

For inertia during whelping, the vet should be able to feel if there is a puppy blocking the birth canal. An x-ray may be used to see if there are more puppies awaiting birth. Fetal monitoring of the unborn puppies heart rates can assist in determining if they are under excessive stress.

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

In primary inertia, a caesarean section as soon as possible is the only way to ensure any puppies survive. The puppies will drown if it is performed too late. If a caesarean is not performed in time, the puppies will die and the bitch will likely die from the resulting infection.

For inertia after whelping has started, Oxytocin and Calcium injections can be tried to restart contractions if the bitch is showing no other physical signs, although when to use these is somewhat controversial (see links). If there is bleeding, a caesarean is required. If there is a puppy blocking the birth canal, the vet may be able to manually reposition it and deliver it normally, but the rest of the litter could be at risk if normal contractions do not start again. More often than not, a Caesarean has to be performed.

Management

The owner should consult with their veterinarian prior to breeding a female who has had primary uterine inertia, so the owner fully understands the risk factors involved in a re-breeding of that female. Likewise, the owner should consult with their veterinarian about the risk factors for more than 2 C-sections on a bitch, due to resultant scarring on the uterine horns.

But “A bitch that has had surgical inseminations is not more prone to needing a caesarean section nor having whelping difficulties^1^” so there should be no more reason to have inertia after AI than for any other bitch.

[AKC Vet Outreach news ] ![2 bones](/img/2-bones.gif)

References

S. Romagnoli, F. F. de Souza, A. Rota, I. Vannozzi (2004) Prolonged interval between parturition of normal live pups in a bitch. Journal of Small Animal Practice 45 (5), 249–253.
Dystocia in small animals. In the online Merck Veterinary Manual.
Transcript: Canine Reproduction Seminar with Dr. Robert Van Hutchison. Tuesday, January 08, 2002 from the veterinarypartner.com website – Lots of good information relating to whelping and pregnancy in this online seminar
Handbook of Veterinary Obstetrics, 2nd edition, 2004 By Peter G. G. Jackson Textabook