Parturition – When Things Go Wrong

Introduction

The term dystocia refers to an abnormal or difficult birth. Dystocia or difficult birth occurs in approximately 4% of Thoroughbred foalings. Abnormal orientation of the fetus in the birth canal (i.e. postural abnormalities) is the most common cause of dystocia in the horse. Dystocia is more common in mares during their first foaling (i.e. maiden mares) than in mares that have previously given birth to one or more foals. The ultimate goals in assisting in an equine dystocia are to save the life of the foal, save the life of the mare and to preserve the future fertility of the mare.

Time management during a dystocia

Active labour (Stage II) is a rapid event in most mares, with most foals delivered within 20–30 minutes after rupture of the chorioallantoic membrane. An owner or foaling attendant should be concerned if a foal has not been born or if significant progress towards birth has not occurred within 15–20 minutes after rupture of the outer chorioallantoic membrane and subsequent release of allantoic fluid (i.e. when a mare ‘breaks her water’).

Dystocia and foal survival

Dystocia in mares is a medical emergency and time is critical. It has been estimated that each 10 minutes increase in the duration of Stage II labour beyond 30 minutes is associated with a 10% increase in the existing risk of a foal being born dead and a 16% increase in risk of the foal not surviving to discharge from a referral hospital or clinic. Early detection of an equine dystocia and rapid appropriate intervention in problem cases are critical for foal survival. Placental separation and subsequent decrease in oxygen supply in utero are likely the primary factors that lead to fetal death during prolonged dystocia.

Dystocia management plan

It is strongly recommended that an emergency plan be formulated prior to the foaling season to prepare for a difficult birth, a medical problem with a newborn foal, or medical issues with the mare. The plan should be the result of a conversation among the mare owner, breeding farm/ranch manager, foaling attendant and the veterinarian(s). All personnel actively involved in foaling mares should be trained and ready to assist. A foaling kit should be readily available near the foaling stall. Management of a dystocia is dependent on training, experience and availability of farm personnel, as well as the proximity of veterinary services.

Early communication in the event of a dystocia

It is recommended that a foaling attendant call for assistance (on-farm personnel or veterinary assistance, as appropriate) in the following circumstances:

• If there has been no progress towards delivery after 15–20 minutes following rupture of the chorioallantois
• If progress towards delivery abruptly stops
• If the mare becomes acutely painful or exhibits signs of shock
• If the attendant is confident that a problem with foaling exists
• If the attendant is unsure if a problem with foaling exists
• If the attendant does not have the knowledge, training, or ability to identify or correct the problem.

Causes of dystocia in the mare

Mild dystocias are commonly managed on the breeding farm by foaling personnel. More complicated dystocias may require advanced training or experience and often require veterinary intervention. Failure of the fetus to be properly oriented in the birth canal as foaling progresses will almost always prevent normal passage and result in dystocia. The most common causes of dystocia in the mare are abnormalities of fetal posture (i.e. abnormal alignment of the head or forelimbs).

Initial physical examination of the mare during a dystocia

A brief physical examination should be performed to evaluate the health status of the mare. The examination should be performed in a large stall or other open area or in stocks that can be taken apart with removal of a few pins. It is not recommended to examine a pregnant mare experiencing a dystocia in solid- sided stocks, because many foaling mares will attempt to lie down during vaginal examination or fetal manipulation. Safety of personnel should be of paramount concern during all examinations and obstetrical procedures.

Intervention in an equine dystocia

Choices for relieving an equine dystocia include an assisted or controlled vaginal delivery, caesarean surgery or fetotomy. The final decision may depend on the status of the fetus, duration and severity of the dystocia, economic value of the mare and fetus, clinician expertise, client preference, facilities available and other considerations.

Assisted vaginal delivery

A reproductive examination is performed to identify the obstetrical problem, determine if the fetus is alive and to formulate a plan. The goals are to determine:

• If the chorioallantoic membrane had indeed ruptured
• Dilation status of the cervix
• Orientation of the fetus in the birth canal
• Live/dead status of the fetus
• If perineal, vaginal, cervical or other problems have already occurred.

A plan for intervention should be developed for each specific dystocia, based on the information above, the health status of the mare, duration of dystocia, economic value of the mare and foal and other factors. A backup plan should always be discussed in the event that the initial plan is not successful.

Foal care following a dystocia

Resuscitation equipment should be available on farms that foal a lot of mares and farm personnel should be trained in the proper care and use of the equipment.

Mare care following a dystocia

The reproductive tract of the mare should be examined for trauma that may lead to more severe medical issues and/or limit her future reproductive performance. It is common for the placenta to be retained following a dystocia.

Conclusion

Dystocia is a medical emergency and time is critical to optimise foal survival. The key factors in foal survival are early recognition of a foaling difficulty by breeding farm personnel and early appropriate intervention.

[...]