Dystocia, caesarean section, and foetotomy in the mare

Question 1

Incidence of dystocia

Answer 1

Occurs in about 4% of TB mares, higher in Shetlands and heavy horses
Higher in primiparous and very old mares
Most are fetal maldisposition

Question 2

Fetal maldisposition

Answer 2

Commonest reason for difficult foalings
Damage to uterine wall minimised by cupping sharp points of the deviated extremity while manipulating back into place

Question 3

Premature separation of the allantochorion

Answer 3

‘Red bag’
Rupture the sac and aid delivery quickly
Ensure not prolapsed bladder or vagina - look for cervical star

Question 4

Uterine inertia

Answer 4

Primary uterine inertia: voluntary suppression of parturition caused by disturbance, either leave alone or induce and monitor closely

Secondary uterine inertia: follows another primary cause of dystocia

Question 5

Weak abdominal contractions

Answer 5

Varying degrees
May be related to weakened musculature due to overstretching e.g. hydrops and twins, or some infirmity
May be no underlying cause

Foaling should be aided by controlled traction

Question 6

Failure to get down

Answer 6

Occasionally they foal standing up

Support the weight of the foal during delivery and for a few minutes after to prevent premature breaking of the cord

Question 7

Bony tissue obstruction of birth canal

Answer 7

Uncommon
May require c-section
Distortions of pelvic canal can follow pelvic fractures
Watch closely for indication of elective c-section

Question 8

Soft tissue obstruction of birth canal

Answer 8

Open Caslicks at start of 2nd stage labour (or as close to foaling as possible)
Vaginal obstruction uncommon
Cervix rarely a cause of dystocia unless previous damage

Question 9

Relative oversize of foal

Answer 9

Rare
When first foaling mares strain powerfully without adequate relaxation, there is a danger of recto-vaginal fistula formation

Question 10

Fetal monsters and abnormalities

Answer 10

Rare
Schistosomus reflexus is rare but one of the most common forms
Foetotomy useful

Question 11

Indications for c-section

Answer 11

The commonest reason for c/section in the mare is dystocia. Elective c/sections are carried out less frequently, but may be indicated for a variety of reasons including pelvic abnormalities, ventral abdominal rupture, or untreatable long bone fracture.

Question 12

Surgical approach to c-section

Answer 12

Most clinicians prefer the use of general anaesthesia for the operation as it is safer for the mare and allows a more controlled approach to the procedure.

Question 13

Post operative care after a c-section

Answer 13

If the placenta has been retained, oxytocin treatment is continued, and the mare’s uterus is manipulated per rectum on a daily basis to prevent adhesion formation. Postoperative intra-uterine lavage is carried out if there is evidence of or concern about endometritis. Parenteral antibiotic therapy should also be considered. The mare should be offered a light laxative diet and limited but regular exercise for the first few days. The foal is managed as deemed appropriate by its clinical status.

Question 14

Complications associated with c-section (mare)

Answer 14

Retention of placenta
Fatal haemorrhage
Peritonitis
Adhesions
Ventral oedema
Incisional herniation
Drying up subsequent to the box rest
Infertility may occur but rare

Question 15

Complications associated with c-section (foal)

Answer 15

Hypoxia
Effects of anaesthesia
Clamping of the cord and associated problems
Lack of compression which it would have received in birth canal

Question 16

Prognosis for c-section

Answer 16

Good for mare if the decision to operate is made early in dystocia and prolonged attempts at manual vaginal delivery haven’t been made. However, unless it was an elective operation, the foal is often likely to be dead at the start of surgery since survival during the second stage of labour is short

Question 17

What are the two techniques for a foetotomy

Answer 17

Percutaneous foetotomy: tubular fetotome through which a flexible wire saw is passed

Sub-cutaneous foetotomy: Involves dissecting parts of the fetus out within its skin

Question 18

Factors used to decide between fetotomy and c-section

Answer 18

Extent of foetotomy likely to be required
Accessibility of foetus
Experience of vet and availability of equipment
Future fertility of the mare (c-section if fertility is paramount)

Question 19

Moderate to mild asphyxia causes

Answer 19

• Maternal systemic disease
• Placental disease
• Foetal disease
• Intrapartum problems

Question 20

Chain of events following increased hypoxaemia and acidaemia

Answer 20

• Decrease pulmonary blood flow
• Decreasing left atrial return
• Dropping left atrial pressure
• Resulting in increasing right to left shunting through the foramen

Question 21

Early severe asphyxia results in:

Answer 21

• Stimulation of the foetus to breath while still in utero
• If gasping does not resolve asphyxia it will stop causing primary apnoea
• Then a second series of gasping (more irregular)
• Secondary apnoea, irreversible unless resuscitation is initiated
• May pass through these stages while still in utero