Equine Obstetrics

Question 1

Average gestation length

Answer 1

335 to 342 days
• Tremendous variations from 305 to 400 with normal
foals born

Question 2

Physiological sources of variation

Answer 2

 Season of conception (Winter > Summer)
 Genetics/breed
 Fetal gender (Male > female)
 Hybrid (mule pregnancies)

Question 3

• Pathological factors altering gestation length

Answer 3

 Intrauterine growth retardation (nutrition, placental
abnormalities)
 Congenital hypothyroidism and other abnormalities
 Fescue toxicosis

Question 4

period of gestation associated with high risk foals

Answer 4

<320 days, high risk foals

Question 5

Signs of impeding foaling - mammary glands

Answer 5

• Mammary development:
Increase in size 1 month
before parturition
• Waxing 24 to 48 hours
before parturition

Question 6

Stage 1

Answer 6

• Positioning of the
fetus
• Yawing
• Colicky
• Sweating
• Rolling

Question 7

Stage 2: Fetal expulsion

Answer 7

• Passage of foal
through the cervix
into the birth canal
and rupture of the
chorioallantoic
membranes
• Follows immediately the
rupture of the
chorioallantoic
membranes. Powerful
expulsive abdominal
contractions
(Ferguson's reflex).
• Duration: 17 to 20 min.
(minimum 10 min. and
maximum 60 min.)

Question 8

Stage 3: Placental expulsion

Answer 8

• Placenta expelled inside
out
• Most mares deliver
placenta within 45 minutes
of foaling
• Retained placenta if fetal
membranes are not
expelled within 3 hours

Question 9

predisposing factors to premature placental separation

Answer 9

• Predisposing factors
• Placentitis
• Fescue toxicosis
• Make sure it the
chorioallantois

Question 10

Equine obstetrics - options

Answer 10

• Assisted Vaginal Delivery
(AVD)
• Controlled Vaginal Delivery
(CVD)
• Fetotomy
• Cesarean section

Question 11

Approach: Standing manipulation

Answer 11

• Sedation
 Xylazine (0.6-0.8 mg/kg) +
butorphanol (0.025- 0.01 mg/kg)
 Detomidine (0.01-0.02 mg/kg) +
butorphanol
• Caudal epidural (5-8 ml of
lidocaine 2%)
• Uterorelaxant
 Clenbuterol (0.3-0.5 mg total IV)
 Buscopan (0.3 mg/kg IV)
• Good for AVD
• Ideal for large breeds
• Ideal for fetotomy

Question 12

Common postural abnormalities resolved by AVD

Answer 12

• Foot nape
 High risk for 3rd degree
rectovaginal tears
• Lateral head and neck deviation
• Carpal flexion

Question 13

Controlled Vaginal Delivery protocol

Answer 13

• General anesthesia
• Hoist
• Ideal of CVD and if Csection
may be considered
• Manipulation should be kept
to a maximum of 15 minutes

Question 14

indications for CVD

Answer 14

 Shoulder flexion
 Ventral deviation of the head
and neck
 Hock flexion
 Unilateral and bilateral hip
flexion

Question 15

Approach: Fetotomy

Answer 15

Approach: Fetotomy
Ideally in standing position
1. Attempt only if one has experience with technique
2. Birth canal is wide enough and fetus is easily
accessible and does not show severe abnormalities
3. Provide heavy sedation and caudal epidural anesthesia
4. Provide ample lubrication and give clear instruction to
assistant
5. Well-planed cuts based on determination of the position
and posture of the fetus. Partial fetotomy (2 or less cuts)
preferred
6. Supportive therapy intravenous fluids, broad spectrum
antimicrobials, pain management, NSAIDs

Question 16

General care post-dystocia

Answer 16

• Foal
• Resuscitation and routine foal care
• Check for broken ribs
• Mare (see details in “postpartum disorders”)
• Defecation (fecal softener, mash, mineral oil)
• Urination
• Pain management
• Uterine lavage
• Tetanus prevention
• Monitor temperature daily for at least 3 days
• Monitor digital pulse

Question 17

Life-threatening complications of dystocia

Answer 17

 Retained placenta
 Toxic metritis
 Peritonitis
 Urinary bladder rupture/eversion
 Uterine laceration or hemorrhage
 Uterine prolapse
 Rectal prolapse
 Rectal tears

Question 18

Non life threatening complications of dystocia

Answer 18

Non-life-threatening
 Cervical lacerations
 Recto-vaginal tears
 Vaginal laceration, adhesions
 Mastitis