Chapter 5 Eutocia and Dystocia in the Dog

 

 

 

 5.1 Endocrinological changes observed shortly before parturition

• 1. Exact mechanisms of parturition in the dog is not known: pieces of information are extrapolated from human and other species.
• 2. Approximately 24-48 hours prior to parturition, serum progesterone decreases; a decrease to 2 ng/ml had been recorder.
• 3. Increased serum corticosteroids: may be inconsistent and may not be proportional to decreased serum progesterone levels.
• 4. Increased serum prolactin levels: this is often seen shortly after the decrease in serum progesterone levels precipitates the prolactin release. This explains why some non-pregnant bitches spayed during diestrus may lactate shortly after the surgery.
• 5. Serum estrogen levels may be elevated in several species however this has not been fully established in the dog. 

5.2 Fetal role in parturition

• 1. Normal fetal adrenal-pituitary-hypothalamic axis for normal parturition.
• 2. Fetal stress leads to the release of corticotropin-releasing hormone (CRH), leading to ACTH release and subsequent fetal corticosteroid release from the adrenals. This has not been fully established in the dog (theory).
• 3. Fetal corticosteroid releases Prostaglandins (PGF2alpha) in some species
• 4. Fetal PGF2alpha directly stimulates uterine contraction (PGF2alpha is not increased in the uterus of the bitch), or enters the maternal blood stream to effect the release of oxytocin from the pituitary.
• 5. Progesterone inhibits myometrial cell contractility:
  • (a) In the ewe corticosteroid induced an enzyme the facilitates the metabolism of progesterone and leads to the observed decreased in this hormone. Progesterone decrease is a prerequesite to normal parturition.
  • (b) Canine placenta does not however produce progesterone.
  • (c) Fetal corticosteroid production is however required for normal parturition in the bitch. Bitches carrying a single fetus may have a prolonged gestation. Similar observation was also made in fetuses with defective hypothalamic-pituitary adrenal axis. 

5.3 Maternal factors in parturition

• 1. Normal parturition is initated by decrease in progesterone:estrogen ratio at the level of the myometrim:
  • (a) By increased estrogen concentration.
  • (b) Decrease progesterone:estrogen ratio facilitates oxytocin role in uterine contraction.
• 2. Decreased progesterone:estrogen ratio facilitates oxytocin role in uterine contraction
• 3. Entry of fetus in to birth canal results in the initiation of nerve impulses to the hypothalamus leading to further oxytocin release.
• 4. Relaxing. isolated in the placenta and ovary of several species causes the relaxation of the pelvic ligaments and increases the size of the birth canal. Relaxing may also aid in expanding the uterus to accomondiate the growing fetus.
• 5. Corticosteroids are elevated prior to parturition in the dog, however, the role of this hormone in lowering progesterone concentration is not fully established.
  • (a) Corticosteroid may be fetal or maternal origin.
  • (b) Progesterone is required for the maintenance of pregnancy.
  • (c) Corticosteroids may lower progesterone concentration, probably by enhancing its metabolism (theory) and such progesterone lowering may affect the pregnancy
  • (d) Administration of dexamethasone to the pregnant bitch at day 30 of gestation had resulted in intrauterine death followed by fetal resorption; Abortion occurred when such treatment was given at 45 days of gestation.
  • (e) For the above reason, corticosteroids should not be used in pregnant bitches during the period of gestation. 

5.4 Hematolgic changes occurring during pregnancy

• 1. PCV - decreases 7-9 weeks postestrus and bitches become anemic; such finding may occur in non-pregnant dogs during diestrus but the reduction in the PCV is less severe.
• 2. Serum cholesterol and protein may increase in both pregnant and non-pregnant bitches at diestrus.
• 3. Factor Vll. Vlll. IX. and Xl may increase at diestrus. in pregnant bitches only. 

5.5 Signalment of the onset of parturition

• 1. Hypothermia- drop of rectal temperature to below 100 F, 8-24 hours before parturition.
• 2. Decreased serum progesterone level; may go as low as 2 ng/ml. 

5.6 States Of Parturitution

Stage 1

• 1. Visible abdominal contraction coinciding with uterine contraction.
• 2. Passage of fetus through birth canal and delivery.
• 3. Distension of the birth canal by passage of the fetus results in the release of oxytocin which enhances uterine contraction; the distension of birth canal also evokes a spinal reflex called "Ferguson reflex" which precipitates the abdominal contractions.
• 4. Puppies are delivered every 30-60 minutes until completion but the interval between delivery may be up to 4hrs in normal births. (a) Average time for the completion of delivery is 6-1 2hrs. but could last up to 24hrs, in normal births.
• 5. Distress or disturbances may inhibit this stage.
• 6. Owner may notice a clear fluid from the vulva with the allantoic or the anionic membrane at birth.
• 7. Leaking of the pups by the bitch stimulates respiration and cardiovascular functions.
• 8. Approx. 60% pups born in anterior presentation; remaining pups born in breech or posterior presentation and that is normal.

 Stage 111

• 1. Often applicable for monotonous species and entails expulsion of the fetal membrane; in the dog the fetal membranes are passed at stage 11.
• 2. Locia, a thick greenish discharge accompanies placental separation may be observed in all the stages of parturition. This discharge is also call uteroverdin and is a product of rbc breakdown in the placenta. 

5.7 Uterine Involution

• 1. Occurs over several weeks post-parturition
• 2. Lochia may be discharged for up to 3 week postpartum.
• 3. Involution completed in approximately 3 months.
• 4. Subinvolution of placental sites (SIPS), characterized by bright red bloody discharge may be seen in younger dog (3yrs), several days postpartum and are not accompanied by systemic signs. This often resolves by the next estrus and on rare occasions, ovariohysterectomy may be indicated. 

5.8 Dystocia 

Guidelines for diagnosis:

1. Toxicity in the pregnant bitch:

• (a) Presence of systemic signs of toxicity.
• (b) Toxic signs seen 48-72 hrs. form onset.
• (c) Presence of lochia at the vulva is indicative of placental separation.
• (d) Entire litter are usually dead by 24 hrs after onset of dystocia.

2. Strong abdominal contraction with failure to deliver pups in 20 min.:

• (a) Indicative of entrapment of pups in the birth canal ("Ferguson's reflex)
• (b) Leads to uterine inertia.
• (c) Asphyxiation of pups with complete placental separation.

3. Weak staining with no pup deliver in 2-3 hrs. (a) Indicates that uterine contractions may not be adequate in bringing pups into birth canal.

4. More than 4 hours has elapsed since delivery of the last puppy. 

• (a) Indicate completion of parturition.
• (b) Uterine inertia.
• (c) Pups have been delivered alive after 4 hrs delay by the incidence of stillbirth rises around this time.

5. Prolonged gestation

• (a) Evaluate for dystocia if 68 days has elapsed since last mating.
• (b) Beware of pseudopregnancy.

6. (c) Observation of pup at the vulva lips by owner with no expulsion

7. Abnormal vulva discharge:

• (a) Lochia-indicative of placental separation, with no delivery,
• (b) A copious clear watery discharge; suggests passage of allantoic and or anionic fluid, with no delivery.
• (c) Severe hemorrhage from vulva; indicative of traumatic birth. 

5.8.1 Types of dystocia

Types:

maternal and fetal factors. 

5.8.1.1 Fetal factors:

• 1. Oversized fetus; a single pup, a breed with predisposition to large head or shoulder e.g brachycephalic breeds.
• 2. Fetal monsters, hydrocephalus, anarsarca, hypothalamic-pituitary adrenal axis abnormalities. 

5.8.1.2 Maternal factors

• 1. Decreased size of the pelvic Canal:
  • (a) Pelvicfractures.
  • (b) Breed predisposition.
• 2. Abnormalities in the Vagina
  • (a) persistent hymen
  • (b) Vaginal bands
  • (c) Vestibulovaginal strictures
  • (d) Vaginal hypoplasia
• 3. Uterine malfunction:
  • (a) Uterine inertia - dachshunds and Scottish terriers and St. Bernard
  • (b) Uterine torsion
  • (c) Uterine rapture
• 4. Bulldogs may experience inadequate abdominal contraction during parturition. 

5.9 Uterine inertia

• 1. Primary: contraction defect not resulting from any recognizable factor; seen in St. Bernard breed; often normal size pups.
• 2. Secondary: the result of uterine fatigue following obstructive dystocia or overstretching of the uterine myometrium; may be the result of large pups
• 3. Bitches with uterine inertia will not respond to oxytocin administration.
• 4. Bitches with uterine inertia may not exhibit the "Ferguson's reflex". 

5.10 Medical management of dystocia

• 1. USE of ecobolics: Indicated in non-obstructive dystocias:
  • (a) Omytocin: Most commonly used ecbolic; short duration of action; 5-20 units every 30 minutes, IM. (i) Enhances placental separation and so, failure to deliver pups within the first hour of administration, will be an indication for surgical intervention.
  • (b) Hot drugs: not often used; have longer duration of action; inhibits prolactin release: more likely to cause uterine rapture.
  • (c) Calcium solution: required for myometrial contraction; used only in hypoclcemic states ( eclamcia ). 

5.11 Obstetrical management of dystocla

• 1. Pervagoma; correction of fetal position and assisted extraction. Care should be taken to avoid trauma to fetus during manipulation.
• 2. May employ forces to assist extraction- same precaution as above.
• 3. Lubrication with K-Y jelly may facilitate extraction and minimize trauma. 

5.12 Surgical management

Caesarean section:

refer to your surgery notes.

Assignments:

• 1. Review parturition in the cat.
• 2. Review pseudopregnancy in the dog and cat.