Dystocia

37 Dystocia


Telephone enquiries regarding possible cases of dystocia are relatively common in companion animal emergency practice. Owners are often anxious and distressed at these times and veterinary staff must have a good understanding of normal gestation and parturition in order to provide sound logical advice.



Theory Refresher



Normal gestation and parturition



The bitch



Normal gestation


Average length is 65 days (range 56–72 days). This range reflects the variable correlation between copulation and actual fertilization in the bitch. Once fertilization actually occurs, the true gestation length is less variable.



Labour


Labour is divided into three stages.



First stage

Stage one occurs 24–48 hours before parturition. Behavioural changes may include:


• Nesting behaviour

• Restlessness

• Panting

• Attention-seeking or being seclusive

• Shivering

• Inappetence

• Vomiting.

Physical changes may include:


• Mammary gland changes and lactation 1–7 days before parturition

• Marked decrease in body temperature 8–24 hours before parturition (typically found to be 35–37°C)

• Progressive cervical dilation and vaginal relaxation

• Initiation of subclinical uterine contractions (no abdominal straining).


Second stage

Stage two occurs 3–24 hours before parturition. There are three cardinal signs indicating that the dam is in stage two although all three signs may not be present in any individual case.


• Body temperature increases to normal or slightly above normal

• Abdominal contractions begin (concomitant with strong uterine contractions)

• Clear fluid is discharged from the vulva – this is fluid from the ruptured chorioallantois and usually signifies delivery of the first neonate within 30 minutes to 4 hours. Allantoic fluid should precede each neonate.

A green vulval discharge is normal in the bitch as long as it is produced less than 2 hours before, with, or after foetal delivery. This discharge is due to placental separation. Following delivery the dam should remove the amniotic membranes, sever the umbilical cord, and clean and bond with the foetus.



Third stage

Stage three represents expulsion of placental and foetal membranes and occurs concurrently with stage two in pluriparous dams. Expulsion usually occurs within 15 minutes of delivery but the dam may deliver two or more foetuses before any membranes are expelled. Maternal consumption of the membranes may induce gastrointestinal signs and should be discouraged. Discharge of residual foetal fluids and placental remains may persist for 3–6 weeks after parturition has ended. However failure to pass the majority of all placentas within 4–6 hours of the end of second stage labour should prompt veterinary attention.



The queen


Gestation and parturition in the queen are similar to the bitch with a few noteworthy exceptions.


• Normal gestation in the queen is 63–67 days. This narrower range reflects the induced ovulation that occurs in this species.

• It is not uncommon for a queen to disappear from the home during stage one labour, leaving owners unaware of the changes occurring.

• Body temperature may decrease in the 12 hours prior to parturition but this is a less consistent finding.

• In the queen normal vulval discharge due to placental separation is red-brown in colour (green in the bitch).


Dystocia


The incidence of dystocia in dogs and cats is reported to be approximately 5% and dog breeds that may be at increased risk include chondrodysplastic and brachycephalic breeds, especially Pugs and Bulldogs, as well as Scottish terriers, Boston terriers, Yorkshire terriers and the Chihuahua. Dystocia is most common in short-faced breeds as well as Devon Rex and Siamese cats. Primary uterine inertia is the most common cause of dystocia in dogs and cats and is a maternal cause. Other maternal causes include mechanical obstruction (e.g. due to narrowing of the pelvic canal secondary to healed fractures), maternal anxiety and systemic illness. Foetal malpresentation is the most common foetal cause of dystocia in dogs and cats. Others include foetal oversize, malformation and death.



Clinical Tip



• If a dam is in active labour the stress of transportation and veterinary examination may endanger the life of a foetus that is in the birth canal and undergoing normal parturition. Attempting to progress parturition at home must, however, be balanced with the realization that the sooner cases that require veterinary attention receive this treatment the more likely it is that a successful outcome will be achieved (see Box 37.1).


BOX 37.1 Indications for veterinary attention during parturition



• Prolonged gestation: due date (if known) reached without signs of labour

• A history of previous dystocia

• More than 24 hours of anorexia in the full-term queen

• No signs of labour more than 24 hours after the decrease in body temperature in the full-term bitch

• No signs of labour 12–24 hours after body temperature increases again in the full-term bitch

• More than 4 hours since the onset of second stage labour without a foetus being passed

• Strong active but nonproductive abdominal contractions for more than 30 minutes

• Flank biting or other signs suggesting severe abdominal discomfort in the dam

• A green (bitch) or brown (queen) vulval discharge without a foetus being born in the subsequent 2 hours

• Sanguineous or malodorous vulval discharge

• Weak irregular nonproductive straining for more than 2 hours

• More than 2–4 hours between foetuses being delivered

• Failure to deliver all foetuses within 24 hours (bitch) or 36 hours (queen) from the onset of second stage labour

• Signs of systemic compromise in the dam

• The presence of a foetus or foetal membranes protruding from the vulva for more than 15 minutes

Note that posterior presentation is considered to be a normal variation in dogs and cats.



Oxytocin


Oxytocin is a hormone that is released during labour and that causes uterine smooth muscle contraction as well as milk letdown. It is used to treat dystocia due to uterine inertia by increasing the frequency and strength of uterine contractions which it does by promoting calcium influx into myometrial cells. Oxytocin also promotes uterine involution after birth as well as reducing uterine haemorrhage and assisting in expulsion of retained placentas.



Clinical Tip



• The use of oxytocin is contraindicated in the presence of pelvic obstruction, inadequate dilation of the cervix, vaginal masses or strictures, and inguinal hernias.

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Dystocia

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