Parturition and dystocia Flashcards
List the 3 stages of parturition
1) Initiation of myometrial contraction
2) Expulsion of the foetus
3) Expulsion of the foetal membranes
What initiates parturition?
-Hormonal signals from foetus= FOETAL CORTISOL
What does puerperium mean?
Stage between parturition and when cycle starts again
What does the stage of preparation for parturition involve?
- Production of relaxin
- Relaxin= produced in placenta of horse/ dog/ cat but produced in CL in ruminants/ sow
- Relaxin causes increased elasticity of the pubic symphysis, vulval and perineal tissues
Describe stage 1 of parturition
- Increased foetal cortisol- enzymes activated which switch P4 to E2- increased E2 causes increased repro tract secretions (lubrication)- decreased P4 removes inhibition on myometrial contractions
- Increased foetal cortisol also causes increased prostaglandin which causes lysis of CL (if present) and also increases relaxin to remodel cervix etc
What effect do uterine contractions have on the placenta?
-Cause the placental attachments to the endometrium to loosen.
What are the signs of first stage parturition?
- Uterine (not abdominal) contractions
- Shivering
- Nesting behaviour
- Vulval discharge
In which type of species can second/ third stage parturition not be separated?
-Polytocous
What are the signs of second stage parturition?
-Onset of abdominal contractions
Describe Fergusons reflex
- Abdominal/ uterine contractions–> push foetus against cervix –> neuro–hormonal reflex stimulated causing the brain to release oxytocin –> results in myometrial contractions
- Fergusons reflex is separate to the abdominal contactions!
How much of the workload do uterine contractions do?
90%
What is the stimulus to breathing?
The air hitting the nostrils
When the umbilical ruptures, what prevents haemorrhage?
-The two umbilical arteries and urachus retract into the abdomen
Describe the events that occur during second stage parturition
- Abdominal/ uterine contractions
- Fergusons reflex (NOT part of abdominal contractions)
- ALLANTOCHORION ruptures due to movement against vulva
- Contractions continue and AMNION ‘water bag’ is visible
- Foetus becomes hypoxic once enters the birth canal
- Forceful contractions continue
- Foetus either both inside amnion or it ruptures during birth.
During third stage parturition what do the uterine contractions do?
- Cause the opening of endometrial crypts
- Removal of the placenta
- Separation of the foetal membranes
Describe the expulsion of the placenta in the mare
- Has a diffuse placenta so the apex of the allantochorionic sac starts to invert as the foal exits
- Foal bursts through the cervical start within the amnion and the placenta everts as it is pulled out
- When the placenta is out it is the allanchoic (fetal) side you see
What happens during puerperium?
-The reproductive tract reduces in size similar to that before pregnancy
Define the term foetal disposition
The spatial arrangement of the foetus relative to the pelvis and the birth canal of the dam
What does the foetal position indicate?
- The quadrant of the dam’s birth canal that the foetus’ vertebrae is next to
- Dorsal position, ventral position, right lateral position, left lateral position
What does the term foetal posture relate to?
The disposition of the moveable appendages of the foetus, involves flexion/ extension of the neck and limb joints e.g. diving position is in the extended posture
What are the common causes of dystocia?
- Foetus too big/ too small
- Abnormal foetal disposition
- Multiple foetuses
- Uterine inertia
In dogs what is the primary cause of dystocia?
-Primary intertia
What is the term used for correcting presentation, position or posture?
Mutation
What is repulsion?
Pushing the fetus out of the pelvis and back into the abdomen to give you more room to reposition
What angle gives the largest diameter of the birth canal?
5 past 7 or 5 to 5
i.e. diagonal
Why do you have to be careful once the foetus enters the birth canal?
- The umbilical cord is obstructed and so the foetus becomes hypoxic.
- Once the umbilicus engages the pelvis you have to deliver very fast. Especially if in caudal longitudinal presentation.
