Parturition and dystocia Flashcards
(32 cards)
Describe the stage of preparation in parturition
production of relaxin (polypeptide hormone) from placenta (CL in sow)
Causes relaxation of pubic symphysis, vulval and perineal tissues
Describe the first stage of parturition - onset of uterine contractions
Fetus produces cortisol:
- cortisol enzymes convert progesteone to oestradiol
- progesterone decline removes myometrial contraction block
- increased basal uterine contractions
- elevated oestrogen increases reproductive tract secretions -> lubrication
Cortisol => increased uterine prostaglandin:
- lysis of CL
- uterine contraction due to increased PGF2a and oestrogen
- relaxin production causes degradation and remodelling of cervical matrix and cervical os opens
How do uterine contractions cause haemorrhage in species with deciduate placentas?
Placental attachments to endometrium become less intimate
Superficial cells undergo fatty degeneration
Separation of margins begins => haemorrhage
What are the signs of the first stage of parturition?
Describe the 2nd stage of parturition - expulsion of the fetus
Fergusons reflex
Allantochorion ruptures as it moves towards cervix - allantoic fluid escapes from vulva
Contractions continue, amnion appears at vulva (water bag)
Fetal limbs appear in amnion
Fetus becomes hypoxic as it enters birth canal - promotes foetal movement which stimulates myometrial contractions
Foetal head reaches vulva - climax of uterine and abdominal muscle effort
Foetus expelled
Describe the Fergusons reflex in the second stage of parturition
Fergusons reflex:
- abdominal and uterine contractions
- force fetus against cervix
- neuro-hormonal reflex
- brain release of oxytocin
- myometrial contractions
What stimulates the foetus to breath after parturition?
air hitting nostrils
What happens to the umbilical cord after parturition?
The cord ruptures after some time
Then the umbilical arteries and urachus retract into the abdomen to prevent haemorrhage
What is the risk of premature rupture of the umbilical cord?
deprive newborn of large volume of blood which would normally pass from the placenta
What happens to the amnion after/during birth?
May rupture during birth
Fetus may be delivered within the amnion and movement ruptures it
Describe the 3rd stage of parturition - expulsion of placenta
Regular abdominal contractions cease
Myometrial contractions decrease in amplitude, become less regular but become more frequent
Lack of foetus results in vasoconstriction of arteries supplying chorionic villi - villi decrease in size and release from crypts
Uterine contractions cause:
- opening of endometrial cups
- exsanguination/loss of blood from placenta
- separation of the foetal membrane
When inverted membranes form a mass in pelvis => reflex abdominal contractions
Allantochorion/placenta is expulsed
What is the puerperium
the period after expulsion of the placenta where the repro tract reduces in size to that before pregnancy
~2-8weeks
What is this foetal presentation?
Cranial longitudinal presentation
dorsal position
extended posture
What is this foetal position?
Caudal longitudinal presentation
dorsal position
extended posture
What is dystocia?
difficult birth
What are the common causes of dystocia?
foetus too big
dam too small
abnormal foetal position
multiple foetuses
poor or absent uterine contractions (primary or secondary intertia)
What is the most common reason for dystocia in cows?
big calf
abnormal dispositionq
What are the possible foetal presentations and positions?
Presentation:
- cranial longitudinal
- caudal longitudinal
- dorsal transverse
- ventral transverse
Position:
- dorsal
- ventral
- left lateral
- right lateral
Why is dystocia an emergency in mares?
2nd stage of parturition is very short (~30 mins)
What are the ways to manage dystocia?
Drug therapy:
- oxytocin => contractions
- clenbuterol (tocolytic) => stops contractions
Surgical treatment:
- epidural anaesthesia => stop contractions
- episiotomy - enlarge birth canal
- fetotomy
- caesarean
Euthanasia
Manipulation of foetus - MUTATION
What is traction used for in managing parturition?
provided at the time of contractions to aid expulsion
also helps allow foetal breathing
What methods are there for providing traction to live and dead foetuses?
Live:
- calving jack
- head/neck snare
- vectis forceps
Dead:
- chains
- eye hooks
- self closing hooks
What should you do after delivery in a dystocia?
check there are no other foetuses
Check for lacerations and perforations
ensure no defects such as pelvic fractures
Consider analgesia, antimicrobial therapy
What is primary and secondary inertis?
Primary uterine inertia is the failure to initiate contractions at parturition. Secondary uterine inertia is the failure to progress once contractions are initiated (uterine fatigue)
