Parturition and Dystocia Flashcards
What two things stimulated by fetal cortisol during the first stage of parturition?
Increase in enzymes that convert progesterone to oestradiol – removes the block on myometrial contractions, increases reproductive tract secretions
Increase in uterine prostaglandin – lysis of the CL, increased uterine contraction, relaxin production which causes degradation of collagen and remodelling in the cervix
How do uterine contractions affect the placenta?
Cause the placental attachments to the endometrium to become less intimate
What is the first sign of the second stage of parturition?
Onset of abdominal contractions, superimposed upon the beginning of specific myometrial contractions significantly increasing uterine pressure
What is Fergusons reflex?
Abdominal & uterine contractions -> force fetus against cervix -> neuro-hormonal reflex -> brain releases oxytocin ->myometrial contractions
What nucleus is involved in Fergusons reflex?
Paraventricular nucleus
What happens to the allantochorion?
Ruptures as a consequence of its movement towards the cervix
When do uterine and abdominal contractions reach a climax?
When the fetal head reaches the vulva
What is the stimulus to breathe?
Impact of air at the nostrils
If the umbilical cord is attached, why is it important to allow this to rupture naturally?
Artificial or premature rupture may deprive the newborn of a large volume of blood which would normally pass from the placenta
How is haemorrhage prevented upon rupture?
The two umbilical arteries and urachus retract into the abdomen
What happens after fetal expulsion?
Regular abdominal contractions largely cease, myometrial contractions decrease in amplitude but become more frequent and less regular, lack of fetus results in vasoconstriction of the arteries supplying the chorionic villi
What is caused by uterine contractions during the third stage of parturition?
Opening of endometrial crypts, exsanguination of the placenta, separation of the fetal membranes
What happens in the mare (diffuse placentae)?
The apex of the allantochorion sac becomes inverted and the sac is ‘rolled’ down the uterine horns, as such the allantois membrane appears on the outside
What stimulates the reflex abdominal contractions?
When a large portion of the inverted membranes form a mass within the pelvis
What happens during puerperium?
Reproductive tract reduces in size to similar to that before pregnancy
What is fetal disposition?
The term used to describe the spatial arrangements of the fetus in relation to the pelvis and birth canal of the dam, and of its extremities to itself
What are the three terms used to describe disposition in greater detail?
Presentation, position and posture
What does fetal presentation describe?
The relation between the longitudinal axis of the fetus and the maternal birth canal – longitudinal or transverse
What does fetal position describe?
Indicates the surface of the maternal birth canal to which the vertebral column of the fetus is apposed – dorsal, ventral, left lateral or right lateral
What does fetal posture describe?
The disposition of the moveable appendages of the fetus – flexion or extension
What factors influence the incidence of dystocia?
Species, breed, age, parity, body conditions, environment
What are the common causes of dystocia?
Fetus too big or dam too small, abnormal fetal disposition, multiple fetuses, poor or absent uterine contractions (primary & secondary inertia)
What are the most common causes of dystocia in cows?
Feto-maternal disproportion, fetal disposition, incomplete vaginal/cervical dilation, uterine inertia, uterine torsion, cervical prolapse, fetal monsters
What types of treatment should be considered when managing dystocia?
Conservative treatment, manipulative treatment, drug therapy, surgical treatment, euthanasia
