Parturition and Dystocia

Question 1

What two things stimulated by fetal cortisol during the first stage of parturition?

Answer 1

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

Question 2

How do uterine contractions affect the placenta?

Answer 2

Cause the placental attachments to the endometrium to become less intimate

Question 3

What is the first sign of the second stage of parturition?

Answer 3

Onset of abdominal contractions, superimposed upon the beginning of specific myometrial contractions significantly increasing uterine pressure

Question 4

What is Fergusons reflex?

Answer 4

Abdominal & uterine contractions -> force fetus against cervix -> neuro-hormonal reflex -> brain releases oxytocin ->myometrial contractions

Question 5

What nucleus is involved in Fergusons reflex?

Answer 5

Paraventricular nucleus

Question 6

What happens to the allantochorion?

Answer 6

Ruptures as a consequence of its movement towards the cervix

Question 7

When do uterine and abdominal contractions reach a climax?

Answer 7

When the fetal head reaches the vulva

Question 8

What is the stimulus to breathe?

Answer 8

Impact of air at the nostrils

Question 9

If the umbilical cord is attached, why is it important to allow this to rupture naturally?

Answer 9

Artificial or premature rupture may deprive the newborn of a large volume of blood which would normally pass from the placenta

Question 10

How is haemorrhage prevented upon rupture?

Answer 10

The two umbilical arteries and urachus retract into the abdomen

Question 11

What happens after fetal expulsion?

Answer 11

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

Question 12

What is caused by uterine contractions during the third stage of parturition?

Answer 12

Opening of endometrial crypts, exsanguination of the placenta, separation of the fetal membranes

Question 13

What happens in the mare (diffuse placentae)?

Answer 13

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

Question 14

What stimulates the reflex abdominal contractions?

Answer 14

When a large portion of the inverted membranes form a mass within the pelvis

Question 15

What happens during puerperium?

Answer 15

Reproductive tract reduces in size to similar to that before pregnancy

Question 16

What is fetal disposition?

Answer 16

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

Question 17

What are the three terms used to describe disposition in greater detail?

Answer 17

Presentation, position and posture

Question 18

What does fetal presentation describe?

Answer 18

The relation between the longitudinal axis of the fetus and the maternal birth canal – longitudinal or transverse

Question 19

What does fetal position describe?

Answer 19

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

Question 20

What does fetal posture describe?

Answer 20

The disposition of the moveable appendages of the fetus – flexion or extension

Question 21

What factors influence the incidence of dystocia?

Answer 21

Species, breed, age, parity, body conditions, environment

Question 22

What are the common causes of dystocia?

Answer 22

Fetus too big or dam too small, abnormal fetal disposition, multiple fetuses, poor or absent uterine contractions (primary & secondary inertia)

Question 23

What are the most common causes of dystocia in cows?

Answer 23

Feto-maternal disproportion, fetal disposition, incomplete vaginal/cervical dilation, uterine inertia, uterine torsion, cervical prolapse, fetal monsters

Question 24

What types of treatment should be considered when managing dystocia?

Answer 24

Conservative treatment, manipulative treatment, drug therapy, surgical treatment, euthanasia

Question 25

What does mutation (correcting the presentation, position or posture) comprise?

Answer 25

Repulsion, correction & rotation or version

Question 26

When is traction best applied?

Answer 26

At the time of the dam’s contractions, helps allow fetal breathing

Question 27

In small animals how is traction provided?

Answer 27

Via a head snare, neck snare, or using vectis forceps

Question 28

Where is the largest diameter of the birth canal?

Answer 28

Ten-past-eight or ten-to-four

Question 29

When is it important that the fetus is delivered rapidly?

Answer 29

When the umbilicus engages the pelvis, particularly in posterior presentation

Question 30

After delivery why do you examine the dam?

Answer 30

To ensure that there is no other fetus, that there are no lacerations or perforations & that there are no obvious other defects such as pelvic fractures or mastitis