Session 10 - Birth

Question 1

What occurs in the first stage of labour?

Answer 1

• Creation of birth canal
• Onset of labour –> full cervical dilation

Question 2

What occurs in the second stage of labour?

Answer 2

• Expulsion of the fetus
• Can take up to 1 hr
• Head flexes, rotates, and then stretches vagina and perineum with a risk of tearing. After head is delivered, the shoulders rotate and deliver and the rest follows.

Question 3

What occurs in the 3rd stage of labour?

Answer 3

• Expulsion of placenta
• Contraction of uterus to compress blood vessels and reduce haemorrhage
• lasts up to 15 mins

Question 4

What soft tisseues need to expand to create a birth canal?

Answer 4

• Cervix
• Vagina
• Perineum

Question 5

To what size does the birth canal expand to?

Answer 5

~10 cm

Question 6

What is the maximum size of the birth canal and the normal diameter of the fetal head?

Answer 6

head - 9.5 cm

pelvic inlet - 11 cm after softening of ligaments

Question 7

What is cervical ripening? What triggers it?

Answer 7

Cervix made of tough thick coiled collagen

ripening involves - reduction in collagen production, increase in glycosaminoglycans (dirupts matrix), and uncoiling.

Triggered - prostaglandins PG E2 and F2x.

Question 8

How is myometrial contractions triggered?

Answer 8

triggered by pacemakers and force generated by increased intracellular calcium

Question 9

What substances strengthen and suppress the myometriums contractions?

Answer 9

strengthens - prostaglandins, oxytocin

suppresses - progesterone

Question 10

How does the uterus contract during early and late pregnancy?

Answer 10

Early - low amplitude every 30 mins

Late - higher amplitude, less frequent. Braxton-Hicks contractions

Question 11

How is prostaglandin production controlled?

Answer 11

by oestrogen:progesterone ratio

Progesterone > oestrogen = low prostaglandins, throughout pregnancy

Oestrogen > progesterone = high prostanglandins, end of pregnancy

Question 12

What is the ferguson reflex?

Answer 12

Upon application of pressure to the internal end of the cervix, oxytocin is released, which stimulates uterine contractions, which in turn increases pressure on the cervix (thereby increasing oxytocin release, etc.), until the baby is delivered.

Question 13

What is brachystasis?

Answer 13

Uterine smooth muscle relaxes less than it contracts which shortens the body of the uterus over time and forces the baby out

Question 14

What happens to fetal cortisol, oestrogen and progesterone, prostaglandins, cervix, oxytocin during labour?

Answer 14

• Fetal cortisol increases
• Oestrogen > progesterone
• Increased prostaglandins
• Cervix stretched
• Oxytocin released from post pit - ferguson reflex

Question 15

What is the apgar score?

Answer 15

Score assessing condition of neonate

Question 16

How is maternal blood loss limited post birth? How is this process enhanced?

Answer 16

• uterus contracts post birth, shearing off and expeling placenta
• uterine contractions compresses blood vessels and closes them
• Can be enhanced by giving oxytocic drug

Question 17

What is the most common position that the baby lies?

Answer 17

longitudinally, cephalic presentation and well flexed

Question 18

How can inadequate power, passahe or abnormalities of the passenger lead to failure to progress in labour?

Answer 18

• Inadequate power - insufficient uterine contraction
• Inadequate passage - abnormal bony pelvis, rigid perineum
• Abnormalities of passenger - fetus too big or breech presentation

Question 19

How can you induce labour?

Answer 19

giving prostaglandins and oxytocic drugs

Question 20

What instruments are used for operative delivery?

Answer 20

forceps or vaccuum extraction

Question 21

Where is a c section made?

Answer 21

suprapubic or hypogastric

Question 22

What are the effects of oestrogen on oxytocin receptor production in the myometrium?

Answer 22

increases

Question 23

What effect does progesterone have on the responsiveness of the uterus to oxytocin and prostaglandin release?

Answer 23

reduces both

Question 24

Why is progesterone necessary to avoid spontaneous abortions?

Answer 24

Prevents oxytocin from evokning contractions during pregnancy and positive feedback mechanism of oxytocin

Question 25

What postural change could occur from ostrogen mediated softening of the ligaments in the pelvis?

Answer 25

lordosis

Question 26

what anatomical landmark gives an estimate for 20 weeks of gestation?

Answer 26

mothers umbilicus

Question 27

What fetal landmark is used to assess fetal head position in the birth canal?

Answer 27

fetal fontanelles

Question 28

What spinal segments does the epidural block?

Answer 28

T9-S4

Question 29

Define post partum hemorrhage

Answer 29

>500 ml blood loss after delivery

Question 30

what is the most common cause of PPH?

Answer 30

uterine atony