9 - Labour and Delivery

Question 1

What happens to progesterone and why at the onset of labour?

Answer 1

Progesterone is withdrawn as progesterone prevents contractions

Question 2

What occurs in the foetal adrenals at the onset of labour?

Answer 2

Foetal adrenals produce more DHEAs which is converted by the placenta to oestrogen

Question 3

What is the role of oestrogen in the onset of labour?

Answer 3

Oestrogen promotes the release of prostaglandins from the decidua and foetal membranes

Question 4

What are the two types of prostaglandin?

Answer 4

E2 and F2a

Question 5

What do PG do?

Answer 5

Promote cervical ripening

Stimulate contractions

Question 6

How does prostaglandin stimulate contractions?

Answer 6

Acts directly on the myometrium and increases the expression of oxytocin receptors

Question 7

What is the difference between F and E prostaglandins?

Answer 7

F - contractant - release stimulated by oestrogen

E and I - relaxants - release stimulated by progesterone

Question 8

What is ripening of he cervix?

Answer 8

Increase in distensibility

Collagen conc decreases and is replaced by amorphous substance

Question 9

What changes on the myometrium does prostaglandins induce?

Answer 9

Cell to cell adhesion

Increase levels of oxytocin

Question 10

What is the function of oxytocin in the myometrium?

Answer 10

Attach to receptors

Stimulate contractions - top downwards

Question 11

What is the ferguson reflex?

Answer 11

foetus contacts baroreceptors in the cervix
stimulates and sends impulse to brain
Oxytocin released
Ocytocin binds to receptors in the myometrium and causes contraction
Baby pushes further into the cervix so another contraction is stimulated

Question 12

What are the signs of labour?

Answer 12

Release of the mucous plug which seals the opening of the cervix
Rupture of membranes - breaking of the waters
Painful contractions - Last longer than 40 seconds (in labour)

Question 13

How do you diagnose labour?

Answer 13

Progressive cervical dilation
Regular, painful uterine contractions - lasting for 40 seconds or longer
The show
Backache

Question 14

What occurs in the first stage of labour?

Answer 14

0-10cm cervical dilation

rate of more than 1cm/hour

Question 15

What are braxton hicks contractions?

Answer 15

Painful, rhythmic contractions occurring every 2-3minutes

Question 16

What happens to the upper and lower segments of the uterus during the first stage of labour?

Answer 16

Upper segment of the uterus - heaped up

Lowe segment - passively thins and stretches

Question 17

What is the difference between the latent and active phase?

Answer 17

o	Latent phase
	0-3cm cervical dilation 
o	Active phase
	3-10cm cervical dilation 
	Primigravida = 1-3cm/hour 
	Multigravida = 3-6cm/hour

Question 18

What occurs in the 2nd stage of labour?

Answer 18

o Full dilation to expulsion of the foetus
o Uterus and vagina form a continuous tube
o Uterine contractions supplemented by voluntary contraction of the abdominal muscles and fixing the diaphragm to increase intra-abdominal pressure
o Pelvic floor muscles stretched backwards

Question 19

What is the difference between the propulsive and expulsive phase?

Answer 19

o Propulsive phase = full dilation to presenting part reaching the pelvic floor
o Expulsive phase = from reaching pelvic floor to delivery of baby

Question 20

What are the times for the 2nd stage of labour?

Answer 20

o Primigravida = 40 minutes

o Multigravida = 20 minutes

Question 21

What occurs in the 3rd stage of labour?

Answer 21

o Expulsion of the foetus to expulsion of placenta
o Both primigravidae and multigravidae = 20-30 minutes
o Uterine muscles contract tonically to constrict blood vessels passing through interlacing fibres
o Placenta separates as the placental bed is constricted down to half its size and is expelled by uterine contractions moving caudally

Question 22

What is a collapsable skull?

Answer 22

membranes not get fully ossified – can override each other to reduce the dimensions of the skull to fit through the pelvic outlet

Question 23

What is the passage of giving birth?

Answer 23

o Curve of carus
o Curved passage
o Gynaecoid
 Wide, obtuse pubic arch
 No ischial spines protruding into the pelvic outlet
 Wide birth canal
 Station 0 (between two ischial spines) > 10 cm

Question 24

What gives the mother power to go through labour?

Answer 24

o	Pelvic floor 
	Support pelvic viscer
	Help build continence 
	Build up effectvie intra-abdominal pressure 
	Helps rotation of the presenting part

Question 25

What is an episotomy?

Answer 25

 Vaginal epithelium, perineal skin, bulbocavernous muscle, superficial and deep perineal muscles and occasionally external anal sphincter cut