4.1/2. 1st & 2nd stage of labour

Question 1

Which hormone prevents the uterus from contracting during pregnancy?

Answer 1

Progesterone

Question 2

Of which sort of muscle cell is the uterus comprised?

Answer 2

Smooth muscle

Question 3

Explain 3 factors which characterise the latent phase of labour

Answer 3

1. Effacement- cervix thins out and merges into the lower uterine segment. The internal os is closed.
2. Show- as cervix ripens, thins and effaces, mucous plug dislodged
3. Dilatation- cervix may dilate up to 4cm
   other: lightening, cervical ripening, spurious labour

Question 4

Where in the uterus are the most dense contractions of the muscle cells?
why is this important?

Answer 4

Fundus/ top of uterus

As they contract and retract, lower uterine segment is pulled up, causing cervical dilatation.

Question 5

State 2 factors thought to play a part in the onset of labour

Answer 5

Two of:

Prostaglandins, calcium ions, oestrogen, oxytocin receptors, feto-placental unit, mechanical factors

Question 6

What is ‘retraction’ in labour?

why is it important?

Answer 6

Contractions cause muscle fibres in the uterus to become shorter and thicker. As each contraction recedes, some of the shortening is retained, the muscles do not relax back completely. This retraction pulls the lower segment of the uterus, and the cervix up- causing cervical dilatation.

Question 7

What is meant by fundal dominance?

Answer 7

Contractions start in the fundus near the cornea. They then spread across and down the body of the uterus.

Question 8

What is the ‘expulsive’ phase of the 2nd stage?

Answer 8

Cervix is fully dilated AND feels need to push

Question 9

What is the ‘ferguson reflex’ and how does it work to encourage expulsive contractions?

Answer 9

1. Fetal head meets pelvic floor and stimulates nerve receptors
2. Message sent to pituitary- secretes oxytocin into blood and to uterine muscle
3. Oxytocin stimulates uterine contractions causing further fetal descent
4. More pressure from fetus onto pelvic floor- more stimulation of nerve receptors

Question 10

Give 2 examples of soft tissue displacement as the fetus descends through the pelvis

Answer 10

1. Bladder is pushed upwards into the abdomen
2. The rectum becomes flattened into the sacral curve

other: urethra stretched and thins out so lumen reduced, perineal body flattened stretched and thinned, levator ani muscles dilate thin out and are displaced laterally

Question 11

Explain the process of internal rotation in the mechanism of labour

Answer 11

When the occiput meets the resistance of the pelvic floor, it rotates forward approx. 45 degrees. This means the head is now facing the mother’s back. The widest part of the head (anteroposterior diameter) is now aligned with the widest part of the pelvic outlet.