Labour and Delivery

Question 1

Describe the ripening of the cervix and why this is needed. (5)

Answer 1

The cervix is collagen fibres embedded in a proteoglycan matrix. Ripening decreases collagen fibres and increases GAGs which ‘loosens’ the collagen. An influx of inflammatory cells and increased NO- output caused by prostaglandins also helps.
It is needed so the cervix can dilate to 10cm to fit a baby though.

Question 2

Describe Brixton-Hicks contractions. (3)

Answer 2

Spontaneous contractions of the myometrium that are low amplitude, high frequency in early pregnancy, and high amplitude, low frequency in late pregnancy.

Question 3

Describe the causes of the sudden increase in frequency and amplitude in contractions in labour. (4)

Answer 3

Prostaglandins: enhance the release of calcium from intracellular stores to increase the frequency of action potentials that prompt actin and myosin to contract.
Oxytocin: peptide hormon that acts to lower the threshold for an action potential, meaning less calcium is needed.

Question 4

Describe the reflex that increases oxytocin. (2)

Answer 4

Ferguson reflex.

Increases oxytocin secretion massively in a positive feedback loop.

Question 5

Define brachystasis in relation to the uterus. (2)

Answer 5

A not-full relaxation that causes the fundal region to progressively shorten.

Question 6

What triggers the production of progesterone and oxytocin? (1)

Answer 6

A fall in progesterone compared to oestrogen.

Question 7

What can you give a mother to induce labour? (1)

Answer 7

Prostaglandins and oxytocin.

Question 8

Describe the “lie” of the foetus. (3)

Answer 8

Relationship of the long axis of the foetus relevant to the long axis of the uterus. Commonest is longitudinal (head or butt first). The foetus often also has a flexed neck - a “flexed attitude”.

Question 9

Describe the “presentation” of the foetus. (4)

Answer 9

Which part of the foetus is going to emerge first. Can be cephalic (head) or breach (butt) or weirdness with legs or shoulders or arms, which can cause problems because it increases the diameter of the birth canal over 10cm.

Question 10

Define the second stage of labour. (1)

Answer 10

The time between full dilation of the cervix and delivery of the foetus.

Question 11

Define the first stage of labour. (2)

Answer 11

The interval between the onset of labour and full dilation of the cervix, including descent of the foetal head into the birth canal and rupture of the membranes.

Question 12

Describe the stages of delivery of the foetus. (4)

Answer 12

The descended head flexes (if baby is face to back) to reduce the diameter of presentation.
Internal rotation of the head.
Head descends to vulva, stretching of the vagina and peritoneum, and is delivered (crowning), extending the neck.
Shoulders rotate and are delivered followed by the rest of the foetus.

Question 13

Describe the cause and consequence of shoulder dystocia. (2)

Answer 13

Shoulders get stuck

Erb’s palsy with an upper brachial plexus injury.

Question 14

Describe the third stage of labour. (2)

Answer 14

With the foetus removed, the uterus contracts powerfully to compress blood vessels attached to the placenta (prevents PPH) and expels the placenta.

Question 15

Describe how the foetus establishes its circulation in the adult form. (6)

Answer 15

Foetus takes its first breath in response to stimuli like light, cold, noise. This causes a fall in pulmonary resistance, so reduces PA pressure, increasing LA pressure > RA pressure. This closes the foramen ovale and higher p(O2) causes the ductus arteriosus to constrict. The ductus venosus also shrinks so all blood entering the liver passes through the sinusoids.

Question 16

Describe the APGAR score of newborns. (10)

Answer 16

A series of characteristics given a score from 0-2, 0 being nothing in that category, 2 being normal. 
Appearance (not blue 2)
Pulse (>100bpm 2)
Grimace (cough sneeze cry 2)
Activity (active movement 2)
Respiration (strong cry 2)

Question 17

Describe the 3 Ps of labour and why they’re important. (4)

Answer 17

Power - power of the myometrium to contract.
Passage - bony pelvis and soft tissues need to be big enough.
Passenger - size and presentation of foetus.
Failure to progress in labour may be due to an abnormality of one or more of these.