Mechanism of Labour

Question 1

What are the main stages of Labour?

Answer 1

Latent
First Stage
Second Stage
Third Stage

Question 2

What occurs in the Latent phase of Labour?

Answer 2

Irregular contractions
Mucoid plug
Cervical effacement and dilation (0-4cm)
2-3 days

Question 3

What occurs in the first stage of Labour?

Answer 3

Increased regular Uterine contractions, cervix effacement and dilate up to 10cm

Question 4

What happens in the Second stage?

Answer 4

Full dilatation and birth of foetus

Question 5

What happens in the Third stage of Labour?

Answer 5

Foetal Birth –> Placental expulsion
Give drugs to reduce PPH (Syntometrine)

Question 6

What are the main hormones of Labour?

Answer 6

Oxytocin (Prostaglandin)
Oestrogen (Prolactin)
Beta Endorphin
Adrenaline

Question 7

How does each hormone of Labour functionL

Answer 7

1) Oxytocin: Contractions following urge
Prostaglandin: Aid with cervical ripening
2) Oestrogen: Inhibit progesterone at onset of labour
Prolactin: Mammary gland milk prod
3) Beta Endorphins: Natural pain relief
4) Adrenaline: Released at birth for energy to give birth

Question 8

What are the 3 foetal birth positions?

Answer 8

1) Cephalic: Head first, 90% of time
2) Breach: Feet first
3) Transverse: Longitudinal

Question 9

What is the physiological mechanism of contractions?

Answer 9

1) Contract from the Fundus
2) Shortening of Muscle Fibres
3) Labour progress with increased amplitude of cont.
4) Foetus face down with increased central pressure

Question 10

What are the features of the Gynaecoid pelvis?

Answer 10

1) Inlet is slightly transverse oval
2) Sacrum wide with average concavity and inclination
3) Side walls straight with blunt ischial sides
4) Wide subpubic arch

Question 11

What are the main landmarks of the foetal skull?

Answer 11

Anterior Fontanelle
Coronal suture
Sagittal suture
Posterior Fontanelle
Lamboid Suture

Question 12

What are the main mechanisms of Labour?

Answer 12

1) Descent: Foetus desc. into pelvis by ^ cont and M tone
2) Flexion: Uterine contractions exert Pa down foetal spine, causing felxion and foetal head circumference reduces
3) Internal Rotation: Each contraction rotates FH to pelvic floor
4) Extension: FH occiput slips under SupraPubic arch and head can extend, with head born
5) Restitution: Foetus aligns FH with shoulders, causing turning
6) External Rotation: FH rotates to face right or left medial thigh of mother
7) Delivery of Body: Gentle downward contraction conducted by midwife to assist delivery of shoulder below suprapubic arch

Question 13

What are the associated benefits of Delayed Cord Clamping?

Answer 13

1) Allows baby to receive increased Hb, RBC, iron, stem cells
2) Gives baby more time to transition to extra uterine life
3) Reduced need for inotropic suport

Question 14

What are the Pros and Cons of Hands-Off Non-Invasive Analgesia (Water Birth)

Answer 14

Pros: No risk to baby, partner can help facilitate and non invasive
Cons: Birthing pool might not be available
Some will work better than others

Question 15

What are the Pros and Cons of Entonox?

Answer 15

Pros: Fast acting, Used alongside other analgesia, no need for foetal monitoring and Paracetamol can be accessed
Cons: Make women nauseous and light headed, effect will wear off quickly

Question 16

What are the Pros and Cons of Opioids?

Answer 16

P: No delay as administered by midwife, can mobilise, doesn’t slow down labour and make woman drowsy so sleep between contractions
C: N&V, Remifentanyl only by Anaesthetist, Cause R depression in both mother and foetus

Question 17

What are the Pros and Cons of Epidural?

Answer 17

Pros: Total pain relief in 90% and effect lasts until baby is born
Cons: Reduced mobility, take an hour to work, need a urinary catheter, slow down labour if not established