Intrapartum Science

Question 1

What is labour known as?

Answer 1

Parturition

Question 2

How many stages of labour are there?

Answer 2

3

Question 3

What are 2 considerations for the retrospective detection of labour?

Answer 3

1. Cervical dilatation
2. Cervical effacement

Question 4

What are the 3 stages of labour?

Answer 4

Stage 1: Latent + active phase
Stage 2: propulsive + expulsive phase
Stage 3: Delivery of the placenta

Question 5

What happens during stage 1 of labour?

Answer 5

Effacement and dilatation of the cervix up to full dilatation - 10 cm. Divided into:
- Latent phase (dilatation up to 4cm)
- Active phase (dilatation from 4cm onwards)

Question 6

What happens during stage 2 of labour?

Answer 6

Stage 2 is from full cervical dilatation to delivery of the foetus. Is divided into:
1. Propulsive phase
2. Expulsive phase

Question 7

What is considered a delay in the expulsive phase?

Answer 7

Delay is defined if the expulsive phase lasts >2hrs in nulliparous and >1 hour in multiparous women

Question 8

What happens in the 3rd phase of labour?

Answer 8

Delivery of the placenta?

Question 9

What is the curve of carus?

Answer 9

The angulation of the birth canal.

Question 10

What is the mechanism of labour?

Answer 10

• Engagement
• Descent of fetal head to below the ishcial spines and flexion
• Fetal head rotation to the occipito-anterior position, shoulders enter pelvis
• Extension and delivery of fetal head
• Restitution
• Delivery of shoulders and rest of body

Question 11

What happens during engagement?

Answer 11

1. The transvers/oblique diameter of the fetal head enters the pelvic brim
2. Asynclitism occurs prior to engagement

Question 12

What are disorders of labour?

Answer 12

1. Labour dystocia
2. Breech presentation
3. Shoulder dystocia

Question 13

What are the 3 described patterns of labour dystocia?

Answer 13

1. Prolonged latent phase
2. Primary dysfunctional labour
3. Secondary arrest

Question 14

Key facts about prolonged latent phase

Answer 14

• Incidence: 3.5% in nulliparous women
• Relates to delayed cervical ripening
• Augmentation with oxytocin is not beneficial

Question 15

Define primary dysfunctional labour
+ incidence?

Answer 15

• Is cervical dilatation slower than 1cm/hr during the active phase of stage 1 of labour
• Incidence = 26% in nulliparous women and 8% in multiparous women

Question 16

Key facts about secondary arrest

Answer 16

• Incidence 6% in nulliparous women and 2% in multiparous women
• Usually linked with fetal malposition

Question 17

Incidence of breech presentation

Answer 17

28 weeks = 30%
Term = 3%

Question 18

Pregnancy related causes of breech presentation

Answer 18

• Increased parity
• Multiple pregnancy
• Prematurity

Question 19

Fetal structural abnormality related causes of breech presentation

Answer 19

• Hydrocephalus
• myelomeningocoele

Question 20

Fetal growth abnormality related causes of breech presentation

Answer 20

• FGR
• Oligohydramnios
• Polyhydramnios

Question 21

Placental abnormality related causes of breech presentation

Answer 21

• Placenta praevia
• Short umbilical cord

Question 22

Uterine abnormality related to breech presentation

Answer 22

• Bicornuate uterus

Question 23

Pelvic abnormality related to breech presentation

Answer 23

Contracted pelvis

Question 24

Types of breech

Answer 24

1. Extended (or frank breech) = 60-70%
2. Flexed (or complete breech)
3. Footling

Question 25

Fetal risks of vaginal breech delivery

Answer 25

1. Intracranial haemorrhage 2. Brachial plexus injury 3. Limb fractures 4. Spinal cord injury

Question 26

Reasons for predominance of cephalic presentation

Answer 26

1. Piriform shape of uterus 2. Calcification of fetal skull (increased skull density).

Question 27

What is shoulder dystocia?

Answer 27

Occurs when there is failure of the shoulders to deliver with gentle downwards traction on the fetal head.

Question 28

Incidence of shoulder dystocia

Answer 28

0.6%

Question 29

Which shoulder is commonly involved in shoulder dystocia?

Answer 29

Anterior shoulder

Question 30

What are the signs of shoulder dystocia?

Answer 30

External rotation failure Turtle necking

Question 31

In shoulder dystocia how can fetal distress be caused?

Answer 31

Due to a reduction in oxygen supply caused by: 1. Uterine contraction 2. Fetal chest compression

Question 32

What are fetal complications caused by shoulder dystocia?

Answer 32

Asphyxia Brachial plexus injury Fracture of clavicle (in 15%) and humerus (in 1%)

Question 33

Brachial plexus injury

Answer 33

Occurs in 10% of shoulder dystocia Premanent neurological damage occurs in 10% of brachial plexus injury Caesarean section does not eliminate the risk of brachial plexus injury

Question 34

What are the risk factors of shoulder dystocia?

Answer 34

Fetal macrosomia Maternal diabetes Maternal obesity Previous shoulder dystocia Prolonged labour Instrumental delivery

Question 35

Percentage of shoulder dystocia in fetuses <4kg

Answer 35

48%

Question 36

What percentage of shoulder dystocia is predicted by conventional risk factors?

Answer 36

15%

Question 37

How many C sections need to be performed to prevent 1 permanent neurological injury from shoulder dystocia?

Answer 37

2300

Question 38

What is the recurrence rate of shoulder dystocia?

Answer 38

15%

Question 39

What is the rate of fetal pH dropping in shoulder dystocia?

Answer 39

0.04/min