Intrapartum Science Flashcards
What is labour known as?
Parturition
How many stages of labour are there?
3
What are 2 considerations for the retrospective detection of labour?
- Cervical dilatation
- Cervical effacement
What are the 3 stages of labour?
Stage 1: Latent + active phase
Stage 2: propulsive + expulsive phase
Stage 3: Delivery of the placenta
What happens during stage 1 of labour?
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)
What happens during stage 2 of labour?
Stage 2 is from full cervical dilatation to delivery of the foetus. Is divided into:
1. Propulsive phase
2. Expulsive phase
What is considered a delay in the expulsive phase?
Delay is defined if the expulsive phase lasts >2hrs in nulliparous and >1 hour in multiparous women
What happens in the 3rd phase of labour?
Delivery of the placenta?
What is the curve of carus?
The angulation of the birth canal.
What is the mechanism of labour?
- 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
What happens during engagement?
- The transvers/oblique diameter of the fetal head enters the pelvic brim
- Asynclitism occurs prior to engagement
What are disorders of labour?
- Labour dystocia
- Breech presentation
- Shoulder dystocia
What are the 3 described patterns of labour dystocia?
- Prolonged latent phase
- Primary dysfunctional labour
- Secondary arrest
Key facts about prolonged latent phase
- Incidence: 3.5% in nulliparous women
- Relates to delayed cervical ripening
- Augmentation with oxytocin is not beneficial
Define primary dysfunctional labour
+ incidence?
- 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
Key facts about secondary arrest
- Incidence 6% in nulliparous women and 2% in multiparous women
- Usually linked with fetal malposition
Incidence of breech presentation
28 weeks = 30%
Term = 3%
Pregnancy related causes of breech presentation
- Increased parity
- Multiple pregnancy
- Prematurity
Fetal structural abnormality related causes of breech presentation
- Hydrocephalus
- myelomeningocoele
Fetal growth abnormality related causes of breech presentation
- FGR
- Oligohydramnios
- Polyhydramnios
Placental abnormality related causes of breech presentation
- Placenta praevia
- Short umbilical cord
Uterine abnormality related to breech presentation
- Bicornuate uterus
Pelvic abnormality related to breech presentation
Contracted pelvis
Types of breech
- Extended (or frank breech) = 60-70%
- Flexed (or complete breech)
- Footling
Fetal risks of vaginal breech delivery
- Intracranial haemorrhage
- Brachial plexus injury
- Limb fractures
- Spinal cord injury
Reasons for predominance of cephalic presentation
- Piriform shape of uterus
- Calcification of fetal skull (increased skull density).
What is shoulder dystocia?
Occurs when there is failure of the shoulders to deliver with gentle downwards traction on the fetal head.
Incidence of shoulder dystocia
0.6%
Which shoulder is commonly involved in shoulder dystocia?
Anterior shoulder
What are the signs of shoulder dystocia?
External rotation failure
Turtle necking
In shoulder dystocia how can fetal distress be caused?
Due to a reduction in oxygen supply caused by:
1. Uterine contraction
2. Fetal chest compression
What are fetal complications caused by shoulder dystocia?
Asphyxia
Brachial plexus injury
Fracture of clavicle (in 15%) and humerus (in 1%)
Brachial plexus injury
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
What are the risk factors of shoulder dystocia?
Fetal macrosomia
Maternal diabetes
Maternal obesity
Previous shoulder dystocia
Prolonged labour
Instrumental delivery
Percentage of shoulder dystocia in fetuses <4kg
48%
What percentage of shoulder dystocia is predicted by conventional risk factors?
15%
How many C sections need to be performed to prevent 1 permanent neurological injury from shoulder dystocia?
2300
What is the recurrence rate of shoulder dystocia?
15%
What is the rate of fetal pH dropping in shoulder dystocia?
0.04/min
