T2 L22 Pregnancy and birth Flashcards
How is labour initiated?
Remains uncertain
Multifactorial in origin - hormonal and mechanical
Describe how labour initiation is mechanical?
Stimulation of uterus and cervix caused by overstitching and pressure
What happens during the initiation of labour?
Foetal hypothalamus is triggered Maternal posterior pituitary releases oxytocin Decidua releases prostaglandins Increase in oestrogen Decrease in progesterone
What are the stages of labour?
Latent phase
1st stage
2nd stage
3rd stage
What happens in the latent phase of labour?
Effacement of cervix
Contractions
Intensity varies
What is effacement?
Cervix softens, shortens and thins
Describe the stages of effacement of the cervix during labour
Before labour - 0% effacement
Early effacement - 30%
Complete effacement -100%
Complete dilatation
What happens during the first stage of labour?
Duration from established labour to full cervical dilation
Vaginal examinations carried out every 4 hours
Descent of foetal head in relation to ischial spine
What is the rate of cervical dilation if this is their first baby?
0.5 cm per hour
How is labour diagnosed?
Painful, regular contractions
Cervical effacement
Dilation of cervix of 4cms or more
What is the second stage of labour?
Duration from full dilation to delivery of the baby
Describe the mechanism of birth
1) Head at pelvic brim in OT position
2) Flexion of neck
3) Head descends and engages
4) Head reaches pelvic floor and rotates to OA position
5) Head delivers by extension
6) Head restitutes
7) Shoulders rotate into anterior / posterior diameter of pelvis
8) Anterior shoulder delivered by lateral flexion from downward pressure on baby’s head
9) Posterior shoulder delivered by upward lateral flexion
What happens in the 3rd stage of labour?
Delivery of the placenta
What are the 2 methods of delivering the placenta?
Active management
Physiological
How is the placenta delivered by active management?
Oxytocin given I.M. into maternal thigh
Causes sustained uterine contraction
Aids delivery of the placenta and contraction of the placental bed
Decreases risk of postpartum haemorrhage
How is the placenta delivered physiologically?
Mother naturally expels placenta and membranes with contractions
Usually occurs within 1 hour
Encourage mother to breastfeed as this releases oxytocin which aids contractions
What is the estimated blood loss?
300-500mls
What is the anteroposterior diameter of the pelvis?
12cm
What are the 3 diabetes of the pelvic outlet?
Anteroposterior - coccyx is deflected backwards to provide space for birth
Oblique
Transverse
Describe the anterior fontanelle
Bregma
Diamond-shaped intersection of 4 sutures
2 x 3cms
Closes at 18 months
Describe the posterior fontanelle
Y-shaped intersection of 3 sutures
Closes at 6-8 weeks
What is the diameter and delivery position of the suboccipitobregmatic?
9.5cms
OA position
What is the diameter and delivery position of the occipitofrontal?
11cms
OP position
What is the diameter and delivery position of the supraoccipitomental?
13.5cms
Brow position
What is the diameter and delivery position of the submentalbregmatic?
9.5cms
Face position
Why is foetal monitoring in labour important?
To detect foetal hypoxia and deliver baby if needed
How can we screen foetal heart rate?
Intermittent auscultation by pinard or sonicaid
CTG
FBS
How often is intermittent auscultation carried out?
Every 15 minutes after a contraction during 1st stage of labour
Every 5 minutes in the second stage
What happens if an abnormality is heard on intermittent auscultation?
CTG is used
What is a CTG?
Cardiotocograph
Continuous print out of foetal heart rate and contractions
Abdominal ultrasound
FSE
What is FSE?
Clip applied to foetal scalp
Detects R-R wave of foetal ECG
What is FBS?
Foetal blood sampling
Stab on foetal scalp, collect blood in glass pipette
pH and base excess result
When is FBS contraindicated?
Infections e.g. HIV or hep B
Foetal bleeding disorder
Prematurity below 32 weeks
When should FBS used instead of CTG?
CTG is highly sensitive but poorly specific
Using CTG leads to 4 fold increase in C-sections for foetal distress so need to check CTG findings with FBS
