22. Normal Birth

Question 1

initiation of labour

Answer 1

origin is unclear
multifactorial: hormonal, mechanical
foetal hypothalamus is triggered
maternal post pituitary releases oxytocin and decide releases prostaglandins

Question 2

physiology of labour initiation

Answer 2

increase in oestrogen (pro labour) and decrease in progesterone (pro pregnancy)
oxytocin and prostaglandins create uterine contractions
mechanical stimulation of uterus and cervix caused by over stretching and pressure

Question 3

stages of labour

Answer 3

latent phase
1st stage
2nd stage
3rd stage

Question 4

latent phase

Answer 4

effacement of cervix (shorts and thins)
contractions
intensity varies
preparation for labour: can last days

Question 5

diagnosing active labour

Answer 5

painful of active labour
effacement of cervix
dilatation of cervix to 4cm or more

Question 6

1st stage

Answer 6

active phase
established labour to full dilatation
vaginal examinations every 4 hours
average: 0.5cm per hour

Question 7

2nd stage

Answer 7

form full dilatation to delivery of the baby

Question 8

pelvic inlet

Answer 8

brim is oval, except where promontory projects

anteroposterior diameter = 12 cm

Question 9

pelvic outlet

Answer 9

diamond shaped 
3 diameters 
anteroposterior 
oblique
transverse

Question 10

fontanelles

Answer 10

anterior (bregma) 
- diamond shaped intersection of 4 sutures
- 2x3cm
- closes at 18 months 
posterior 
- Y shaped intersection of 3 sutures
closes at 6-8 weeks

Question 11

diameters of foetal skull

Answer 11

suboccipitobregmatic = 9.5cm - OA position
occipitofrontal = 11cm - OP position
supraoccipitomental = 13.5cm - brow
submentalbregmatic - 9.5cm - face

Question 12

mechanism of birth

Answer 12

head at pelvic brim, occipitotransverse position
flexion of neck
head descends and engages
head reaches pelvic floor, rotates to OA position
head delivers by extension
head ‘resititues’ - comes into line with shoulders
shoulders rotate into anterior/posterior diameter of pelvis
anterior shoulder delivered by lateral flexion
posterior shoulder by upward flexion

Question 13

3rd stage

Answer 13

delivery of placenta
normal blood loss = 300-500ml
inspection of placenta to ensure completion

Question 14

3rd stage active management

Answer 14

oxytocin given i.m. to maternal thigh
causes sustained uterine contractions
aids placental delivery
decreases risk of post parts haemorrhage

Question 15

3rd stage physiological management

Answer 15

mother naturally expels placenta and membranes with contractions

Question 16

foetal monitoring in labour

Answer 16

to detect foetal hypoxia and deliver baby if needed
intermittent auscultation
CTG
FBS

Question 17

intermittent auscultation

Answer 17

every 15 mins before and after contraction during 1st stage
every 5 mins in 2nd stage
any abnormality - use CTG

Question 18

cardiotocograph (CTG)

Answer 18

continuous print of foetal heart rate and contractions
abdominal ultrasound - detects cardiac movements, hence heart rate
clip applied to foetal scalp (FSE) - r-r wave of ECG

Question 19

foetal blood sampling (FBS)

Answer 19

used to check CTG findings

stab on foetal scalp, ph and base excess result