L22 Pregnancy and Birth Flashcards
Initiation of labour overview
Remains uncertain
Multifactorial in origin
- hormonal
- mechanical
Foetal hypothalamus is triggered
Maternal post pituitary releases oxytocin
Decidua releases prostaglandins
Initiation of labour (hormones)
Increase in oestrogen pro-labour hormone
Decrease in progesterone pro-pregnancy hormone
Release of oxytocin by the mother’s posterior pituitary gland
Prostaglandins from the decidua
Together creating uterine contractions
Mechanical stimulation of the uterus and cervix caused by overstitching and pressure from the posterior pituitary
Stages of labour
Latent phase
1st stage of labour
2nd stage of labour
3rd stage of labour
Latent phase of labour
Effacement of cervix
Contractions
Intensity varies
Effacement of the cervix
Before labour 0% effacement
Early effacement 30%
Complete effacement 100%
Complete dilation
Diagnosis of active labour
Painful regular contractions
Cervical effacement
Dilation of the cervix of 4cms or more
Active labour/first stage of labour
Established labour to full cervical dilation
Vaginal examinations
Average is 0.5cm/hour
Descent of the foetal head in relation to the ischial spines
Progress measured by dilatation and descent of the foetal head (in relation to the pelvic brim and ischial spines)
Second stage of labour
From full dilatation to the delivery of the baby
Pelvic inlet
The brim is oval except where the promontory projects
The anteroposterior diameter is 12cm
Pelvic outlet
The outlet is diamond shaped
Its 3 diameters are:
- anteroposterior (as the coccyx is deflected backwards this is the space available during birth)
- oblique
- transverse
Fontanelles
Anterior fontanelle (bregma)
- diamond shaped intersection of 4 sutures
- 2x3cms
- closes at 18 months
Posterior fontanelle
- Y shaped intersection of 3 sutures
- closes at 6-8 weeks
Diameters of the foetal skull
Suboccipitobregmatic (9.5 cms) = OA position
Occipitofrontal (11 cms) = OP position
Supraoccipitomental (13.5 cms) = brow
Submentalbregmatic (9.5 cms) = face
Mechanism of birth
Head at pelvic brim Occipital transverse (OT) position
Flexion of neck (suboccipitobregmatic)
Head descends and engages
Head reached pelvic floor - rotates to occipital anterior
Head delivers by extension
Head ‘restitutes’ (comes in line with shoulders)
Shoulders rotate into anterior/posterior diameter of pelvis
Anterior shoulder delivered by lateral flexion from downward pressure on baby’s head
Posterior shoulder by upward lateral flexion
Third stage of labour
Delivery of placenta
Normal estimated blood loss 300-500mls
Inspection of placenta to ensure complication
2 methods in third stage of labour
- Active management (CTT)
Oxytocin i.m. given into maternal thigh
-cause sustained uterine contraction
-aids delivery of the placenta and contraction of the placental bed
-decreases risk of post part haemorrhage (PPH) - Physiological: mother naturally expels the placenta and membranes with contractions
Foetal monitoring in labour
To detect foetal hypoxia and deliver baby if needed
Screening the foetal heart rate by
- intermittent auscultation by Pinard or Sonicaid
- CTG (cardiotocograph)
- FBS
Intermittent auscultation
Every 15 mins before and after a contraction during the first stage
Every 5 mins in the second stage
Any abnormality heard would lead to the use of CTG
Cardiotograph
Continuous print out of the foetal heart rate and contractions
-abdominal ultrason
=>detects cardiac movements and hence HR
-a clip applied to the foetal scalp (FSE)
=>detects the R-R wave of the foetal ECG
Most usual is the abdominal ultrasound
Foetal Blood Sampling
CTG is highly sensitive e.g. if normal, baby is ok
But poorly specific e.g. if abnormal only a few babies are hypoxic
Use of CTG less to a 4 fold increase in Caesareans Sections for foetal distress THEREFORE need to check the CTG findings with FBS
How FBS is done
Stab on the foetal scalp
Blood collected via a glass pipette
pH and base excess result
Contraindications of FBS
Infection such as HIV, Hepatitis B
Foetal bleeding disorder
Prematurity less than 32 weeks
