Labour + Birth Flashcards
What is labour?
The process by which the fetus + its supporting placenta and membranes pass from the uterus to the outside world
Three key processes in labour
- Regular high intensity contractions
- Softening + dilatation of the cervix
- Rupture of the fetal membranes
Timing of labour:
- miscarriage
- premature
- term
- miscarriage: <22 weeks
- premature: <37 weeks
- term labour: 37 weeks +
Timing of a miscarriage
Before 22 weeks
When is baby deemed premature?
Before 37 weeks
What is classified as term labour?
37 weeks +
What are the stages on labour?
- first stage: from the onset of regular uterine contractions until cervix is fully dilated 10cm
- second stage: from full dilatation until birth of fetus
- thirst stage: from birth of fetus until delivery of placenta + membranes
How is the birth canal created?
- softening of the pelvic ligaments
- increase in myometrial activity > contractions
- cervical dilatation + effacement
First stage of labour
From the onset of regular uterine contractions until cervix is full dilated
Second stage labour
From full dilatation until fetus is born
Third stage of labour
From birth of fetus until delivery of placenta + membranes
What is cervical ripening triggered by?
Prostaglandins
E2 + F2a
What is cervical ripening?
- marked reduction in collagen
- marked increase in glycoaminoglycans
- these both decease the aggregation of collagen fibres
- collagen bundles loosen
- influx of inflammatory cells + increase NO output
Movements of baby in labour
Engagement
Descent
Flexion
Internal rotation
Extension
External rotation (restitution)
Anterior shoulder delivery
Posteior shoulder delivery
What happens to the myometrium in pregnancy?
- becomes thicker
- due to increased cell size x10
- glycogen deposition
What hormones are involved in increases frequency + force of contractions inducing labour?
Prostaglandins
Oxytocin
Contractions in early pregnancy
Occur ~30 mins
Low amplitude
What are Braxton-Hicks contractions?
- Noticeable contractions later on in pregnancy
- Reduced frequency but increased amplitude
How do prostaglandins implement the change in contractions starting labour?
Enhancing release of calcium from intracellular stores > produces action potential
How do oxytocin implement the change in contractions starting labour?
Lowers threshold for triggering AP
Where is oxytocin secreted from?
Posterior pituitary gland
What is the Ferguson Reflux?
- brain stimulates posterior pituitary to release oxytocin
- causes smooth muscle lining of uterus to contract
- baby pushes against cervix > stretch
- stretching causes nerve implases to be sent to brain
- process repeats
What is brachystasis?
Myometrial cells contract and shorten, but do not regain their original length upon relaxation > shortness uterus progressively
What is effacement of the cervix?
Thinning of cervix
What is full dilatation of cervix?
10cm
Duration of second stage of labour
1 hour
2 hours in first pregnancies
What is the physiological third stage of labour?
- no medication used
- midwife waits for umbilical cord to stop pulsating before it is cut + delivery of placenta occurs passively
What is the active third stage of labour?
- oxytocin or ergometrine injection given
- causes contraction of uterus
Why is active management of the third stage of labour recommended for all women?
Reduces risk of post partum haemorrhage
What are the three Ps affecting labour?
Passage
Passenger
Powers (contractions)
What is the diameter of the birth canal?
11cm max
Limited by the pelvis
What are the three ways a baby can lie in the uterus before delivery?
Longitudinal lie (most common)
Transverse lie
Oblique lie (unstable)
Types of fetal presentation
- Cephalic (head first)
- Breech (bum/feet first)
Types of breech fetal presentation
- Complete breech
- Frank breech (bum first, feet up by head)
- Footling breech (feet first)
Types of cephalic presentation
- vertex (well flexed head) | normal
- vertex (deflexed head)
- brow
- face
How do you determine fetal position?
Vaginal exam
Obstetric abdominal exam
Does a high or low apgar score mean a baby is healthy?
Low apgar score
What is shoulder dystocia?
Vaginal Cephalic delivery that requires additional obstetric manoeuvres to deliver the fetus after the head has delivered + gentle traction has failed + shoulder is stuck
Complications of shoulder dystocia
- Erb’s palsy
- neurological dysfunction
- neonatal mortality
- PPH
- tears
Risk factors of shoulder dystocia
- previous shoulder dystocia
- macrosomia
- diabetes mellitus
- maternal BMI >30
- prolonged labour
- assisted vaginal delivery
Types of intra partum monitoring
- intermittent monitoring: Doppler stethoscope
- continuous electronic fetal monitoring: Cardiotocography + fetal scalp electrode
- fetal blood sampling
What are the indications of assisted delivery?
- failure to progress
- maternal exhaustion
- fetal compromise in 2nd stage
Types of assisted delivery
Forceps
Suction cup
What are the indications of C section
- malpresentation
- macrosomia
- failure to progress
- fetal compromise
- previous C section
- fetal malformation
- multiple pregnancies
Outline an induced labour
- prostaglandins vaginal
- IV oxytocin
- artificial rupture of membranes
