Normal Labour + Delivery Flashcards
1
Q
What is the action of oestrogen and progesterone?
A
- Oestrogen - increases oxytocin receptors in uterus, also creates mucus plug to block cervix
- Progesterone - relaxes smooth muscles (inhibits uterine contraction during pregnancy)
- Near term progesterone levels fall and oestrogen stays the same which increases uterine contractions. This can cause false labour contractions aka Braxton Hicks contractions.
- Oestrogen and progesterone rapidly decline just before birth (partuition)
2
Q
What are the functions of hormones in the process of birth?
A
- Foetal stress stimulates corticotropin hormone release (ACTH)
- ACTH produced by anterior pituitary - causes cortisol release from adrenal gland
- Cortisol decreases progesterone and oestrogen production by the placenta and increases prostaglandin production by placenta
- Prostaglandin causes uterine contractions
- Baby pushing out triggers uterine/cervical stretch - stimulates sensory nerve fibres
- These nerves fibres stimulate oxytocin production from hypothalamus (in mother’s brain)
- Posterior pituitary releases oxytocin
- Oxytocin helps: uterine contraction, stimulates uterus to make more prostaglandins which causes further contractions (this process repeats)
3
Q
What does relaxin released from the placenta do?
A
- Loosens pelvic ligaments so pelvic bones can come apart slightly to support enlarging uterus
- Opens pelvic outlet by loosening pubic symphysis joint
- Dilates cervix in labour
4
Q
What happens in the latent phase of stage 1 of labour?
A
- Baby stretches cervix > sends signals to posterior pituitary and hypothalamus > oxytocin release
- Oxytocin stimulates uterine contractions
- Placenta releases prostaglandin > causes oxytocin release > contractions
- This positive feedback loop continues to open cervix
- Contractions come in waves in a regular rhythm and become stronger (painful contractions)
- This causes thinning of cervix > eventually cervix dilates to 3cm > active phase begins
- The thinning and widening (due to stretching) is called cervix effacement, relaxin also helps dilate cervix
- Mucus plug comes off and discharges from vagina - can occur a few days before true labour or during labour
5
Q
What happens in the active phase of stage 1 of labour?
A
- From ~4cm dilation of cervix
- Cervix continues dilating and contractions are regular and more painful
- Contractions create pressure > ruptures amniotic sac (SROM) - water has broken (usually clear)
- If water is green/smelly > this is meconium (first poo passed by foetus) > can be dangerous, as if foetus pooes into amniotic fluid it could swallow it and get into the lungs > meconium aspiration
- Cervix fully dilated once it reaches 10cm and mum will get the urge to push - can see crowning of babies head
- If baby’s body comes before head > breech position and usually delivered via C-section
6
Q
What happens in stage 2 of labour?
A
- Fetal head enters birth canal and ends with the birth of the newborn
- The uterus continues to rhythmically contract to push the baby out
- When head crowns turn baby to side to make rest of delivery easier
- Once baby is completely delivered the umbilical cord is cut
7
Q
What happens in stage 3 of labour?
A
- Can be physiological (mother does herself) or active management (AM) - doctor’s assist (less risk of active bleed)
- Contractions continue to deliver placenta (allows placenta to detach from uterus walls - place hand on fundus to apply pressure)
- Involution: uterus continues to contract to return it to normal size after placenta is delivered
- Mother can be given injection to stimulate uterine contractions to deliver placenta - syntocinon IM (synthetic version of oxytocin to stimulate contractions) or ergometrine (alternative)
- Must be delivered carefully as can cause haemorrhage (cut umbilical cord and control cord traction)
8
Q
What happens when breastfeeding occurs?
A
It leads to oxytocin secretion from posterior pituitary - causes uterine contraction to reduce bleeding, so ideally, women should breastfeed their child as soon as feasible post-delivery.
9
Q
What happens if the amniotic sac doesn’t rupture?
A
Sometimes during uterine contractions the amniotic sac doesn’t rupture - could be due to weak uterine contractions. The amniotic sac can be ruptured via inserting a hook.
- Don’t perform any vaginal examination until placenta praevia is ruled out, due to haemorrhage risk.
10
Q
What are contraindications for a hook to break the amniotic sac?
A
- Baby is in breech position
- Placenta praevia
11
Q
How long does labour take in nulliparous women?
A
- Initial stage: <20hr (if longer then failure to progress)
- Active stage: >1.2cm/hr
12
Q
How long does labour take in multiparous women?
A
- Initial stage: <14hrs
- Active stage: >1.5cm/hr (if this stage is slow, it’s called ‘primary dysfunctional labour’ but if after a normal period of active phase, the cervix stops dilating, this is ‘secondary arrest of labour’.
13
Q
What is the mechanism of labour?
A
- Baby descends (head first) towards pelvic inlet
- As baby’s head moves towards pelvic brim, it is on the left/right occipital position (OP) - this is so that the widest part of the head goes through the widest part of the pelvic inlet
- Then there’s flexion of the neck, this is so that the presenting diameter is suboccipital pragmatic (chin tuck to create a smaller structure)
- The baby rotates internally, so head is occipito-anterior and in an oblique position (babies facing towards the edge of the sacrum (where it meets iliac part) with the top of its head pointing towards the outside of the vagina)
- Then crowning occurs when head no longer moves back after contractions
- Delivery of head by extension - curve of the sacrum allows neck to extend and head to be delivered
- Internal rotation of the shoulders as they rotate in an anterior-posterior plane to fit through pelvic inlet (e.g. left shoulder adjacent to sacrum, right shoulder adjacent to pelvic brim)
- Head then rotates as well to be in line with the shoulders
- There is down retraction as anterior shoulder is delivered
- Lateral flexion as posterior shoulder delivered (upward traction) - baby is pulled up and away from perineum
14
Q
What are the fetal positions?
A
Longitudinal: - Breech - Cephalic - normal for VD (occipito-anterior, transverse, occipito-posterior) Transverse - right or left Oblique - right or left
15
Q
What are the stages of labour in simpler terms?
A
- Top of head moves towards cervix/pelvic inlet (engagement then descent)
- Neck flexion (flexion)
- Slight rotation to left/right so babies face towards sacrum (internal rotation)
- Head and neck pushed out (further descent, then extension)
- Baby rotates to the left/right so that one shoulder is facing towards belly button and the other towards mum’s buttocks (external rotation)
- Rest of body comes out (expulsion)
