Normal(ish) Labour Flashcards
What factors determine progress during labour?
Degree of force expelling fetus (the powers)
Dimensions of pelvis and resistance of soft tissues (the passage)
Diameters of fetal head (the passenger)
What happens during contractions?
Uterus contracts for 45-60 secs every 2-3 minutes
Cervix pulls up (effacement) and dilates
Poor uterine activity is common in nulliparous women
What are the measurements of the bony pelvis?
Inlet = transverse>AP
- transverse 13cm
- AP 11cm
Mid-cavity = round
- transverse and AP are equal
Outlet = AP>transverse
- transverse 11cm
- AP 12.5cm
What are the main differences of primips?
Inefficient uterine action -> long labour
Functional capacity of pelvis not known - possibility of cephalopelvic disproportion
Serious injury to child more common
Uterus virtually immune to rupture
How does the uterus change during pregnancy?
Smooth muscle fibres undergo hypertrophy and hyperplasia
Contracts intermittently from beginning of pregnancy, frequency and amplitude increases - most intense at fundus
What are pro-pregnancy factors?
Progesterone - produced from corpus luteum for 8 weeks and then placenta
Nitric oxide
Catecholamines
Relaxin
What effect does progesterone have on labour?
Decreases uterine oxytocin receptor sensitivity
Promotes uterine smooth muscle relaxation
What is Mifepristone?
Progesterone antagonist
Increases myometrial contractility
What are pro-labour factors?
Oestrogens Oxytocin Prostaglandins Prostaglandin dehydrogenase Inflammatory mediators
What is the role of oxytocin?
Nonapeptide
Produced by posterior pituitary
Stimulates uterine contractility
Doesn’t increase towards labour
What is the role of oestrogens?
Increase at labour - placenta secretes corticotrophin-releasing hormone
Increase oxytocin receptor expression in uterus
What is the role of prostaglandins?
Double around labour Synthesised from arachidonic acid by COX enzymes in fetal membrane Promote cervical ripening Stimulate uterine contractility Upregulate oxytocin receptors
How is labour diagnosed?
Painful regular contractions -> effacement and dilation of cervix
Accompanied by show (white/pink mucus plug from cervix) +/- rupture of membranes
What is the first stage of labour?
From diagnosis to 10cm dilation of cervix
Latent phase - first 3cm take several hours
Irregular contractions, may last 8hrs+ in primips
Active phase - 3-10cm Contractions are regular, rhythmic and painful 3-4:10 mins Last 1 mins 12-14hrs in primips
What is the second stage of labour?
From full dilation to delivery
Passive stage - until head reaches pelvic floor and woman experiences desire to push
Compression of fetal head and placenta -> vagal response -> transient fall in fetal heart rate
Active stage - pressure of head on pelvic floor produces desire to push
40 mins for nulliparous, 20 mins for multiparous
What is the third stage of labour?
From delivery of fetus to delivery of placenta
Lasts around 15 mins and can cause blood loss of 500ml
Uterine muscle fibres contract to compress blood vessels
How much blood is lost during delivery of the placenta?
Around 500ml
How is the perineum damaged during delivery?
Damaged in 2/3 of nulliparous and half of multiparous women
1st degree - minor damage to fourchette
2nd degree/episiotomy - perineal muscle
3rd degree - anal sphincter
4th degree - anal mucosa
How does the fetus move during the 1st stage of labour?
Flexed head as it descends
90 degree rotation from OT to OA/OP position
How does the fetus move during the 3rd stage of labour?
Head extends as it is delivered over perineum
Rotates back to transverse before shoulders deliver
What is the station of a fetus?
Descent of head of vaginal palpation
Measured in relation to ischial spines
-3 is above spines
+3 is below spines
What causes the cervix to efface?
Prostaglandins and glycoproteins weaken collagen fibres of cervix
What is vertex presentation and what is felt?
Maximum flexion with bowed head
Presenting diameter of 9.5cm
Anterior fontanelle (bregma) Sagittal, coronal and lamboidal suture Posterior fontanelle (occiput)
What is brow presentation and what is felt?
Extension of 90 degrees
13cm diameter
Forehead of fetus
Anterior fontanelle (bregma)
Sagittal and coronal suture
What is face presentation and what is felt?
Hyperextension of 120 degrees
Face
Part of anterior fontanelle
What is the attitude of the fetus?
The relationship between fetal head and spine i.e. flexed, extended
What is the position of the fetus?
Relationship of presenting part to maternal pelvis
Must rotate at outlet so sagittal suture lies vertical
Usually occiputo-anterior
Occipito-posterior may cause difficulties
Occipito-transverse means delivery without assistance is impossible
What is Ferguson’s reflex?
Descent of presenting part in pelvis Pressure of presenting part on cervix Afferent impulse to hypothalamus Efferent impulses to post pituitary Post pituitary releases oxytocin Stimulation of contractions in uterus Increases pressure on cervix
How do contractions occur?
Mechanical stretching of uterus stimulates myometrium to make it more responsive
Contractions begin in fundus
Axis of uterus straightens, promotes descent of presenting part
What observations are done during labour?
Frequency of contractions - 30 mins BP and vaginal examination - 1 hour Pulse - 15 mins Temp - 4 hours FHR - 5 mins, after contractions
What is the relevance of meconium stained liquor?
Sign of fetal distress and risk of meconium aspiration
How is delay in first stage of labour managed?
Artificial rupture of membranes then reassessment after 2 hours
IV syntocinon then continuous electronic fetal monitoring
REDUCE if >5 contractions/10 mins
STOP if pathological CTG, fresh vaginal bleeding or emergency LSCS
What is classified as delay in first stage of labour?
Cervical dilatation less than 1cm/hour after 3cm
What dose of Syntocinon is used?
10 units in 500ml saline
Infuse at 3ml/hr
No more than 36ml/hr for multiparous women
In patients at risk of fluid overload (pre-eclampsia, diabetes, cardiac disease) - make up with 50ml saline
What fetal risk factors are associated with poor outcomes?
Presence of meconium
Maternal pyrexia
CTG abnormalities
What maternal risk factors are associated with poor outcomes?
Malposition -> increased perineal trauma
PPH more common in women with long second stage
When is continuous fetal monitoring recommended?
Fetal heart baseline 160bpm Deceleration of the fetal heart Oxytocic augmentation Epidural analgesia Maternal pyrexia, vaginal bleeding, passage of meconium Active stage >60 mins
What are features of uterine dehiscence and rupture?
Abdo pain (constant) Tachycardia Vaginal bleeding Haematuria Collapse Fetal bradycardia or decelerations
How are epidurals managed during second stage?
Associated with increased length of second stage and risk of instrumental delivery
No increase in rate of CS
0.1% bupivacaine with fentanyl
Use syntocinon to reduce risk of instrument delivery
Is syntocinon used in multiparous women regularly?
NO
What is pudendal nerve block?
Injection of lidocaine into perineum before episiotomy
How much numbness does the pudendal nerve block give?
Doesn’t stop:
- sensation to ant portion of perineum (ilioinguinal and genitofemoral nerves)
- uterine contraction pains and cervical dilation (T10-L2)
What needle is used for pudendal nerve block?
Iowa trumpet or Kobak
with 6 inch needle
What positions are best to deliver in?
Squatting
Kneeling
Left-lateral
Not flat on back as this compresses blood vessels, reduces cardiac output and causes hypotension
What is pyrexia in labour and what is the significance?
> 37.5
Associated with increased risk of neonatal illness
More common with epidural and prolonged labour
Cultures of vagina, urine and blood are taken
Paracetamol given
Abx if fever reaches 38 or other signs of sepsis
How is slow progress of 1st stage of labour treated in nullips?
First amniotomy
Wait 1-2 hours and if cervical dilation isn’t furthered then oxytocin
Increases dilatation within 4 hours if it’s going to be effective
What are causes of hyperactive uterine activity?
Placental abruption
Too much oxytocin
Prostaglandin administration
Excessively strong/frequent/prolonged contractions
Fetal distress as placental blood flow is diminished
Tx: tocolyitc (salbutamol)
C-section
How is slow progress of 2nd stage treated in nullips?
Passive stage - oxytocin started and pushing delayed for 2 hours
Active stage - if >1hr, spontaneous delivery unlikely due to maternal exhaustion
Episiotomy or ventous/forceps
How are OP positions managed during labour?
Longer and more painful labour
Many rotate to OA spontaneously
May require C-section or ventouse manual rotation
How are OT positions managed during labour?
Only significant after 1hr of pushing in 2nd stage
Ventouse to rotate with traction
What presentations require C-section?
Brow presentation
Face presentation with chin posterior
What is cephalo-pelvic disproportion and who does it occur in?
Retrospective diagnosis
Large babies
Short women
Head remains high in nulliparous women
What is the gynaecoid pelvis?
50-80% Caucasian women
Ideal pelvis
What is the anthropod pelvis?
Narrower inlet
Transverse less than AP
What is the android pelvis?
Heart shaped inlet
Funnels down to mid-pelvis
What is the platpelloid pelvis?
Oval shape of inlet persists in mid pelvis
What causes abnormal pelvic architecture?
Rickets Osteomalacia Poorly healed pelvic fractures Kyphosis/scoliosis Poliomyelitis Congenital malformations
Ovarian tumour
Uterine fibroid
What causes damage to the fetus during birth?
Fetal hypoxia - distress Infection/inflammation Meconium aspiration -> chemical pneumonitis Trauma - forceps Fetal blood loss
What pH indicates significant hypoxia?
pH less than 7.2 in FBS
What causes hypoxia in labour?
Contractions reduce placental perfusion and compress umbilical cord Placental abruption Hypertonic uterine state Use of oxytocin Prolapse of umbilical cord Maternal hypotension
What is meconium seen in the amniotic fluid?
Rare in preterm
Common after 41 weeks
Peasoup meconium increases mortality 4x
How is fetal distress managed?
Intermittent auscultation of fetal heart - if abnormal or meconium or long labour then
Continuous CTG - sustained bradycardia -> deliver
FBS - if abnormal and >7.2 then repeat after 30 mins
DELIVER
What resuscitative measures are taken for fetal distress before FBS and delivery?
Woman placed in left lateral position - avoid aortovacal compression
Oxygen and IV fluids
Stop oxytoicin, stop contractions with beta-2 agonists
VE - exclude cord prolapse and very rapid progress
How is perinatal infection treated?
Screen for organism and treat high risk groups
Low grade maternal fever - RF for seizures, fetal death and cerebral palsy
How is meconium aspiration reduced?
Amniofusion of saline into uterus
