Normal labour Flashcards
Definition/Diagnostic criteria of true labour
- Regular, painful uterine contractions
- Increasing frequency and intensity
- Cervical effacement (shortening of cervix until indistinguishable from uterine wall)
- Progressive cervical dilatation (≥3cm is active)
- Descent of fetal presenting part in the pelvis
False labour
aka Braxton-Hicks’ contractions
- Irregular uterine contractions that are not of increasing frequency or intensity
- Last 4-8 weeks of pregnancy
- Normally painless, unpredictable and spontaneous
- Not a/w progressive cervical dilation or effacement
2nd stage of labour
From full dilatation to delivery of fetus
- primigravida: ~2h
- multigravida: ~1h
+ 1 hour if epidural given (no pressure from descending fetus -> passive descent of fetus, allow mom to regain sensation to push)
1st stage of labour
From onset of painful REGULAR uterine contractions to full dilatation of cervix (10cm)
- Divided into 2 phases: Latent vs Active
- Monitor descent of fetal head
3rd stage of labour
From delivery of the fetus to delivery of placenta
- Up to 30 mins in both nulli and multiparous women
Changes to mommy preceding labour
- False labour pains (braxton hicks)
- Lightening
- Fundal height drops a bit as baby drops into pelvis -> feels a bit easier to breathe - Discharge of mucus plug
- Cervical changes (effacement and dilatation)
- Show
- Can be blood-stained mucoid plug
What is ‘the show’ in labour?
Loosening and expulsion of the mucus plug that has been blocking the cervical canal during pregnancy
Duration of 1st stage of labour
Primigravida: 12h
Multigravida: 6h
1st stage of labour: Latent phase (variable)
- Effacement of cervix
- Dilatation of cervix from 0-3cm
1st stage of labour: Active phase (2-9h)
Rapid dilatation of cervix from 3-10cm with regular uterine contractions
-> Nulliparous women: 1cm/h
-> Multiparous women: 2cm/h
- Entire cervical length is retracted into LUS
- Ensure delivery 12h from now
*if uterus keeps contracting too much, this can cause uterine atony -> PPH -> rupture
If progress of cervical dilatation is <1cm/h for normal primiparous women, consider:
Uterine dysfunction
Fetal malposition
Cephalopelvic disproportion
Monitoring descent of fetal head
- Crichton’s method: Abdominal palpation - in “fifths”
- use pubic symphysis as landmark
- x/5 where x is the portion still above public symphysis and can be palpated - Vaginal examination: “Station” relates the level of the lowest point of fetal head with ischial spine
*Eg. 1cm above ischial spine is -1
What is LIE?
Relationship of longitudinal axis of the fetus to
the longitudinal axis of the mother
- longitudinal vs transverse vs oblique
What is PRESENTATION?
Part of the fetus directly overlying the pelvis
- cephalic vs breech vs shoulder
- cannot tell on abdo palpation
What is PRESENTING PART?
Part of the fetus that is
felt through the cervix on vaginal examination
- If baby is fully flexed, means baby is in cephalic presentation: first contact point is vertex
- If baby is fully extended, means baby is not in cephalic presentation: first contact point is face
What is POSITION?
An arbitrarily chosen portion of fetal presenting part described in relation to mother’s left/right, ant/posterior of birth canal
- For cephalic presentation with vertex as presenting part: use OCCIPUT as chosen point
Mechanics of labour - 3Ps
- Passage: Bony pelvis, soft tissue of the uterus (cervix and pelvic floor muscles)
- Powers: Uterine contraction
- Passenger: Fetus
If passenger is too large or passage is too small –> Cephalopelvic disproportion
Passage: Bony pelvis, soft tissue of the uterus (cervix and pelvic floor muscles)
- Gynaecoid pelvis (most common and best for vaginal delivery)
- Platypelloid and android pelvis (can cause obstructed labour)
If passenger is too large or passage is too small –> Cephalopelvic disproportion
Passenger: Fetus
Features that can affect labour
- Number of fetus
- Size
- Lie
-> Longitudinal: Normal vaginal delivery possible
-> Oblique, transverse: NVD not possible - Presentation
-> Cephalic: Vertex best presentation, NVD possible
-> Shoulder: NVD not possible
-> Breech: Attempt maneuvers, if not caesarian section preferred - Position
- Station
- Anomalies (eg. hydrocephalus, sacrococcygeal teratoma)
If passenger is too large or passage is too small –> Cephalopelvic disproportion
Powers: Uterine contraction
- dilate cervix
- push fetus through birth canal
- assessed by CTG or palpation of uterine fundus through maternal abdomen
- freq: 2-4/10 mins
- intensity increases over time
- duration ~20s in early labour and 40-90s in active phase
2’ power: Maternal effort
Mechanism of labour: 7 foetal cardinal movements in labour
- Engagement
- Descent
- Flexion
- Internal rotation
- Extension
- Restitution, External rotation
- Expulsion
Engagement
When the widest diameter of fetal presenting part is through the pelvic inlet
- Cephalic presentations: Biparietal
- Breech presentations: intertrochanteric
Based on the Crichton’s method, when the head is 3/5ths or more palpable = engaged!
Usually engages in L occiput anterior position
Descent
Downward passage of presenting part within maternal pelvis
Flexion
While descending through pelvis, fetal head meets resistance against pelvic floor muscles and shape of bony pelvis and will flex (fetal chin is touching fetal chest)
- functionally creates smallest sagittal diameter to pass through the maternal pelvis
