Labour and birth Flashcards

1
Q

Define labour

A
  • Process by which foetus and supporting placenta pass from uterus to outside world
  • Regular uterine contractions result in thinning and dilation of cervix
  • Allows products of conception to leave uterus
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2
Q

What are the 3 key processes of labour?

A
  • Regular high intensity contractions
  • Softening and dilation of cervix
  • Rupture of foetal membranes
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3
Q

What triggers labour?

A
  • Mechanical
  • Hormonal
  • Prostaglandins
  • Neurological
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4
Q

What is labour called at different stages of pregnancy?

A
  • If expulsion of foetus and placenta occurs after 24 weeks of gestation = labour
  • Before 24 weeks = miscarriage/parturition
  • Labour that occurs before 37 weeks of gestation = premature/preterm labour
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5
Q

What are the 3 stages of labour?

A
  1. From onset of established labour (regular uterine contractions) until cervix is fully dilated
  2. From full dilation until foetus is born
  3. From birth of foetus until placenta and membranes are delivered
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6
Q

Outline what happens in the first stage of labour

A
  • Creation of birth canal
  • Release of structures which normally retain foetus in uterus
  • Enlargement and realignment of cervix and vagina
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7
Q

Outline what happens in the second stage of labour

A
  • Expulsion of foetus
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8
Q

Outline what happens in the third stage of labour

A
  • Expulsion of placenta
  • Changes to minimise blood loss from mother
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9
Q

What are the different phases of the first stage of labour?

A
  • Latent phase (uterus prepares to contract)
  • Active phase - consists of acceleration phase, phase of maximum slope, deceleration phase
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10
Q

What does the clinical management of labour crucially depend on?

A
  • Lie, presentation and position of foetus
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11
Q

What is meant by the lie of the foetus?

A
  • Relationship of long axis of foetus to long axis of uterus
  • Commonest lie is longitudinal with head or buttocks posterior
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12
Q

What is meant by the presentation of the foetus?

A
  • What part of foetus is adjacent to pelvic inlet
  • If baby lies longitudinally, presenting part may be head (cephalic) or breech (podalic)
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13
Q

What happens if the baby is lying transversely?

A
  • Can’t be delivered vaginally
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14
Q

What is the presenting part of the foetus?

A
  • Portion of foetal body that is either foremost in birth canal or in closest proximity to it
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15
Q

How do we determine foetal position?

A
  • Obstetric examination - can feel curvature of spine and determine where baby’s head is
  • Vaginal examination - can palpate baby’s head and feel suture lines to work out which way baby is facing
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16
Q

What are the different types of breech position?

A
  • Complete breech - legs crossed
  • Frank breech - legs extended up
  • Footling breech - dangerous because foot can come out before cervix is fully dilated and lead to cord prolapse
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17
Q

What determines the limits of the birth canal?

A
  • Pelvis
  • Diameter is 11cm max
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18
Q

What allows the creation of the birth canal?

A
  • Softening of pelvic ligaments may allow some expansion
  • Increase in myometrial activity (contractions)
  • Cervical dilation and effacement
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19
Q

What must happen to the cervix to create a birth canal?

A
  • Dilate - facilitated by structural changes called cervical ripening
  • Produced by forceful contractions of uterine smooth muscle
  • First thin cervix (effacement) and then dilate it
  • Retracted anteriorly
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20
Q

What changes occur at a cellular level to allow cervical ripening?

A
  • Cervix has high connective tissue content made up of collagen fibres embedded in a proteoglycan matrix
  • Ripening involves marked reduction in collagens
  • Plus marked increase in glycosaminoglycans
  • Causes collagen bundles to loosen
  • Influx of inflammatory cells
  • Increased nitric oxide output
  • Triggered by prostaglandins (E2 and F2a)
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21
Q

What happens to the myometrium during pregnancy?

A
  • Myometrium gets much thicker
  • Due to increased cell size (x10) and glycogen deposition
22
Q

What happens to cause contractions?

A
  • Intracellular apparatus of myometrium containing actin and myosin generates force
  • Triggered by a rise in intracellular Ca2+ concentration
  • Produced by action potentials in cell membrane
  • Stimulated by oxytocin
23
Q

What are contractions like before labour begins?

A
  • May occur every 30 minutes in early pregnancy
  • Low amplitude
  • Frequency falls as pregnancy continues with some increase in amplitude
  • Braxton-Hicks contractions
  • None of these are forceful enough to have any effect on cervix
24
Q

How do prostaglandins act?

A
  • Enhance release of calcium from intracellular stores
25
Q

How does oxytocin act?

A
  • Peptide hormone
  • Secreted from posterior pituitary gland
  • Under control of neurones in hypothalamus
  • Lowers threshold for triggering action potentials
26
Q

Outline the Ferguson Reflex

A
  1. Stronger uterine contractions push baby’s head against cervix
  2. Baby’s head pushes on cervix, causing it to stretch
  3. Nerve impulses from cervix relayed to brain
  4. Pituitary gland stimulated to release oxytocin
  5. Uterine contractions become stronger due to increased oxytocin concentration
27
Q

What is brachytasis?

A
  • At each contraction, muscle fibres shorten but do not relax fully
  • Occurs in uterine smooth muscle during labour
  • Shortens uterus progressively
  • Helps push presenting part into birth canal
28
Q

When does the first stage of labour end?

A
  • When cervical dilation reaches 10 cm
  • 2nd stage normally lasts 1-2 hours
29
Q

Outline what happens in the second stage of labour?

A
  1. Descended head flexes as it meets pelvic floor, reducing diameter of presentation
  2. Internal rotation
  3. Sharply flexed head descends to vulva, stretching vagina and perineum
  4. Head is then delivered (crowning)
  5. Head rotates back to original position and extends
  6. Shoulders then rotate, followed by head
  7. Shoulders deliver
  8. Rest of foetus rapidly delivers
30
Q

What is meant by a physiological third stage of labour?

A
  • Women who have had uncomplicated pregnancy and labour
  • Do not receive any oxytocic drugs
  • Attendant waits for umbilical to stop pulsating, then cuts it
  • Delivery of placenta occurs passively
31
Q

What happens to the third stage of labour in women who cannot have a physiological placental delivery?

A
  • Active management is advised
  • Syntocinon (oxytocin) is given to stimulate uterus to contract
  • Done in situations where there is increased risk of post partum haemorrhage or depending on parental choice
32
Q

Other than to deliver the foetus and placenta, what is the function of the contracting uterus?

A
  • Compresses blood vessels and reduces bleeding
  • Often enhanced by administration of an oxytocic drug
33
Q

Why must the placenta and membranes be checked to ensure they are complete?

A
  • Common cause of post partum haemorrhage
34
Q

What does APGAR stand for?

A
  • Appearance (pink, pale, blue)
  • Pulse
  • Grimace (crying)
  • Activity (movement)
  • Respiration (crying)
35
Q

What are the factors affecting labour?

A
  • Passage (birth canal)
  • Passenger (foetus)
  • Powers (contractions)
36
Q

What can affect the passage of the foetus?

A
  • Pelvis might be too small
  • Cephalopelvic disproportion (baby might be too large or pelvis too small)
37
Q

What happens to a baby’s head during birth?

A
  • Moulding
  • Skull bones aren’t fused and can overlap
  • External compressive forces can change foetal head shape
  • Reduces diameter
38
Q

Define shoulder dystocia

A
  • Vaginal cephalic delivery that requires additional obstetric manoeuvres to deliver foetus after head has delivered and gentle traction has failed
39
Q

When does shoulder dystocia occur?

A
  • When either anterior (or less commonly posterior) foetal shoulder impacts on maternal symphysis or sacral promontory respectively
40
Q

What are the complications of shoulder dystocia?

A
  • Brachial plexus injury (Erb’s palsy)
  • Neurological dystfunction/disability
  • Neonatal mortality
  • PPH
  • Tears
41
Q

What are some risk factors for shoulder dystocia?

A
  • Macrosomia
  • Diabetes
  • Obesity
  • Previous dystocia
42
Q

Outline Braxton Hicks contractions

A
  • Intensity of 10-15 mmHg
  • Last 30 seconds
  • Once per hour
  • Do not change cervix
43
Q

What kind of contractions occur before onset of labour?

A
  • Intensity of 20-30 mmHg
  • Intervals of 5-10 minutes
  • About 48 hours prior to onset of labour
44
Q

What kind of contractions occur during the first phase of labour?

A
  • Intensity of 20-30mmHg
  • 2-4 contractions every 10 minutes
45
Q

What kind of contractions occur as cervix approaches full dilatation?

A
  • 50 mmHg
  • Approaches 100-150 mmHg with maternal pushing effort
46
Q

Outline intrapartum monitoring

A
  • Intermittent monitoring with Doppler/pinard stethoscope
  • Every 15 minutes in 1st stage of labour and 5 minutes in 2nd stage
  • Continuous electronic foetal monitoring (CTG and foetal scalp electrode)
  • Foetal blood sampling to check pH
47
Q

How is labour induced?

A
  • Most commonly because mother is overdue
  • Membrane sweep at 39+ weeks
  • Prostaglandins (prostin vaginally)
  • IV oxytocin
  • Artificial rupture of membranes
  • Uses bishop’s score to see how favourable cervix is
48
Q

What are the indications for assisted delivery?

A
  • Failure to progress
  • Maternal exhaustion
  • Maternal conditions
  • Foetal compromise in 2nd stage
49
Q

What are the different types of assisted delivery?

A
  • Forceps
  • Suction cup/ventouse
50
Q

What are the indications for caesarean section?

A
  • Malpresentation
  • Macrosomia
  • Failure to progress
  • Foetal compromise
  • Foetal malformations
  • Previous caesarean