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Labour Flashcards

1
Q

Parturition

A

Process of labour
begins much prior to actual onset of regular uterine contractions
uterus comproised predominantly of smooth muscle fibers

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2
Q

Phase 0 of labour

A

uterine quiescence

contractile tranquility

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3
Q

Phase I of labour

A

uterine preparedness

functional changes in myometrium + cervix

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4
Q

Phase II of labour

A

active labour

progressive cervical dilation and fetal delivery

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5
Q

Phase III of labour

A

uterine involution

fertility restored

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6
Q

Elements of Parturition

A

requires agents that stimulate onset of uterine regular contractions along with cervical effacement + dilatation

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7
Q

Uterotropins

A 
agents that set the stage for regular uterine contractions and cervical change
estrogen
relaxin
Ca-dependent phospholipases
arachidonic acid (prostaglandin)

Progesterone counteracts actions of these uterotropins: maintains uterine quiescence

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8
Q

Uterotonins

A

agents directly involved in causing myometrial smooth muscle cells to contract
increased intracellular calcium in myometrium

oxytocin
prostaglandins (specifically PGF2alpha)
endothelin-1

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9
Q

Sheep model of labour

A

1) increased ACTH from fetal pituitary
2) increased cortisol from fetal adrenals
3) increased androgens from placenta (estrogen precursors)
4) increased estradiol in mother
5) decreased progesterone in mother

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10
Q

Parturition initiation in humans

A

however in humans, prior to onset of active labour (as opposed to sheep):

  • serum progesterone levels do NOT fail
  • serum estradiol levels do NOT rise
  • administration of progesterone does NOT reliably prevent preterm labour
  • administration of estrogen does NOT induce labour
  • prostaglandins, arachidonic acid, relaxin, phospholipases, cortisol, oxytocin do NOT rise until active labour
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11
Q

Phase II of labour - prostaglandins

A

synthesized at/near site of action (interface of amnion/chorion and myometrium)

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12
Q

PGE2 i nlabour

A

cervical effacement
highest levels in amniotic fluid just below presenting part “forewaters”
breakdown of rigid structure of collagen fibers
unwinds collagen fibers
softens extracellular matrix
increased hyaluronic acid
decreased glycosaminoglycans

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13
Q

PGF2alpha in labour

A

Thinning of lower uterine segment during active labour –> inflammatory response in decidua –> arachidonic acid released
Process also stimulated by oxytocin

Leads to increase in intracellular calcium

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14
Q

Relaxin

A

peptide hormone originating from ovary
also involved in cervical ripening
unknown how it interacts with PGE2

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15
Q

Oxytocin

A

precursor produced in hypothalamus
secreted from post. pit in active labour
increase intracellular Ca (via activation of phospholipase C)
Oxytocin receptors present on myometrium:
- increase near term
- increased by estradiol: estrogen involved in labour induction
- down-regulated by progesterone through rest of pregnancy

Oxytocin used in late pregnancy (IV) for inducing labour
- not effective earlier on because fewer receptors

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16
Q

Myometrial contractions

A

muscle filaments: thick/thin filaments arranged in long random bundles to allow muscle shortening in any direction and maximize shortening

Gap junctions:

  • transcellular membrane channels
  • allow ion exchange between cells
  • propagate electrical signal
  • increase muscle shortening
  • increase in number close to parturition
  • increased by estradiol
  • decreased by progesterone
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17
Q

Myometrial relaxation

A

decreased intracellular Ca
sequestration of Ca into SR
Dephosphorylation of myosin light chain
inactivation of myosin light chain kinase (by cAMP-dependent phosphorylation)
labour continuous process of alternating contractions/relaxations

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18
Q

Phase II clinical features

A 
Lower uterine segment (passive segment + cervix) thinning and dilating
upper uterus (active segment) thickens with continuing uterine contractions
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19
Q

Summary of labour physiology

A

1) Cervical ripening
- stimulated by estradiol, arachidonic acid, PGE2
- inhibited by progesterone
2) contractions
- increased intracellular Ca due to PGF2alpha, oxytocin/oxytocin receptors
- increased # of gap junctions due to estradiol, inhibited by progesterone

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20
Q

Induction of labour

A

amniotomy
membrane sweeping (inflammatory action)
Foley catheter in cervix (increase mechanical pressure for prostaglandins)
oxytocin

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21
Q

Preventing preterm labour

A

NSAIDs
progesterone
Ca channel blockers

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22
Q

Evaluation of labour

A 
Hx
Physical: vital signs
general exam
fetal heart rate
abdominal exam
SFH
Leopold maneuvers
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23
Q

Leopold maneuvers

A

1) palpate uterine fundus for contents
2) palpate fetal back on one side and limbs on other
3) palpate fetal presenting part just above symphysis
4) facing patients feet, determine fetal position (also confirmed on internal exam with a dilated cervix)

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24
Q

Occiput:

A

head flexed lowest part

anterior - facing maternal symphysis
45 degrees to symphysis on maternal left side - left occiput anterior
maternal sacrum - occiput posterior/OP

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25
Lie of fetus
description of long axis of fetus relative to long axis of mother longitudinal, oblique or transverse
26
Presentation of fetus
cephalic, breech or shoulder
27
Presenting part of fetus
``` part closest to cervix occiput face brow sacrum lower limbs ```
28
Position of fetus
Orientation to maternal pelvis | e.g. left occipus anterior
29
Station of fetus
measure of degree of descent of presenting part (relation to maternal ischial spines)
30
Definition of labour
progressive cervical dilation, effacement, or both, resulting from regular uterine contractions every 5 minutes lasting 30-60 sec
31
1st stage of labour
onset of involuntary painful regular contractions to full dilation (10 cm) latent/active phases
32
Latent phase - labour
onset of regular painful contractions q5 min lasting 30-60 sec cervix
33
Active phase - labour
regular painful contractions q2-3 min lasting 45- 60 sec cervix 3-4 cm to fully dilated (10 cm) nulliparas: 1cm /hr multiparas: 1.2 cm/hr
34
Second stage of labour
``` full dilation to delivery of fetus maternal pushing increases forces directing fetus downwards and outwards - push against a closed glottis - increase intra-abdominal pressure - descent of fetus into pelvis ``` Majority of pushing effort actually from uterine contractions, assisted by maternal pushing efforts Nulliparas: 50 min - 3 h multiparas: 20 min
35
Cardinal movements of delivery
minimize fetal diameter as they pass through narrowest diameters of pelvis 1) Engagement 2) Descent 3) Flexion 4) internal rotation 5) extension 6) external rotation/restitution 7) expulsion
36
third stage of labour
delivery of fetus to delivery of placenta 0-30 min (>90% deliver by 15 minutes) blood clot forms at plane of cleavage placenta slides into lower uterine segment delivery occurs by maternal pushing and gentle traction on cord management
37
Classic signs of placental separation
Gush of blood lengthening of cord fundus rises up uterus becomes firm and globular
38
Active management of 3rd stage of labour
proven to reduce incidence of postpartum hemorrhage uterotonics with delivery (oxytocin, misoprostol) gentle, controlled cord traction controversion - early cord clamping?
39
Pain in labour - early
Sensory impulses from lower uterine segment/cervix travel via visceral afferent nerve fibers to spinal cord, entering at T10-L1 nerve roots - major pain pathway of first stage
40
Pain in labour - later first stage/2nd stage
once fetal presenting part has reached pelvic floor and during second stage, pain from pelvic structures and vagina travel via somatic afferent nerve pathways to L1-S4 Pain from perineum conducted through pain fibers of pudendal nerve - S2-S4 Pain relief in labour is affected by selective anesthesia of nerves involved
41
4th stage of labour
``` delivery of placenta to stabilization of maternal condition 1-1.5 h after delivery of placenta bleeding slows uterus remains contracted maternal stabilization/bonding first attempt at breastfeeding ```
42
Phase III of pregnancy
6 weeks following delivery Most physiological changes return to non-pregnant state uterine bleeding stops by contraction of muscle around vessels and thrombus formation - decidua basalis remains with myometrium and becomes regenerated endometrial lining - no scar forms superficial layer gets sloughed as lochia rubra, lochia serosa, lochia alba
43
Involution of uterus
gradual decrease in size of body of uterus (decrease in myometrial cell size, not #) IMmediately after delivery of placenta, fundus palpable just below umbilicus: ~1 kg Intermittent oxytocin release --> continues contractions (afterpains) - in response, uterus gradually decreases in size 3 weeks after delivery: uterus no longer palpable above symphysis; weighs ~300 g 4 weeks after delivery: returned to nonpregnant size, sloughed after 3 weeks As endometrium regenerates, vascular bed covered over --> no scarring
44
Cervix post-delivery
cervix lengthens - external os remains funneled (multiparous os)
45
Lochia
normal vaginal discharge postpartum
46
Lochia rubra
originally red due to RBCs | 4 days
47
Lochia serosa
after 4 days increasing leukocytes - pale
48
Lochia alba
after 10 days - normally yellow/white
49
Ejection of milk
suckling stimulates oxytocin myoepithelial cells around alveoli in breast glands contract milk ejected
50
Lactation
delivery of placenta - -> decreased estrogen/progesterone - -> increased PRL - -> milk production
51
Other physiological changes with peurperium
muscles of abdominal walls remain lax - rectus muscles can separate: diastasis - striae Diuresis of increased circulatory volume - eliminate increased blood volume in 1st week - associated with increase in CO in first 48 hours Reduction in size of pelvic blood vessels reduction in coagulation factors: gradually fall over 6 weeks Menses resume/fertility restored
52
Weight loss post-partum
Weight loss of ~15 kg; - 7kg for baby, placenta, blood loss (immediate) - 3kg for diuresis (over 2-5 days) - 5kg for involution of uterus and decreased blood volume (over 5 weeks)
53
Resumption of menses
Absence of breastfeeding --> reduction in PRL level --> serum estrogen restored, ovulation resumes may occur in 6-8 weeks postpartum Phase III complete with resumption of menses
54
Postpartum hemorrhage definition
excessive bleeding in first 24 hours after delivery vaginal delivery: >500 ml of estimated blood loss C-section: >1000 ml clinical definition = blood loss that can produce hemodynamic instability
55
Causes of postpartum hemorrhage
Tone Tissue Trauma Thrombin
56
Tone in postpartum hemorrhage
atony --> most common cause of PPH (80%)
57
Risk factors of atony in PPH
failure to actively manage 3rd stage uterine distention (due to polyhydramnios, twins, macrosomia) uterine exhaustion --> precipitous labour, prolonged labour, high parity infection --> prolonged rupture of membranes function/anatomical distortion of uterus --> fibroid, previa prior to PPH Bladder distention preventing uterine contraction
58
Tissue risk factors in PPH
Retained placenta Succenturiate lobe clots abnormal placentation leading to retained placenta, membranes, clot
59
Trauma risk factors in PPH
precipitous/operative vaginal delivery leading to vaginal, cervical or uterine injury
60
Thrombin risk factors for PPH
pre-existing/acquired risk factors (history of easy bruising, prior PPH, massive blood loss --> DIC)

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