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Scientific Basis of Midwifery > Physiology of 3rd Stage > Flashcards

Physiology of 3rd Stage Flashcards

1
Q

Define the 3rd stage of labour

A
  • Delivery to expulsion of placenta

- Most dangerous stage

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2
Q

How much has the placental site already diminished by at the start of the 3rd stage?

A

75%

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3
Q

Describe the process of the placenta detaching

A
  • Placenta becomes compressed
  • Blood in intervillous space forced back into spongy layer of decidua basalis
  • Retraction of oblique uterine muscles
  • With next contraction, distended veins burst and blood seeps between septa of spongy layer and placental surface, stripping it away
  • Retroplacental clot forms and shears off villi of spongy layer
  • Placenta detaches
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4
Q

What happens when the oblique muscles retract?

A
  • Pressure is exerted on blood vessels to prevent blood draining back into the maternal system
  • Blood vessels become tortuous as they are tense and congested with blood
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5
Q

What happens once separation has occurred?

A

Uterus contracts strongly, forcing the placenta and membranes to fall into lower uterine segment and then the vagina

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6
Q

Give some of the functions of the placenta

A
  • Respiration
  • Nutrition
  • Storage
  • Excretion
  • Protection
  • Endocrine
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7
Q

What are the 2 sides of the placenta?

A
  1. Amnion - foetal side, inverts during delivery (inside in utero, outside in air)
  2. Chorion - maternal side (bloody), inverts during delivery (outside in utero, inside in air)
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8
Q

Describe the umbilical cord

A
  • Outer layer = amnion
  • 2 arteries, 1 vein (AVA)
  • Surrounded by Wharton’s jelly
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9
Q

What forms in the placenta to aid separation?

A

Retroplacental clot

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10
Q

What does haemostasis mean?

A

Stopping the flow of blood

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11
Q

How long should the 3rd stage take?

A
  • Usually 5-30 mins but may take up to 1 hour
  • Active management = prolonged if not completed within 30 mins
  • Physiological management = prolonged if not completed within 60 mins
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12
Q

What is the normal blood flow through a healthy placental site?

A

500-800ml/min

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13
Q

What 3 factors control bleeding?

A
  1. Blood vessels
  2. Contractions
  3. Coagulation
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14
Q

Describe how blood vessels control bleeding

A
  • The tortuous blood vessels intertwine through the oblique uterine muscle fibres
  • Retraction of oblique muscles in upper segment results in thickening of muscles
  • This exerts pressure on torn vessels, acting as clamps and securing a ligature action
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15
Q

Describe how contractions control bleeding

A

Presence of vigorous contractions following separation bring the uterine walls into apposition so that further pressure is exerted on the placental site

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16
Q

Describe how coagulation controls bleeding

A
  • Haemostasis is achieved by a transitory activation of coagulation and fibrinolytic systems during and immediately following placental separation
  • This is especially active in placental site so clot formation in torn vessels is intensified
  • Following separation, placental site is rapidly covered by fibrin mesh, utilising 5-10% of circulating fibrinogen
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17
Q

Give 6 signs of placental separation

A
  1. Contracted uterus
  2. No excessive bleeding but a small, fresh blood loss
  3. Lengthening of cord
  4. Fundus becomes smaller, rounder and more mobile
  5. Fundus rises above placental level
  6. Placenta is visible at the vagina
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18
Q

What are the 2 types of placental separation?

A
  1. Shultze

2. Matthew Duncan

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19
Q

Describe the Shultze separation

A
  • ‘Shiny side up’
  • Separation begins centrally
  • Forms a retroplacental clot
  • Foetal surface appears first
  • Shorter duration than Duncan
  • Less blood loss
  • Complete membranes and retroplacental clot visible on examination
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20
Q

Describe the Matthew Duncan separation

A
  • Separation begins at lateral border
  • No retroplacental clot
  • Maternal surface appears first
  • Longer duration than Shultze
  • More blood loss
  • Ragged membranes visible on examination
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21
Q

What was a major cause of maternal death in the first half of the 1900s?

A
  • PPH (8-22%)

- Decreased to 4-8% by 1978 due to increase availability of blood transfusions, improved nutrition and antenatal care

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22
Q

When was the first routine use of ergometrine?

A

0.5mg in 1951

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23
Q

What became the drug of choice in the 1960s?

A

Syntometrine

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24
Q

Describe physiological management of the 3rd stage

A
  • Minimal intervention, no drugs
  • No cord clamping until after placenta delivery/ cord pulsation has ceased
  • Placenta and membranes delivered by maternal effort, guided by gravity
  • Encouragement very important
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25
Q

Why would an oxytocic agent be administered in physiological management?

A
  • Uterine tone is poor
  • Mother’s condition deteriorates
  • Mother requests it
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26
Q

What helps with physiological management?

A

BF as it results in reflux release of oxytocin which encourages the uterus to contract

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27
Q

Describe active management

A
  • Routine administration of uterotonic drugs
  • Cord clamping shortly after placenta delivery
  • Use of CCT
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28
Q

What is CCT?

A

Controlled Cord Traction

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29
Q

Describe CCT

A
  • Gently pull on umbilical cord and push uterus with each contraction until placenta is delivered (counter traction)
  • Designed to enhance normal physiological process
  • Incorporated in active management
  • Reduces time in 3rd stage to reduce blood loss
30
Q

What is a cord prolapse?

A

Umbilical cord comes out with/ before the presenting part (before baby is delivered)

31
Q

What should be checked prior to CCT?

A
  • Has oxytocic drug been given?
  • Has time been allowed for it to act?
  • Is uterus well contracted?
  • Are there signs of placental separation and descent?
32
Q

What should not be done during CCT?

A
  • Do not apply traction to cord if placenta is not separated - risk of uterine inversion
  • No ‘fundal fiddling’ (repeatedly palpating uterus) as this will cause the uterus to relax
33
Q

What are the 3 main drugs used?

A
  1. Syntocinon
  2. Ergometrine
  3. Syntometrine
34
Q

Describe syntocinon

A
  • Synthesised oxytocin
  • Prevents and treats haemorrhage during 3rd stage
  • Also used for induction and augmentation
  • Must not be used for women with raised BP
35
Q

What is the normal dosage for syntocinon?

A
  • 40 units in 500ml of N/Saline via Hartmann’s IV
    OR
  • 5 units of oxytocin (slow bolus IV) - administered slowly due to profound and potentially fatal hypotensive side effects
36
Q

Describe ergometrine

A
  • Oxytocic drug given at end of labour
  • Controls bleeding
  • Causes strong, sustained contractions
  • Acts within 6-7 mins (IM)
  • Contra-indicated if there is a history of hypertensive or cardiac disease
  • Used IV if haemorrhage due to hypotonic uterine action as it secures rapid contraction in 45 seconds
37
Q

What is the normal dosage of ergometrine?

A

500mg in 1ml (IM) with oxytocin 5 units

38
Q

Describe syntometrine

A
  • Syntocinon and ergometrine mixed
  • Oxytocin stimulates contractions and ergometrine sustains them
  • Effects last for several hours
  • Effective in 2-3 mins when given IM
  • Side effects = raised BP and vomiting
39
Q

What is the normal dosage for syntometrine?

A 
Oxytocin = 5 IU in a 1ml ampoule
Ergometrine = 0.5mg in a 1ml ampoule
40
Q

When does administration of a uterotonic drug usually take place?

A

As the anterior shoulder of the baby is born

41
Q

What should be done on completion of the 3rd stage

A
  • Estimation of blood loos
  • Examination of placenta
  • Examination of perineum
42
Q

What are the common volumes of blood lost?

A
  • Normal delivery = up to 250ml is acceptable
  • Woman sitting in pool of blood = 250-300ml
  • Blood spilling off bed = 500ml (risk of haemorrhage)
43
Q

What observations should be done following 3rd stage?

A
  • If there is excessive bleeding but uterus has contracted well, it may be coming from somewhere else (e.g. perineal/ cervical tear)
  • Never leave mother and baby on their own for first few hours (e.g. risk of mother fainting)
  • After placenta is delivered and everything is cleared up, check perineum again for blood loss before leaving
44
Q

What should be checked on the placenta?

A
  • Hold up by cord to check membranes for completeness
  • Check number of vessels
  • Check for succenturiate lobe
  • Strip back amnion from chorion to cord to ensure both are present
  • Examine chorion
  • Estimate blood loss
  • Record findings
45
Q

What may the absence of an artery in the umbilical cord be associated with?

A

Renal disease in the baby

46
Q

What is a succenturiate lobe?

A
  • Check for vessels around edge of placenta

- Small extra lobe in addition to main placenta and attached via blood vessels

47
Q

What should be checked on the chorion?

A
  • Check all lobes are present
    Check for:
  • Infarcts (dead cells - fatty deposits cause placenta to break away from uterus lining)
  • Calcification (hardened areas caused by accumulation of calcium salts)
  • Missing pieces
48
Q

What should be done if part of the placenta/ membranes are missing?

A
  • Woman is given antibiotics

- Blood clots should be monitored by midwife until all has come out

49
Q

What is a bipartite placenta?

A
  • 2 complete and separate parts with a cord leaving each part which join a short distance from the placenta
  • Placenta in twins are separate with 2 separate cords
50
Q

What is a battledore insertion?

A

Cord is attached at the very edge of the placenta

51
Q

What is a velamentous insertion?

A

Cord is inserted away from the edge of the placenta in the membranes

52
Q

What are the 3 main complications that may occur in 3rd stage?

A
  1. PPH - excessive bleeding from genital tract at any time after baby’s birth up to 24 hours
  2. Blood Loss - reaching 500ml must be treated as a PPH
  3. Secondary PPH - abnormal or excessive bleeding from genital tract occurring between 24 hours and 12 weeks postnatally
53
Q

Give 8 reasons that a PPH might occur?

A
  1. Atonic uterus
  2. Retained placenta
  3. Trauma
  4. Blood coagulation disorder
  5. Previous history of PPH/ retained placenta
  6. High parity
  7. Anaemia
  8. HIV/AIDS
54
Q

What is an atonic uterus?

A

Failure of the myometrium at the placental site to contract and retract and to compress torn blood vessels to control blood loss by living ligature action

55
Q

What are the 3 principles of care in PPH?

A
  1. Call for help
  2. Stop the bleeding
  3. Resuscitate the mother
56
Q

If the uterus is firmly contracted, how should bleeding be stopped?

A
  • Lower genital injury = apply pressure and repair the wound
  • Ruptured uterus = laparotomy (repair the tear) or hysterectomy
  • Clotting disorder?
57
Q

If uterus is atonic, how should bleeding be stopped?

A
  • Rub up a contraction
  • Give oxytocin - put baby to breast, give ergometrine (0.5mg IV) or syntocinon (4.0 u/L IV)
  • Empty bladder (bedpan/ catheter)
  • Empty the uterus
58
Q

How should the uterus be emptied if the placenta has been delivered?

A

Expel clots; if this fails to arrest bleeding, apply bimanual compression and perform hysterectomy

59
Q

How should the uterus be emptied if the placenta is undelivered but separated?

A
  • Grasp and remove if in vagina
  • Use CCT if in lower uterine segment
  • If this fails to arrest bleeding, apply bimanual compression and perform hysterectomy
60
Q

How should the uterus be emptied if the placenta is undelivered and unseparated (retained)?

A
  • Attempt manual removal
  • Unsuccessful = placenta accreta
  • Give antibiotics or perform hysterectomy
61
Q

What is placenta accreta?

A

Blood vessels and other parts of the placenta grow too deeply into uterine wall to be removed

62
Q

How should the mother be resuscitated?

A
  • Restore circulation
  • Assess postnatal Hb levels
  • Correct as appropriate
63
Q

How is bimanual compression applied?

A
  • Apply pressure to placental site
  • Insert fingers of one hand into vagina like a cone
  • Form hand into fist and place into anterior vaginal fornix
  • Place other hand behind uterus abdominally, fingers pointed towards cervix
  • Bring uterus forward and compress between palm of abdominal hand and fist in vagina
64
Q

What are the pregnancy related causes of an atonic uterus?

A
  • Multiple pregnancies

- Polyhydramnios - causes overdistension of the uterine muscle

65
Q

What placental conditions may cause an atonic uterus?

A
  • Placenta praevia as it partly/wholly lies in lower segment where thinner muscle layer contains few oblique fibres, resulting in poor control of bleeding
  • Placental abruption as blood may have seeped between muscle fibres, interfering with effective muscle action - severe cases result in a Couvelaire uterus
66
Q

What sort of labour may cause an atonic uterus?

A

Precipitate labour (very fast) and prolonged labour resulting in uterine inertia (absence of effective contractions) resulting from maternal exhaustion/ sluggishness

67
Q

What other factors may cause an atonic uterus?

A
  • Incomplete retained placental fragments/ membranes and cotyledon
  • Full bladder interferes with uterine action
  • General anaesthesia may cause uterine relaxation
68
Q

What are cotyledon?

A

Separations of the placenta

69
Q

When would a uterus be described as ‘boggy’?

A

On palpation, an enlarged uterus filling with blood/ clots feels soft and distended and lacking tone

70
Q

When would cord blood sampling usually be taken?

A

When atypical maternal antibodies have been found during antenatal screening tests

Scientific Basis of Midwifery (22 decks)

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