Fetal surveillance in labour Flashcards
(89 cards)
1
Q
What proportion of cerebral palsy is estimated to be due to intrapartum hypoxia?
A
10%
2
Q
What causes intrapartum hypoxia?
A
Blood supply to the placental pool is restricted, with contractions (especially in the second stage) placing a physiological strain on the fetus
Ability to withstand stress dependent on fetal reserve; may cope in antenatal period but have no extra reserve and decompensate in labour
3
Q
What are 2 options for intrapartum surveillance?
A
- Intermittent auscultation (IA)
- Continuous CTG, also known as electronic fetal monitoring (EFM)
4
Q
When should CTG be performed in the intrapartum period?
A
not advised routinely for low-risk women in suspected or established labour; should be performed is there is difficulty or some abnormality of the FHR on auscultation
5
Q
If CTG is performed due to FHR abnormality on auscultation, when can it be discontinued?
A
if CTG normal for 20 minutes
6
Q
What monitoring of the fetal heart rate should be performed in labour?
A
- on admission in labour, FHR should be auscultated for 1 min and entered as a single rate. Maternal heart rate should be palpated simultaneously to distinguish FHR as distinctly different
- if no risk factors, intermittent auscultation for full minute after a contraction
- at least every 15 min in first stage
- every 5 min or after every other contraction in the second stage
- any accelerations or decelerations that are auscultated should be recorded
- if fetal death suspected, US should be performed
7
Q
What are 9 antenatal maternal risk factors that should prompt recommendation of electronic fetal monitoring (continuous CTG) in labour?
A
- Previous caesarean section
- Cardiac problems
- Pre-eclampsia
- Prolonged pregnnacy (>42 weeks)
- Prelabour rupture of membranes (>24h)
- Induction of labour
- Diabetes
- Antepartum haemorrhage
- Other significant maternal medical conditions
8
Q
What are 7 fetal antenatal risk factors that should prompt recommendation of EFM (continuous CTG) in labour?
A
- IUGR
- Prematurity
- Oligohydramnios
- Abnormal doppler velocimetry
- Multiple pregnancy
- Meconium-stained liquor
- Breech presentation
9
Q
What are 7 intrapartum risks requiring EFM (continuous CTG)?
A
- Oxytocin augmentation
- Epidural analgesia
- Intrapartum vaginal bleeding
- Pyrexia >37.5oC
- Fresh meconium staining of liquor
- Abnormal FHR on intermittent auscultation
- Prolonged labour
10
Q
What are 2 disadvantages/effects of electronic fetal monitoring?
A
- increased intervention and operative delivery rates
- no marked decrease in cerebral palsy
11
Q
What are 5 reasons why EFM is likely to result in increased intervention and no marked decrease in cerebral palsy?
A
- CTG is not specific enough in detecting fetal hypoxia
- Failure to consider the clinical situation
- Poor interpretation
- Delay in taking action
- Intrapartum hypoxia as a cause of CP is rare
12
Q
What is are 2 that can be used alongisde EFM to increase specificity?
A
- fetal scalp blood sampling (FBS) - but recent studies questino its value
- ECG ST waveform analysis (STAN) - improves positive predictive value of CTG
13
Q
What is the definition of baseline rate when referring to cardiotocography?
A
mean level of the FHR when this is stable, and after exclusion of accelerations and decelerations
14
Q
What is the definition of baseline variability in reference to CTG?
A
degree to which the baseline varies, i.e. bandwidth of baseline after exclusion of accelerations and decelerations. Variability of 5–25 beats/min is defined as normal, 0–5 beats/min as reduced, and >25 beats/min as saltatory.
15
Q
What baseline variability of the CTG is considered 1. normal 2. reduced and 3. saltatory?
A
- Normal: 5-25 beats/min
- Reduced: 0-5
- Saltatory: >25
16
Q
What is the definition of acceleration in reference to CTG?
A
a transient rise in FHR from a steady baseline rate by at least 15 beats lasting for 15s or more
17
Q
What is the definition of deceleration in reference to CTG?
A
a reduction in the baseline of 15 beats or more for more than 15s.
18
Q
What does the CTG shown show?
A
several accelerations and normal baseline variability and no decelerations with contractions suggestive of healthy fetus
19
Q
What are the 2 most useful features in assessing fetal wellbeing from CTG?
A
- Normal variability: reflection of autonomic nervous system, sympathetic and parasympathetic
- Presence of accelerations: somatic nervous system
20
Q
When should you always be concerned about a CTG?
A
if you cannot identify the baseline rate
21
Q
What are 7 causes of decreased baseline variability in a CTG?
A
- Fetal hypoxia
- Fetal sleep cycle (should be for <40 and maximally 90min)
- Fetal malformation (CNS or cardiac) or arrhythmias
- Administration of drugs
- Severe prematurity
- Fetal heart block
- Fetal anomalies
22
Q
What are 7 examples of drugs which, when administered, can cause decreased baseline variability of the CTG?
A
- methyldopa
- magnesium sulphate
- narcotic analgesics
- corticosteroids
- transquilizers
- barbiturates
- general anaesthesia
23
Q
What are 2 examples of types of CTG abnormalities?
A
- Abnormalities in baseline rate
- Decelerations
24
Q
What is the definition of a bradycardia based on CTG?
A
baseline FHR of less than 110 beats/min
25
What are 2 groups that bradycardia based on the CTG can be classified into?
1. **100-110 beats/min:** moderate baseline bradycardia, on its own not associated with fetal compromise if baseline variability normal and accelerations present
2. **\<100 beats/min:** should raise possibility of hypoxia or other pathology
26
What should you be especially aware of if FHR is below 110?
maternal heart rate being recorded as the FHR
27
What is the definition of tachycardia based on CTG?
baseline FHR \>160 beats/min
28
What are 4 things which tachycardia in the fetus can be associated with?
1. Maternal pyrexia
2. Maternal tachycardia
3. Prematurity
4. Fetal acidosis
29
What are 2 groups that fetal tachycardia can be classed into?
1. **160-180 beats/min:** moderate baseline tachycardia, on its own likely not indicative of hypoxia if baseline variability normal and accelerations present
2. **\>180 beats/min** should always raise suspicion of underlying pathology
30
What are 2 types of decelerations on the CTG?
1. Early decelerations
2. Late decelerations
31
What is the definition of early decelerations?
the peak of the deceleration coincides with the peak of the contraction
this is related to head compression and therefore should only be seen in late first stage or active second stage of labour
32
What is the definition of late decelerations?
have at least a 20s time lag between the peak of the contraction and the nadir of the deceleration
33
What in particular may decelerations be suggestive of and what particularly supports this?
Acidosis; especially if accompanied by tachycardia and reduced baseline variability
34
What do shallow, late decelerations in the presence of reduced baseline variability on a non-reactive trace suggest?
should be of particular concern - may be **preterminal**, especially if associated clinical risks e.g. IUGR, absent FM, bleeding, infection, prolonged pregnancy, or severe pre-eclampsia
35
What are 6 things that, if associated with shallow, late decelerations, are suggestive of a preterminal fetus?
1. IUGR
2. Absent fetal movements
3. Bleeding
4. Infection
5. Prolonged pregnancy
6. Severe pre-eclampsia
36
What is meant by variable decelerations?
have variable pattern in timing, size, and shape and are associated with cord compression
37
What are typical deceleration variables on a CTG?
they are U or V shaped, quick to drop and to recover, and often have 'shouldering' - not usually associated with hypoxia
38
What are atypical deceleration variables on a CTG?
have a duration of \>60s, a loss \>60 beats from the baseline, slow recovery, combined variable and a late deceleration component
39
What is the effect of progressive hypoxia on decelerations on the CTG?
decelerations become deeper and wider with rising baseline rate
40
What does persistent reduction of baseline variability suggest on a CTG?
possible fetal acidosis
41
What are the 2 types of variable decelerations?
1. Typical variables
2. Atypical variables
42
What is the key thing which causes variable decelerations?
cord compression (therefore hypoxia)
43
What is a sinusoidal pattern on a CTG?
rare undulating pattern (sine wave) with little, or no, baseline variability
44
What are 2 things that a sinusoidal pattern on CTG can indicate?
1. Significant fetal anaemia
2. In short spells (\<10 min) can be behaviour (thumb sucking)
45
What 3 tests may be indicated if a sinusoidal pattern is found on CTG?
should always be taken seriously -
1. Blood group antibodies
2. Kleihauer test
3. Scan for middle cerebral artery velocity to detect fetal anaemia
46
What are the 3 types of variable decelerations that may be present in a CTG?
1. Typical variables
2. Atypical variables
47
What is the cause of early decelerations on a CTG and when is the only time you should see it?
this is related to head compression and therefore should only be seen in **late first stage or active second stage** of labour
48
What are the 3 groups that an CTG can be classified into when assessing the CTG as a whole?
1. Normal
2. Suspicious
3. Pathological
49
What baseline heart rate would you expect in a normal ('reassuring') CTG?
100-160
50
What variability would you expect in a normal ('reassuring') CTG?
≥ 5
51
What decelerations may be present in a normal ('reassuring') CTG?
None or early
52
What is an additional feature of a normal CTG that may not be present in suspicious or pathological CTGs?
accelerations
53
What is the expected baseline rate in a suspicious CTG?
161-180
54
What variability would you expect in a suspicious CTG?
\<5 for ≥30 but \<90min
55
What decelerations might you expect to see in a suspicious CTG?
* variable decelerations dropping from baseline by 60bpm or less and recovering in 60s or less present with \>50% of contractions over 90min
* Or variable decelerations \>60s or \>60 beats with \>50% contractions \>30mins
* Or late decelerations being present for \>50% of contractiosn for \>30min and not improving with resuscitative measures or bradycardia or single prolonged deceleration \>3min
56
What baseline beats/min would you expect on a pathological CTG?
\<100 or \>180
sinusoidal pattern for 10min or more
57
What variability would you expect on a pathological CTG?
\<5 for 90min or more
58
What decelerations may be present on a pathological CTG?
1. Non-reassuring variable decelerations as for suspicious CTG lasting \>30min after starting resuscitative measures
2. Or late decelerations being present for \>50% of contractions for ≥30min and not improving with resuscitative measures or bradycardia or single prolonged deceleration \>3min
59
What puts a CTG into the suspicious category and what should be done?
* one non-reassuring and two reassuring features - if accelerations present, acidosis unlikely
* conservative measures
60
What 2 further ways can pathological CTGs be classified?
1. Abnormal and needs conservative measures and further testing
2. Abnormal and indicates need for urgent intervention
61
What should prompt conservative measures and further testing following a pathological CTG?
one abnormal features or two reassuring features
combination of features that is more likely ot be associated with acidosis
62
What should prompt urgent intervention following a pathological CTG?
bradycardia or single prolonged deceleration with baseline \<100bpm \>3mins or an abnormal feature that is very likely to be associated with current fetal acidosis or imminent rapid development of acidosis
63
What are 7 maternal factors that may contribute to an abnormal CTG?
1. Woman's position: advise to adopt left lateral
2. Hypotension
3. Vaginal examination
4. Emptying blader or bowels
5. Vomiting
6. Vasovagal episodes
7. Siting and topping-up of regional anaesthesia
64
What is fetal blood sampling (FBS) used for?
to improve **specificity of CTG** in the detection of fetal hypoxia
should be obtained if trace is pathological, unless obvious immediate delivery may be required (e.g. bradycardia of \<80 beats/min for \>3min)
65
What position should a woman be in if fetal blood sampling is being performed?
left lateral
66
What is a normal result for CTG?
pH ≥ 7.25
67
What should you do if the fetal blood sample is normal but the CTG remains pathological?
repeat FBS within 1 hour
68
What is a borderline result for a fetal blood sample?
7.21 - 7.24
69
What should be done if the fetal blood sample is borderline but hte CTG remains pathological?
repeat FBS within 30min
70
What defines an abnoral fetal blood sampling result?
pH ≤ 7.20
71
What action should be taken if an abnormal CTG result is obtained?
immediate delivery
72
What have NICE said about the use of fetal blood sampling?
its validity has been question but they still recommend use of it
73
What 4 things make up meconiumk?
water, bile pigment, mucus, amniotic fluid debris
74
Why do we get concerned about detection of meconium in the amniotic fluid?
associated with increased perinetal morbidity and mortality - may be aspirated by fetus
75
How common is meconium-stained amniotic fluid (MSAF)?
rare in preterm infants (\<5%)
incidence increases from 36 to 42 weeks
76
What does the passage of meconium normally signify?
maturation of the central nervous system and gastrointestinal systems
77
What is a possible cause of meconium-stained amniotic fluid?
hypoxia causing peristalsis of the bowel and relaxation of the anal sphincters
78
How frequent is meconium aspiration syndrome?
occurs in 1:1000 births in Europe
79
What can cause meconium aspiration syndrome to occur in utero?
when fetal breathing movements draw amniotic fluid into the airway
80
What can cause fetal gasping in utero?
thought to be associated with prolonged decelerations that cause transient hypoxia, as 50% of meconium aspiration occurs in fetuses that were not acidotic in labour
81
What are 4 negative effects of meconium aspiration?
1. blockage of airway
2. acts as chemical irritant, causing pneumonitis and alveolar collapse
3. predisposes to secondary bacterial infection
82
What appearance of amniotic fluid is considered significant?
dark green or black meconium-stained fluid that is tenacious or contains lumps of meconium
83
What is the recommended management of meconium-stained liquor if prelabour rupture of membranes occurs?
* immediate induction of labour
* continuous fetal monitoring
* consider delivery if failure to progress needing oxytocin infusion, as hyperstimulation and prolonged deceleration may cause aspiration
84
What are 3 complications that meconium-stained amniotic fluid is associated with?
1. infection
2. chorioamnionitis
85
What is recommended if a newborn has respiratory difficulty/ depressed vital signs and liquor is meconium-stained?
* meconium should be cleared from oro- and nasopharynx and, if needed, from trachea by using **laryngoscopy and suction** (won't help with pre-existing in-utero aspiration)
* performed by health professional trained in advanced neonatal life support
86
What are 2 features that, if present, mean that infected meconium is likely to cause severe meconium aspiration syndrome?
1. maternal pyrexia
2. evidence of chorio-amnionitis
87
Where ideally should a baby be delivered if meconium-stained liquor has occured?
in a delivery unit able to provide fetal blood sampling and advanced neonatal life support at birth
88
What can be done if amniotic fluid is meconium-stained but the baby is born in good condition?
still needs close monitoring for **12** hours
89
