CASE 79: LABOUR
History
A midwife is concerned about a cardiotocograph (CTG) on the labour ward. The woman
is 42 years old and had an elective caesarean section 3 years ago for twins. After counselling, she decided to opt for a vaginal delivery in this pregnancy. She is now at a gestational age of 38 weeks and 1 day and presented to the labour ward an hour ago. She
was found to have contractions, three in 10 min lasting 50 s each. There was no reported
rupture of membranes.
At the time of arrival, examination revealed a symphysiofundal height of 39 cm, cephalic presentation and 3/5 palpable abdominally. Vaginal examination revealed intact membranes with
the head 1 cm above the ischial spines, occipitoanterior position and the cervix 5 cm dilated.
She was commenced on continuous CTG monitoring (because of the previous caesarean
section), which showed an initial baseline rate of 135/min, good variability, accelerations and
no decelerations.
Twenty minutes ago spontaneous rupture of membranes occurred with clear liquor leaking.
INVESTIGATIONS
The CTG is shown in Fig. 79.1.
Questions
• Describe and classify the CTG.
• What are the possible causes for this CTG pattern?
• What should be your subsequent management?
100
200
02:10 02:20 02:30
180
160
140
120
100
100
75
50
25
UA
100
75
50
25
UA
80
60
HR
200
180
160
120
100
80
60
HR
200
180
160
140
120
100
80
60
HR
75
50
25
UA
140
Figure 79.1 Cardiotocograph.100 Cases in Obstetrics and Gynaecology
220
ANSWER 79
The CTG shows a baseline rate of 130/min and variability of 15/min. There are atypical variable decelerations to approximately 70/min lasting 30–90 s. Although there are no normal
accelerations there is ‘shouldering’ before and after the decelerations, a sign of the fetus
increasing its heart rate in response to the increased blood flow after the deceleration. The
fetal heartbeat is only just recovering to the baseline between decelerations.
This CTG is unsatisfactory because the tocometer is not registering contractions.
Management
In this situation, the recent history of spontaneous rupture of membranes indicates immediate vaginal assessment to rule out cord prolapse as the cause of the suddenly abnormal
CTG. This would be a classic presentation for cord prolapse, though the condition itself is
very rare.
Much more commonly variable decelerations are caused by cord compression (by the uterine
wall or, for example, by the fetal hand).
If, as is normally the case, the cord is not palpable and the baby is not easily deliverable by
instrumental delivery, then further assessment of fetal wellbeing is required as the abnormality of the CTG has already lasted some time. This should be by fetal blood sampling (FBS).
In this case FBS gave the following result:
pH: 7.23
Base excess: –4.0 mmol/L
With a pH between 7.20 and 7.25, it is reasonable to manage the woman expectantly and
repeat the FBS in 30 min. This was done and the second result was:
pH: 7.22
Base excess: –5.1 mmol/L
At this stage the woman was fully dilated and pushing involuntarily, and the baby was delivered spontaneously soon after the sample was taken.
In this case the fetal blood pH was relatively reassuring despite the dramatic appearance of
the CTG. It is possible to avoid caesarean section in such cases with appropriate use of FBS.
It should be remembered that FBS is contraindicated in certain conditions such as maternal
HIV, hepatitis or potential fetal-bleeding disorders.
KEY POINTS
• CTGs are classified according to national guidelines (as shown in Tables 79.1 and
79.2).
• FBS can often confirm fetal wellbeing despite a non-reassuring or abnormal CTG,
and thus avoid an unnecessary operative delivery.Case 79: Labour
221
Table 79.1 Definition of normal, suspicious and
pathological FHR traces
Category Definition
Normal All four features are classified as reassuring
Suspicious One feature classified as non-reassuring and
the remaining features classified as
reassuring
Pathological Two or more features classified as nonreassuring or one or more classified as
abnormal
Table 79.2 Classification of FHR trace features
Feature Baseline
(beats/min)
Variability
(beats/min)
Decelerations Accelerations
Reassuring 110–160 ≥5 None Present
Nonreassuring
100–109
161–180
<5 for
40−90 min
Typical variable
decelerations with
over 50% of
contractions, for over
90 min
Single prolonged
deceleration for up to
3 min
The absence of
accelerations with
otherwise normal trace
is of uncertain
significance
Abnormal <100
>180
Sinusoidal
pattern
≥10min
<5 for 90
min
Either atypical variable
decelerations with
over 50% of
contractions or late
decelerations, both for
over 30 min
Single prolonged
deceleration for more
than 3 min
Source: NICE Clinical guideline 55: Intrapartum Care (September 2007)
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