Oxford Handbook of Midwifery (59 page)

CHAPTER 11
Normal labour: first stage

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Cardiotocograph monitoring

Documentation

When continuous monitoring is commenced it is important to maintain a satisfactory tracing of fetal heart activity and contraction of frequency and strength. Maintain the CTG machine in good working order to ensure a satisfactory and accurate recording. Record the following information on the CTG paper:

• Date and time of commencing the CTG
  
• Name of the woman
  
• The woman’s hospital number
  
• The woman’s pulse rate—to establish that the tracing is the fetal heart rate
  
• Significant events, such as vaginal examination, siting of an epidural and epidural top-ups, augmentation with oxytocin, rupture of the membranes, and fetal blood sampling
  
• The CTG should be signed, dated, and the time noted
  

• When the birth is complete, the date, time, and mode of birth should be recorded, and the end of the trace marked clearly to verify that the whole of the trace has been retained.
  

  Fetal heart rate patterns
  

• Baseline rate
  : the normal baseline rate is between 110 and 160bpm. This is defined as the mean level of the fetal heart rate (FHR) when it is stable, which excludes periods of accelerations and decelerations.
  
• Baseline variability
  : is the variation in the baseline rate over 1min, excluding accelerations and decelerations. Normal baseline variability is greater than or equal to a minimum of 5bpm between contractions. Good variability is an important sign of fetal well-being.
  
• Reactivity
  : is the presence or absence of accelerations. In labour an acceleration is interpreted as a rise in the FHR of at least 15 beats for a minimum of 15s.
  
• Decelerations
  : a transient fall in the baseline rate of at least 15 beats for at least 15s. Decelerations are defined depending on their depth, shape duration, and time lag:
  
  • Early: these are usually a repetitive and consistent pattern. There is
    a slowing of the FHR with the onset of the contraction, returning to
    

    the baseline at the end of the contraction.
    

  • Variable: these are intermittent and variable in their timing, frequency and shape. The FHR slows down rapidly at the onset and are of short duration. May not occur with contraction cycle.
    
  • Late: a uniform and repetitive slowing of the FHR which commences at the mid to end of the contraction. The lowest point of the deceleration may be more than 20s past the peak of the contraction and finishing after the contraction.
    
  • Isolated prolonged: an abrupt decrease in FHR to levels below baseline that last at least 60–90s.
    

    The most common abnormalities of the FHR pattern during labour are decelerations, baseline tachycardia, and loss of baseline variability.
    

    CARDIOTOCOGRAPH MONITORING
    

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    Of these, the most worrying is loss of baseline variability together with shallow decelerations occurring after the peak of contractions.
    

A useful pneumonic to use for interpretation of the CTG trace is shown in Table 11.1.

Table 11.1
DR C BRAVADO to indicate:

CHAPTER 11
Normal labour: first stage

238‌‌

Monitoring fetal well-being

The fetal response to coping with the stress of labour can be assessed by the observational skills of the midwife and by clinical means, as follows:

• Fetal movements are always an indication of fetal well being, particularly during a contraction. Fetal activity may be felt abdominally or the woman questioned about the movements she is feeling.
  
• Auscultation of the fetal heart using a Pinard
  ^®
  fetal stethoscope, Sonicaid
  ^®
  , or electronic fetal monitor.
  
• Intrapartum events, such as augmentation with oxytocin, epidural anaesthesia, bleeding, etc. Electronic fetal monitoring needs to be commenced if the woman develops risk factors during labour.
  
• Condition of the amniotic fluid: meconium present in the amniotic fluid is of some value, but not always predictive of fetal distress. However, thick, fresh meconium may be indicative of fetal compromise and it is recommended that continuous electronic monitoring is commenced to establish any changes in the normal pattern of the fetal heart. Potential morbidity due to inhalation of meconium at birth must be prepared for. However, morbid inhalation of meconium is more likely to occur in utero when severe hypoxia causes agonal respirations prior to terminal apnoea.
  
• Because of the very close relationship between a mother and her fetus, a mother’s overanxiety regarding fetal well-being should be taken as a cue to start continuous monitoring.
  

  Electronic fetal monitoring
  

  Electronic fetal monitoring (EFM) was introduced initially to reduce peri- natal mortality and cerebral palsy. While a fall in the incidence of these conditions has not been demonstrated clinically, there has been a steep rise in interventions during labour. This has led to much debate about the value of continuous EFM in normal, low-risk labours.
  ¹
  

• The NICE guidelines
  ²
  recommend that in normal labour the admission trace should be abandoned and auscultation of the fetal heart should be carried out intermittently, with a Pinard
  ^®
  stethoscope or Sonicaid
  ^®
  , for up to 60s after a contraction, every 15min in the first stage of labour and every 5min in the second stage of labour unless the woman develops any risk factors. However the timings selected are not based
  

  on sound research evidence. Certainly during the early stages of
  

  normal labour, women are encouraged to remain at home and this amount of monitoring could be regarded as extremely intrusive.
  

• On admission, the maternal pulse should be recorded at the same time as the fetal heart, to differentiate between the two.
  
• EFM is poor at detecting normality, due to its high false-positive rate.
  ³
  
• Intrapartum hypoxia is a relatively rare occurrence. Therefore the risk of acidaemia is negligible if the pattern of the fetal heart rate falls into the reassuring classification.
  
• EFM affects the birth environment, changes relationships, and increases anxiety for the woman, birth supporters, and clinicians.
  ⁴
  
• With intermittent auscultation, the fetus is protected from recurrent, transient, and mild hypoxic episodes during labour. Therefore
  

  MONITORING FETAL WELL-BEING
  

  239
  

  individual variations in the fetal response to cope with labour is unmeasurable.
  ⁵
  Due to high levels of stress hormones the fetus is able to cope with prolonged periods of hypoxia and lowering of the heart rate during contractions.