It is important to remember the following learning points regarding EFM:
- it is used to identify intrapartum hypoxia – a significant cause of fetal death and disability; fetal hypoxia can lead on to fetal asphyxia and death
- it should not be used unless indicated as it increases the rates of caesarean section and instrumental delivery in low-risk women
- it has become an integral component of labour management in high-risk women.
Fetal hypoxia is a major cause for perinatal death, neonatal morbidity and neurodevelopmental disability. Hypoxic brain injury or death of the fetus accounts for nearly 38% of claims handled by the Medical Defense Union and Medical Protection Society in the UK. The effect of hypoxia on the fetal brain is reflected on the changes in fetal heart rate patterns.
- Limitations imposed by the use of continuous EFM:
- reduced mobility
- possibility that woman will not be the centre of care in labour
- increased intervention
- variation in interpretation of CTG trace
- chorioamnionitis could make interpretation unreliable
- litigation; therefore, good record-keeping is crucial.
- From 26 weeks onwards, decelerations of the fetal heart should be regarded as abnormal.
- Intrauterine infection leads to a rise in perinatal morbidity and mortality and, in this context, the CTG is less sensitive at detecting hypoxia.
- No CTG should be interpreted without a full understanding of the clinical picture.
- When hypoxia develops gradually, the first features to be noted are the absence of accelerations, increase in baseline rate and reduction in baseline variability. The worsening situation may be reflected by the deceleration getting deeper and wider.
- In a non-reactive trace, when the baseline variability is less than 5 beats/minute, shallow decelerations of less than 15 beats may indicate an ominous pattern.
- Head compression and true cord compressions are associated with activation of the parasympathetic nervous system and, hence, result in early and variable decelerations, respectively, both of which are short-lasting.