Electronic fetal monitoring

Electronic fetal monitoring with the cardiotocograph is standard practice during labour in most obstetric units in the United Kingdom. The technique was introduced as a screening test in the 1970s in the belief that it would improve the detection of fetal hypoxaemia and reduce cerebral palsy and perinatal mortality, particularly in high risk pregnancies. Early retrospective observational studies supported the view that it was superior to intermittent auscultation using either a Pinard stethoscope or a hand held doppler ultrasound device.¹ Its use spread rapidly from high risk to low risk pregnancies where the fetus is at least risk from hypoxic events in labour. Was this spread necessary or wise?

By the 1990s systematic reviews of randomised controlled trials of electronic fetal monitoring versus intermittent auscultation during labour had shown no effect on neonatal outcomes such as metabolic acidosis at birth, low Apgar scores or admissions to neonatal intensive care.^2–4 An increase in neonatal seizures was seen in the group with intermittent auscultation but no long term increase in neurological problems.⁵

Electronic fetal monitoring did, however, have an effect on women in labour. Levels of obstetric intervention—augmentation of labour, epidural anaesthesia, instrumental delivery, and caesarean section—consistently increased.⁴ Instrumental delivery and caesarean section were even more common when electronic fetal monitoring was not backed up by fetal blood sampling. The impact on the mother and her experience of labour was therefore considerable, without any gain for the baby. In many units this evidence allowed a return to intermittent auscultation, which is less intrusive for the woman. Unfortunately the dramatic increase in litigation in obstetrics has tempered this change, as the cardiotocograph has also become an important legal document.

An admission cardiotocograph was introduced to identify fetuses at risk which needed closer monitoring during labour, allowing those with no signs of distress to be monitored by intermittent auscultation.⁶ In their large randomised controlled trial in this week's BMJ Mires et al show that even this brief cardiotocograph on admission has a similar effect in low risk women to the use of the cardiotocograph throughout labour (p 1457).⁷ The intervention rate increased significantly with no effect on neonatal outcome.

In low risk pregnancies adverse events during labour that affect the development of the baby are rare. Most cases of cerebral palsy have antecedents in the antenatal period,⁸with only about 10% of cases having an intrapartum cause. The prevalence of perinatal mortality or cerebral palsy from intrapartum causes is about 0.8 per 1000 and 0.1 per 1000 respectively.¹ Most studies of electronic fetal monitoring were underpowered to detect these rare events and have concentrated on more immediate fetal outcomes. When perinatal mortality was studied no effect was seen. Nevertheless, the cardiotocograph continues to be an important document in many legal cases concerning cerebral palsy.

So the evidence is strongly against the routine use of electronic fetal monitoring. This is further reinforced by the publication last month of the Royal College of Obstetricians and Gynaecologists' guidelines on electronic fetal monitoring, which have been developed with the National Institute for Clinical Excellence.¹ This important document has brought together all the good evidence on electronic fetal monitoring. There are some important messages, which should affect practice on labour wards throughout Britain.

The chief recommendation is that intermittent auscultation is the most appropriate method of fetal monitoring for women in labour who are low risk. This allows the best compromise between assuring fetal safety and allowing the woman mobility and independence during labour. For auscultation to be successful it needs to be frequent, especially in the second stage of labour, and therefore requires one to one care of the woman. Unfortunately this is an ideal which may be impossible in hard pressed labour wards, where midwives are often in short supply. Ironically, there is good evidence that one to one care alone has a powerful effect on the labouring woman, reducing intervention.⁸ The cardiotocograph can become a surrogate for this best quality care and has a major impact on the caesarean section rate.

If intermittent auscultation identifies a problem or the woman has major risk factors then electronic fetal monitoring should be used. The main problem then lies in interpreting the cardiotocograph trace. The guidelines address this at length and provide good criteria for identifying suspicious and abnormal traces. Another key recommendation is that all professionals involved in managing labour should have regular, continuing training in interpreting and storing cardiotocographs. This recommendation is in line with three recent Confidential Enquiries into Stillbirths and Deaths in Infancy, which have consistently recognised inadequate interpretation of the cardiotocograph as a prime cause of adverse events.^9–11To prevent litigation trusts should act on this recommendation and ensure that such training is available free for all relevant staff.

The guidelines have also looked at other methods of testing fetal well being in early labour and of fetal monitoring, such as fetal pulse oximetry and fetal electrocardiography. These newer tools may be useful as an adjunct to electronic monitoring, but they are no more predictive of adverse outcomes. Research is needed to identify more specific tests of fetal well being that will allow us to identify babies at risk during labour without having a major impact on women. For now, it is important that electronic fetal monitoring should be used appropriately in high risk women and that intermittent auscultation is recognised as a valid form of management for most low risk cases.

Papers p 1457