Cardiotocography v Doppler auscultation

Author of editorial�s reply to electronic responses

It is not surprising that the publication of the paper by Mires et al and my accompanying editorialresulted in a wide range of responses from both sides of the argument.⁽¹⁾ ⁽²⁾This issue has long been controversial and, as indicated in the letters by Smith and Grant, is likely to remain so as it may prove impossible to carry out a large enough trial with sufficient power to answer the key question: Can electronic fetal monitoring either on admission or during labour reduce the risk of poor obstetric outcome by identifying those infants who are stressed by labour where early intervention will improve the outcome?

Unfortunately, cardiotocography is a poor screening test, especially in low risk women, which has been widely introduced into practice without the evidence for its value. As Bernardes and Costa-Pereira state there are wide variations in interpretation of traces. It is also a test, which is highly sensitive for a rare disease but has a low specificity.⁽³⁾ As a consequence, the false positive rate is high leading to a high intervention rate. While many obstetricians such as Smith, Grant, and Clow feel that any increase in caesarean rate is justified if there is perceived to be a neonatal benefit, many others disagree particularly where epidemiological data would suggest that there has been no effect on mortality. In particular midwives (Hulme Hunter), pregnant women themselves, and other professionals who may have to deal with the long-term effects of our management (Dolan), are dismayed at the escalating intervention rate that has occurred as a consequence of using electronic monitoring in low risk women.

It is unfortunate that the method used in this trial was different to that used in other randomised controlled trials comparing the two techniques (Grant). The paper by Mires et al was in proof before the new guidelines from the Royal College of Obstetricians and Gynaecologists (RCOG) were published. I agree with Stuart�s point that there is no grade A evidence for the form of intermittent auscultation. There are randomised controlled trials of electronic fetal monitoring versus intermittent auscultation but no up to date studies comparing different methods of intermittent auscultation.⁽³⁾The aim of the guideline was to look at electronic fetal monitoring and not intermittent auscultation. The recommendations on the form of intermittent auscultation used are therefore based on randomised controlled trials comparing electronic fetal monitoring and intermittent auscultation, not different methods of intermittent auscultation. Many units do not have the staffing levels to achieve the level of auscultation suggested by the guideline. Thomas et al rightly state that a properly formed trial of which is the best method of intermittent auscultation needs to be done.

I agree with Murphy that the effect on intervention rates in the paper by Mires et al may be mainly due to the subsequent continuous fetal monitoring. This emphasises that continuing education in the interpretation of cardiotocography is crucial (Grant). The recognition of normality and hence the possibility of returning to intermittent auscultation where appropriate is an area that was not covered in detail by the RCOG guidelines.

I take issue with Clow in his analysis of the high risk subgroup. Such an analysis is inappropriate as all these women were monitored according to the complication, not their allocation in the study. Therefore the majority of them would have had either intermittent or continuous cardiotocography. They cannot therefore be compared according to their original allocations separate from the other cases. One might expect this group to have a comparatively high rate of problems compared to the low risk populations. It is certainly not possible to state that "the spirit of the trial was extended to this excluded group" and extrapolating this to all patients at low risk. It is unfortunate that the details of this high risk group are not included in the study to confirm that the randomisation process was adequate and that equal numbers occurred in the study groups.

Although this paper is flawed, it has stimulated this important debate, which will hopefully provide the impetus for a larger trial to answer this important question.

Ros Goddard

specialist registrar

Royal United Hospital, Bath BA1 3NG

ros_goddard{at}hotmail.com

Electronic responses. Randomised controlled trial of cardiotocography versus Doppler auscultation of fetal heart at admission in labour in low risk population. bmj.com 2001;322 (www.bmj.com/cgi/eletters/322/7300/1457#responses).
Electronic responses. Electronic fetal monitoring. bmj.com 2001;322 (www.bmj.com/cgi/content/full/322/7300/1436#responses).
Clinical Effectiveness Support Unit. The use of electronic fetal monitoring. The use and interpretation of cardiotocography in intrapartum fetal surveillance. London: Royal College of Obstetricians and Gynaecologists, 2001.