Introduction
Intermittent auscultation (IA) of fetal heart rate (FHR) is approved for fetal monitoring in low-risk labours in most developed countries.1-4 In the UK it is expected that up to 50% of women may have IA.1 However, IA as well as cardiotocography (CTG) are often criticized as ‘evidence free zones.’ Consequently, a small number of sceptics demand abandonment of CTG itself, 5 not a practical prospect for very good/valid reasons. There are many more detractors of IA (personal communications) who question the few randomised controlled trial (RCTs) showing equivalent outcomes with IA and CTG. The gold standard of evidence in medicine remains RCTs. But, very large studies required for definitive guidance for IA are unlikely to come. As a result, there has been proliferation of several different regimes of IA.1-4Instances of serious intrapartum asphyxia continue to occur despite complying with the recommended regimes 6 highlighting the scope and need for improvements. A recent comprehensive systematic review of 26 studies and 11 guidelines concluded that the optimal regime of IA (frequency, duration, method) remains unproven.7Similarly, many other systematic analyses have failed to provide practical suggestions for improvement.6
Empiricism remains at the heart of science and statistics is said to be its grammar. Interestingly, ‘thought experiments’ have contributed to many major advances, not just in physics. Critical thinking is now considered at least as important as the statistical tests.8 This review is not based on anecdotes but evaluates IA regimes and possible improvements by detailed modelling and reasoning, consistent with methods adopted in many consensus guidelines.1-4 Any evidence when available is supplemented with experience and observational knowledge gained from CTG. The focus is on the actual method of IA only. Other aspects of IA are outside the remit. Some of the discussion may appear very simple, obvious and intuitive, but still needs to be presented for reflection and bringing about practical improvements.