Doppler-device versus Pinard stethoscope: Evidence from RCTs
In addition to the practically perceived accuracy, the hand-held Doppler-device has additional advantages of ease, simplicity and reassurance to the mother of hearing the fetal heart sounds. Why do then guidelines 1-4,11 maintain that that the Doppler-device or Pinard are equally preferable? Indeed, a systematic scoping review of many aspects of IA was unhelpful for practice improvement but highlighted only one conclusion namely “there was no evidence to recommend Doppler-device instead of Pinard”.7 But is this sole conclusion valid? Is the evidence judiciously interpreted and then appropriately applied? Does statistics often leads scientists to deny differences that are clear to see or experience?8,19
There are four RCTs of “Doppler vs Pinard” including 8436 women, all from African countries.7,20-23 In three studies the facility of CTG was not available/used at all.20-22 In contrast, CTG is the recommended recourse after abnormal IA in developed countries to optimise perinatal outcome.1-4 Only one study 23 from a teaching university hospital had CTG facility available (for a separate group); but it appears that the Doppler and Pinard groups did not have CTG after detection of abnormalities on IA. The perinatal outcome was much worse in the Pinard than in the Doppler group (neonatal convulsions 6 vs 0, hypoxic encephalopathy 7 vs 1, perinatal mortality 5 vs 2), but the differences were not statistically significant due to small patient numbers (312 and 310) in the two groups.23 Most importantly all four study protocols only required detection of FHR baseline in the abnormal range (<120 or >160 beats/minute); but the detection of late decelerations was not required/advised.20-23 This was indeed the standard recommendation by the World Health Organisation (WHO) when these RCTs were performed.24 This recommendation has only recently been upgraded by the WHO 11 to include decelerations thus making these RCTs 20-23 outmoded. The main perceptible advantage of Doppler-device is the improved detection of FHR decelerations. Thus, for reasons above it can be concluded that the results from these African RCTs7,20-23 cannot be extrapolated to the obstetric practice in developed countries.