Intermittent Auscultation or Intermittent FHR surveillance?
The question may sound strange. IA is an old term when fetal heart rate
(FHR) could only be listened to and counted with stethoscope. Moreover,
the very early hand-held Doppler-devices produced only audible tones but
no numerical readout of FHR. But for the last 25 years the
Doppler-devices continuously display the instantaneous FHR as beats per
minute. Hence, this very basic facility means that it is not a must to
actually count the fetal heart tones anymore, even if or just because we
continue to use the old term ‘auscultation’. Is it really worth changing
the terminology of IA to something like ‘intermittent FHR
surveillance/observation’? Thus, the idea that IA must involve the skill
in listening and actually counting sounds9,10 is
out-dated and best discarded. For example, a proposed ‘intelligent IA’
states, “In conclusion, the recommendation should be to listen for at
least a full minute and count the baseline, the steady rate, but listen
for accelerations and decelerations.” A bit of detailed consideration
reveals this foundational recommendation to be full of contradictions
(hence void). If one actually counts for one minute, it is not possible
to know in advance whether one is starting with a late deceleration or
one is going to encounter an acceleration. Moreover, after ‘listening’
to a deceleration or acceleration, only a part of the one minute (not
counted separately) would be the ‘steady rate i.e. the baseline’. Then
one has not really counted the steady rate separately at all but only
the average rate over the full one minute (including the
acceleration/deceleration). Extending beyond one minute would require
restarting the count from zero again and deciding when to stop counting
(when will one be satisfied that one has managed to count the steady the
steady rate separately, how?). It is far more accurate, reliable and
convenient to simply watch the FHR numerical display on the
Doppler-device and observe the FHR figure accelerate or decelerate
(approximately how much as well) or remain steady during the entire or
part of the duration of auscultation (a minute or flexibly more as much
as required).6 One can decide which part of the
observation showed the steady FHR most likely to represent the baseline.
In presence of late decelerations or accelerations, the baseline rate is
likely to be observed a bit before or during early part of the
contraction.6 Many guidelines (wrongly) persist with
the preoccupation of actually counting the fetal heart
tones1,2; while the WHO guidelines11ambiguously mention, “Each auscultation should last at least 1 minute;
if the FHR is not always in the normal range (I.e. 110-160bpm),
auscultation should be prolonged to at least three contractions.”
Clearly, the paradox is that one can confirm FHR to be always in the
110-160 range during the auscultation period only by looking at the
actual numerical FHR display on the Doppler-device or by a complicated
‘multiple count strategy’4 but not at all by simply
counting the fetal heart tones for 1 minute or more.