Figure 3 (Illustration 3)
Schematic illustration of IA of FHR with acceleration: An acceleration can be inferred when a rise of FHR of 15 bpm or more is observed on Doppler-device display, preceded by a normal FHR baseline and return to it after the acceleration. This is difficult to detect precisely/subjectively while counting fetal heart beats over a minute with Pinard stethoscope. The total count over 1 minute spuriously gives an abnormally high figure (170 bpm) instead of a true baseline of 155 bpm. Even the cumbersome ‘multiple count strategy’4 is less accurate than simply observing the numerical FHR display on the Doppler-device.