Re: “Sinusoidal‐like fetal heart‐rate pattern” real‐time ultrasound may help in differential diagnosis

We read with interest the above article (1) in your journal and we would like to emphasise the accepted definition of the sinusoidal pattern based on number of reports in the literature and also would like to suggest a simple alternative to help in differential diagnosis. A sinusoidal heart rate pattern should have a stable baseline rate of 120 to 160 bpm with regular oscillations; amplitude of 5 to 15 bpm, rarely greater; frequency of 2 to 5 cycles per min; fixed or flat short term variability; oscillation of the sinusoidal wave form above and below a baseline; no areas of normal fetal heart rate (FHR) variability or reactivity (2). Though the traces described (1) may be called sinusoidal-like, most of them could be ruled out as not sinusoidal by the presence of reactive segments seen in the trace without the need to resort to real-time ultrasound. It is proposed that when encountered with a sinusoidal-like FHR pattern real-time ultrasound may help by identifying the rhythmic fetal mouth movements which are associated with such patterns (3). Such equipment or expertise may not be available at all times and in all centres. Vibro-acoustic stimulation of the fetus is a simple, easily applicable alternative. FHR accelerations can be provoked with this stimuli making it a reactive trace. It is known that fetal and neonatal outcome are the same in a fetus with spontaneous or sound provoked reactivity (4). This has been our practice over the last few years when such a trace is encountered and we have had no adverse outcome. Repeat FHR tracing after a few hours or the next day invariably reveals a reactive trace with no sinusoidallike fetal heart rate pattern.