We are delighted with the interest from Casati & Frasch (2014) in our study of the development of the power spectrum of fetal heart rate variability (FHRV). We are confused by the call to adhere to a fetal standard when there is currently no consensus or a strong evidence base to justify a fetal range. Our goal was systematically to quantify changes in FHRV spectral power in the last third of gestation to see whether these changes could be related to the known maturation of sympathetic activity (Booth et al. 2011). The most striking finding was that there is very little high-frequency activity over the last third of gestation in the fetal sheep. This is consistent with previous reports in human pregnancy from magnetocardiogram recordings that included assessment of higher frequency activity from 0.4 to 1.7 Hz that nearly all FHR power was less than 0.2 Hz, showing that there is relatively
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