Diurnal variations of short-term variation and the impact of multiple recordings on measurement accuracy

Objective: Short-term variation (STV) from computerized cardiotocogram heart rate analysis is a parameter that complements decision making, regarding the delivery of fetuses in several high-risk situations. Although studies on the effects of gestational age and fetal pathology are convincing, there is a lack of data exploring diurnal variation and the adequacy of a single measurement. Study Design: In this prospective observational study, fetal STV was monitored with the AN24 fetal ECG monitor (Monica Healthcare) each hour for at least 10 h in total, beginning at different times. This resulted in data covering all 24 h of the day. Seventy fetuses, low risk with respect to conditions accessible to heart rate monitoring (median 37th week of gestation) were monitored for an average of 12 h. Results of STV per hour were categorized as ‘compromised’ (STV