[Intrapartum fetal heart rate changes during baseline T/QRS rise events in acidotic fetuses]

Our objective was to assess the association between fetal heart rate (FHR) and the amplitude of baseline T/QRS rise events during labour in normal and acidotic fetuses.

Into a retrospective case-control setting, we analyzed STAN traces from acidotic (pH < 7.05, n = 39) and normal fetuses (n = 33) at birth, with baseline T/QRS rise type ST-event in fetal electrocardiogram. Mean FHR was computed over a 2-minute period associated with baseline T/QRS rise event. We described a control FHR segment, 10 minutes before first occurrence of baseline T/QRS rise event. We compared the mean FHR from ST-events, with data from control segment, in relation to the amplitude of T/QRS rise, for acidotic and normal fetuses.

We found that, during the increase in the baseline of T/QRS, the mean frequency gradually and significantly decreased. This was quick and deep in normal fetuses and small, followed by a plateau, till high T/QRS values for acidotic group. However, for high T/QRS values, both groups had similar decreased values.

We conclude that changes of FHR related to increase of T/QRS baseline are less pronounced in fetuses dealing with acidosis, probably due to activation of sympathetic system. This should enable us to intervene in the appropriate manner when the fetal defenses have been activated but before there is an increased risk of long-term squeals.