Correlation of Intrapartum Changes in Fetal Heart Rate with Fetal Blood Oxygen and Acid-Base State

The intrapartum deceleration in center stage: a physiologic approach to the interpretation of fetal heart rate changes in labor

“…However, as the occlusion is continued, decelerations are maintained by direct hypoxic myocardial depression. 35 Consistent with a role of reduced myocardial vagal tone in the overshoot pattern, atropine produces overshoot tachycardia both in the human 7,85 and the fetal sheep. 36 Catecholamine stimulation must also be required, since the FHR overshoot induced by atropine can be abolished by concurrent administration of propranolol.…”

“…6 Caldeyro-Barcia described Type 1 dips occurring with the contraction and Type 2 dips occurring after the contraction. 7 The brief shallow decelerations originally described by Hon as 'early' decelerations have mystified some clinicians who claim that early decelerations occur very infrequently, if at all. We believe the reason for this discrepancy lies in the paper speed at which the FHR is recorded.…”

Characteristics of fetal heart rate changes during the expulsive stage of bovine parturition in relation to fetal outcome

“…in 7 calves , it remained stable , whereas in the remaining 7 calves it was increased . In contrast , baseline FHR increased in 14 AC calves and remained stable in only 2 calves . These differences between the N -AC and AC groups were statistically significant (P < 0.03 ).…”

“…Comparable definitions for these characteristics of decelerations are used to describe decelerations in CTG obtained from human fetuses. 7,12,14 Slow recovery of the deceleration , presence of overshoot , and smoothing after the deceleration are additional characteristics of variable decelerations in CTG recordings.4.15 Slow recovery of a deceleration is defined as a recovery phase of longer duration than the decrease in FHR from baseline to the nadir of the deceleration . Overshoot is a secondary and marked increase in heart rate beyond com- Baseline FHR is defined as the mean FHR between contractions and in the absence of periodic alterations of the FHR.11,18 The A-FHR is defined as the difference between baseline FHR during the actual window and that during the first window (window -10 ) .…”