LATE FETAL HEART DECELERATIONS AND CHANGES IN CEREBRAL OXYGENATION DURING THE FIRST STAGE OF LABOR

Objective To test the hypothesis that late fetal heart rate decelerati ons are associated with a decrease in cerebral oxygenation. Design Cha nges in fetal cerebral concentrations of oxyhaemoglobin and deoxyhaemo globin were measured by near infrared spectroscopy, before, during and after contractions with late fetal heart rate decelerations and compa red with changes during contractions with no alteration of heart rate. Setting Teaching hospital obstetric unit. Subjects Ten women in labou r at term. Results The changes in fetal cerebral oxyhaemoglobin and de oxyhaemoglobin concentrations that occurred during contractions were q uantitatively similar, irrespective of the fetal heart rate changes. H owever, late fetal heart rate decelerations were associated with a sig nificantly greater fall, after the uterine contraction, in the mean co ncentration of fetal cerebral oxyhaemoglobin of 0.52 mu mol/100 g (SD 0.25) (P < 0.001) and a significantly greater rise in the mean concent ration of deoxyhaemoglobin of 0.36 mu mol/100 g (SD 0.35) (P < 0.01). Conclusion Late fetal heart rate decelerations are associated with a s ignificant decrease in cerebral oxygenation.