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 decelerations are associated with a decrease in cerebral oxygenation. Design Changes in fetal cerebral concentrations of oxyhaemoglobin and deoxyhaemoglobin were measured by near infrared spectroscopy, before, during and after contractions with late fetal heart rate decelerations and compared with changes during contractions with no alteration of heart rate. Setting Teaching hospital obstetric unit. Subjects Ten women in labour at term. Results The changes in fetal cerebral oxyhaemoglobin and deoxyhaemoglobin concentrations that occurred during contractions were quantitatively similar, irrespective of the fetal heart rate changes. However, late fetal heart rate decelerations were associated with a significantly greater fall, after the uterine contraction, in the mean concentration 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 concentration 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 significant decrease in cerebral oxygenation.