RELATION BETWEEN FREQUENCY OF UTERINE CONTRACTIONS AND HUMAN FETAL CEREBRAL OXYGEN-SATURATION STUDIED DURING LABOR BY NEAR-INFRARED SPECTROSCOPY

Objective To investigate the effect of the frequency of uterine contra ctions on fetal cerebral oxygenation, using near infrared spectroscopy . Design An observational study relating changes in the fetal cerebral concentrations of oxyhaemoglobin and deoxyhaemoglobin, measured from the start of one contraction to that of the next, to the time interval between contraction peaks observed by external tocography. Setting A teaching hospital obstetric and neonatal unit. Subjects Ten term fetus es during labour. Results Changes in cerebral oxyhaemoglobin concentra tion were positively, and in deoxyhaemoglobin negatively, correlated w ith the time interval between contractions (P <0.001). A mean contract ion interval of 2.3 min was found below which the concentration of oxy haemoglobin usually fell and that of deoxyhaemoglobin rose, indicating a fall in cerebral haemoglobin saturation. Conversely, longer contrac tion intervals were associated with findings indicative of a rise in c erebral haemoglobin saturation. Conclusion Short contraction intervals (<2.3 min) were associated with a decrease, and longer contraction in tervals with an increase in fetal cerebral oxygen saturation. Contract ions occurring repeatedly at intervals less than 2.3 min are likely to result in progressive cerebral desaturation.