Objective: To measure the effect of changes in maternal posture on fetal cerebral oxygenation during normal labour.
Design: A prospective study comparing changes in the fetal cerebral concentrations of oxyhaemoglobin, deoxyhaemoglobin and cerebral blood volume, measured by near infrared spectroscopy, in women with effective epidural analgesia when moved from the left lateral to the supine position during labour.
Setting: A London teaching hospital obstetric unit.
Subjects: Fourteen women during uncomplicated labour at term.
Results: When compared with the left lateral position, the supine position was associated with a significant decrease in the mean concentration of fetal cerebral oxyhaemoglobin of 1.12 (SD 1.0, 95% CI 0.49 to 1.75) mumol. 100 g-1 (P < 0.01) without any significant change in the mean concentration of deoxyhaemoglobin and cerebral blood volume. These changes were associated with a significant decrease in the mean cerebral oxygen saturation of 8.3 (SD 8.8, 95% CI 1.5 to 15.1)% (P < 0.05, n = 9).
Conclusion: Changes in maternal posture during labour, in women with effective epidural analgesia, are associated with a significant decrease in fetal cerebral oxygenation.