The effect of maternal pushing on fetal cerebral oxygenation and blood volume during the second stage of labour.

OBJECTIVE

To measure the effect of maternal pushing during the second stage of labour on fetal cerebral oxygenation and blood volume.

DESIGN

A prospective study comparing changes in the fetal cerebral concentrations of oxyhaemoglobin, deoxyhaemoglobin and cerebral blood volume, before and during maternal pushing in the second stage of labour.

SETTING

Teaching hospital obstetric unit.

SUBJECTS: Ten term fetuses during labour.

RESULTS

Following the onset of maternal pushing, mean cerebral deoxyhaemoglobin concentration increased by a mean of 0.79 (SD 0.59) mumol.100 g-1, (P < 0.01) without any consistent change in the oxyhaemoglobin concentration. These changes were associated with a significant decrease in the calculated mean cerebral oxygen saturation from a mean of 46.8% (SD 8.6) to 38.1% (SD 5.2) (P < 0.01). Pushing was also associated with a significant increase in the mean cerebral blood volume, which rose by a mean of 0.33 ml.100 g-1 (SD 0.37) (P < 0.05).

CONCLUSION

Maternal pushing during the second stage of labour leads to a significant decrease in fetal cerebral oxygenation, together with an increase in cerebral blood volume.