Hypotension due to spinal anesthesia influences fetal circulation in primary caesarean sections

Hypotension due to spinal anesthesia is a well-known side effect in pregnant women receiving caesarean section. Little is known about its impact on fetal blood circulation.

40 women with uncomplicated singleton term pregnancies prepared for caesarean section were prospectively evaluated by Doppler sonography before and immediately after spinal anesthesia.

In 90% of the women, blood pressure significantly decreased after spinal anesthesia and 42.5% of the patients suffered from severe hypotension. We found a significant negative correlation between maternal blood pressure change and the resistant index (RI) of the umbilical artery (r_s = - 0.376, p = 0.017) and a significant positive correlation between maternal blood pressure and fetal middle cerebral artery.

Healthy fetuses seem to compensate well in situations with decreased uteroplacental blood flow due to maternal hypotension measured by means of RI changes in the fetal umbilical and middle cerebral artery. This raises the question if growth-restricted and/or preterm fetuses are able to compensate similarly or if general anesthesia would be a method of choice.