Changes in cerebral autoregulation in the second half of pregnancy and compared to non-pregnant controls.

OBJECTIVE: The mechanism by which pregnancy affects the cerebral circulation is unknown, but it has a central role in the development of neurological complications in preeclampsia, which is believed to be related to impaired autoregulation. We evaluated the cerebral autoregulation in the second half of pregnancy, and compared this with a control group of healthy, fertile non-pregnant women.

METHODS: In a prospective cohort analysis, cerebral blood flow velocity of the middle cerebral artery (determined by transcranial Doppler), blood pressure (noninvasive arterial volume clamping), and end-tidal carbon dioxide (EtCO2) were simultaneously collected for 7min. The autoregulation index (ARI) was calculated. ARI values of 0 and 9 indicated absent and perfect autoregulation, respectively. ANOVA and Pearson's correlation coefficient were used, with p<0.05 considered significant.

RESULTS: A total of 76 pregnant and 18 non-pregnant women were included. The ARI did not change during pregnancy, but pregnant women had a significantly higher ARI than non-pregnant controls (ARI 6.7±0.9 vs. 5.3±1.4, p<0.001). This remained significant after adjusting for EtCO2 (p<0.001).

CONCLUSION: Cerebral autoregulation functionality is enhanced in the second half of pregnancy, when compared to non-pregnant fertile women, even after controlling for EtCO2. The autoregulation does not change with advancing gestational age.