Longitudinal study of cerebral blood flow regulation during exercise in pregnancy.

Cerebrovascular adaptation to pregnancy is poorly understood. We sought to assess cerebrovascular regulation in response to visual stimulation, hypercapnia and exercise across the three trimesters of pregnancy. Using transcranial Doppler (TCD) ultrasound, middle and posterior cerebral artery mean blood velocities (MCAv and PCAv) were measured continuously at rest and in response to (1) visual stimulation to assess neurovascular coupling (NVC); (2) a modified Duffin hyperoxic CO rebreathe test, and (3) an incremental cycling exercise test to volitional fatigue in non-pregnant ( = 26; NP) and pregnant women (first trimester [ = 13; TM1], second trimester [ = 21; TM2], and third trimester [ = 20; TM3]) in total 47 women. At rest, MCAv and PCO were lower in TM2 compared to NP. PCAv was lower in TM2 but not TM1 or TM3 compared to NP. Cerebrovascular reactivity in MCAv and PCAv during the hypercapnic rebreathing test was not different between pregnant and non-pregnant women. MCAv continued to increase over the second half of the exercise test in TM2 and TM3, while it decreased in NP due to differences in ΔPCO between groups. Pregnant women experienced a delayed decrease in MCAv in response to maximal exercise compared to non-pregnant controls which was explained by CO reactivity and PCO level.