Longitudinal changes in cardiovascular and sympathetic neural responses to static handgrip exercise throughout pregnancy.

Backgrounds: The time-course changes in the exercise pressor response throughout gestation remain unknown. As pregnancy is associated with altered hemodynamics and sympathetic activation, we hypothesized that neural responses to static handgrip (SHG) exercise would be augmented, especially during late pregnancy. Methods: Forty-six women (30±6 yrs [SD]) were studied longitudinally during early and late pregnancy, and postpartum. Mean arterial pressure (MAP), cardiac output (Qc), total peripheral resistance (TPR=MAP/Qc) and muscle sympathetic nerve activity (MSNA) were measured during supine rest and SHG at 40% of maximal voluntary contraction force until fatigue, followed by 2-min post-exercise circulatory occlusion (PECO) to isolate muscle metaboreflex activation. Results: The peak increase (Δ) in MAP during fatiguing SHG did not differ among gestation stages (P=0.669), but ΔMAP during PECO trended smaller in late pregnancy than postpartum (P=0.054). ΔQc during SHG and PECO was larger in late pregnancy compared to early pregnancy and postpartum (P<0.05), while ΔTPR was lower in late pregnancy (P<0.05). ΔMSNA during SHG was not different (P=0.740) but smaller during PECO in late pregnancy compared to early pregnancy and postpartum (P<0.05). Confounding factors like obesity or pregnancy complications did not affect these responses (P>0.05). Conclusion: Sympathetic activation elicited by the muscle metaboreflex was reduced in late pregnancy, which may be related to the blunted peripheral vasoconstriction. Conversely, the cardiac output response to exercise was augmented in late pregnancy. These results suggest that central and peripheral responses are impacted differently to maintain an adequate pressor response to exercise throughout pregnancy, regardless of obesity and complications.