Maternal Physical Activity Is Associated With Improved Blood Pressure Regulation During Late Pregnancy

Background: Cardiovagal baroreflex gain (cBRG) reflects an individual's ability to buffer swings in blood pressure. It is not well understood how this mechanism is influenced by physical activity in pregnancy. Because pregnant women tend to engage in low levels of moderate-to-vigorous physical activity (MVPA) and high levels of sedentary behaviour, we sought to determine the influence of MVPA and sedentary behaviour on cBRG and mean arterial pressure (MAP) in pregnancy. Methods: Fifty-eight third trimester (31.9 +/- 3.0 weeks) normotensive pregnant women (31.2 +/- 2.8 years) were tested. Heart rate (electrocardiogram) and blood pressure (systolic blood pressure and MAP; finger photoplethysmography) were collected on a beat-by-beat basis, and averaged over 3 minutes of rest. Spontaneous cBRG was calculated as the slope of the relationship between fluctuations in systolic blood pressure and heart rate. Objective measures of MVPA and sedentary behaviour were collected over a 7-day period using an ActiGraph accelerometer (model wGTX3-BT; ActiGraph LLC, Pensacola, FL). Results: Participants spent 67.5 +/- 7.9% of waking hours engaged in sedentary behaviour, and performed 68.6 +/- 91.9 minutes of MVPA per week. Sedentary behaviour was not related to cBRG (r = -0.035; P = 0.793) or MAP (r = -0.033; P = 0.803). However, MVPA was positively associated with cBRG (r = 0.315; P = 0.016), but not MAP (r = -0.115; P = 0.389). The association between MVPA and cBRG remained significant after controlling for age, pre-pregnancy body mass index, gestational age, and wear time (r = 0.338; P = 0.013), indicating that women who engaged in greater amounts of MVPA showed increased cBRG. Conclusions: Our data suggest that increased MVPA, but not necessarily reduced sedentary behaviour, might be beneficial for reflex control of blood pressure during pregnancy.