Sympathetic Neural Activity During Early Pregnancy in Women with Prior Gestational Hypertension and Preeclampsia

Abstract

Background Sympathetic overactivity likely plays a role in the primary manifestation of gestational hypertension and preeclampsia, and may contribute to the substantially-elevated risk for recurrence in women with a history of the disorders. We tested the hypothesis that women with a history of hypertensive pregnancy would have augmented neural activity prior to and during the early phase of a subsequent pregnancy. Methods: Healthy women with (HP+; n= 8) and without (CON; n = 8) a history of hypertensive pregnancy were tested prior to (PRE, mid-luteal phase) and during EARLY (4-8 weeks) pregnancy. Heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressure, and muscle sympathetic nerve activity (MSNA) were measured during 6 min of supine rest, followed by 6 min of 60° head-up tilt (HUT). Results: There were no group differences in supine or HUT HR, SBP, or DBP at either PRE or EARLY. Supine and HUT MSNA tended to be higher in HP+ compared to CON during PRE (p = 0.098). During EARLY, supine MSNA increased from PRE in both groups (p < 0.001) and tended to be greater in HP+ than CON (28 ± 9 vs. 20 ± 9 bursts·min-1; p = 0.11); however, HP+ women had an attenuated increase in MSNA from supine to HUT (ΔMSNA: 15 ± 7 vs. 26 ± 9 bursts·min-1; p = 0.014). Conclusions Despite similar hemodynamic responses, HP+ women appear to have elevated MSNA at rest but attenuated sympathetic responses to upright tilt during early pregnancy, compared to healthy women. A “ceiling” effect (a reduced sympathetic reserve during tilting) and/or decreased sympathetic baroreflex sensitivity may be the underlying mechanism(s).