The sympathetic nervous system in normotensive and hypertensive pregnancies

Pregnancy is associated with significant physiological adaptations that facilitate optimal foetal development and growth. Among the most notable changes in healthy pregnancies are increases in plasma volume, cardiac output, and sympathetic nervous system activity, alongside a reduction in total peripheral resistance. Normotensive pregnancies are among the few physiological states in which elevated sympathetic activity is considered normal and beneficial. However, the underlying mechanisms that reconcile this increase in SNA with the concomitant decrease in blood pressure remain incompletely understood. In contrast, excessive sympathetic activity, beyond the expected pregnancy-associated increase, has also been implicated in the pathophysiology of hypertensive disorders of pregnancy, such as gestational hypertension and preeclampsia, which are major contributors to maternal and foetal morbidity and mortality. This review aims to provide an overview of the current understanding of the physiological and pathophysiological mechanisms underlying both normotensive and hypertensive pregnancies.