What changes occur in the components of the Renin-Angiotensin-Aldosterone System (RAAS) during pregnancy?

During pregnancy, the Renin-Angiotensin-Aldosterone System (RAAS) undergoes significant physiological changes that support maternal and fetal health. Specifically, all major components of the RAAS system, including renin, angiotensinogen, angiotensin I, angiotensin II, and aldosterone, see increases throughout pregnancy.

As pregnancy progresses, the renin levels increase due to a rise in placental production and the physiological need to maintain blood volume and perfusion to the developing fetus. Angiotensinogen, produced by the liver and its levels increase significantly during pregnancy due to hormonal influences, primarily from estrogen. This rise in angiotensinogen enhances the substrate availability for the conversion into angiotensin I and subsequently angiotensin II.

Angiotensin II, serving as a potent vasoconstrictor, plays a crucial role in regulating systemic vascular resistance and promoting sodium retention, which is vital in the context of the increased blood volume and cardiac output needed during pregnancy. Similarly, aldosterone levels are elevated to support sodium retention, which aids in expanding the extracellular fluid volume necessary for both maternal and fetal needs.

Given this context, it is clear that the overall response of the RAAS during pregnancy is characterized by an increase