Hormones and hemodynamics in pregnancy

Area of Science:

• Physiology
• Reproductive Biology
• Cardiovascular Science

Background:

• Normal pregnancy is characterized by sodium and water retention, leading to plasma volume expansion.
• Pregnancy is thought to involve a 'resetting' of volume and osmoreceptors.

Purpose of the Study:

• To explain the mechanisms behind the 'resetting' of volume and osmoreceptors in pregnancy.
• To investigate the earliest hemodynamic changes in pregnancy and their consequences.

Main Methods:

• Analysis of human pregnancy studies focusing on hemodynamic changes.
• Examination of the role of the neurohumoral axis, including the renin-angiotensin-aldosterone system.
• Assessment of endothelial nitric oxide synthase activity and arterial vasodilation.

Main Results:

• The earliest hemodynamic change in pregnancy is primary systemic arterial vasodilation.
• This vasodilation leads to increased cardiac output and activation of the neurohumoral axis.
• Increased endothelial nitric oxide synthase activity contributes to resistance to pressor effects.

Conclusions:

• Systemic arterial vasodilation is a primary event in normal pregnancy adaptation.
• Reversal of this vasodilation, without appropriate neurohumoral activation, can lead to preeclampsia.
• Decreased renal vasodilation is linked to reduced glomerular filtration rate in preeclampsia.