Normal pregnancy is associated with enhanced endothelium-dependent flow-mediated vasodilation

Area of Science:

• Cardiovascular Physiology
• Reproductive Medicine
• Endothelial Function

Background:

• Normal pregnancy involves decreased systemic vascular resistance, potentially mediated by nitric oxide (NO).
• Endothelial vasomotor function is crucial for regulating vascular tone during pregnancy.

Purpose of the Study:

• To compare endothelial vasomotor function in normal pregnant women across trimesters versus nonpregnant controls.
• To investigate the role of nitric oxide (NO) in mediating vascular changes during pregnancy.

Main Methods:

• Ultrasound assessment of brachial artery diameter at rest and during reactive hyperemia (flow-mediated dilation, FMD).
• Measurement of endothelium-independent dilation using nitroglycerin.
• Comparison of 71 pregnant women (by trimester) with 37 healthy nonpregnant controls.
• Longitudinal evaluation of eight women throughout pregnancy.

Main Results:

• Pregnant women showed increased resting flow and brachial artery diameter in mid and late trimesters.
• Flow-mediated dilation (FMD) significantly increased throughout pregnancy, peaking in the last trimester (47% above nonpregnant values).
• Nitroglycerin-induced dilation was similar between pregnant and nonpregnant groups, indicating preserved smooth muscle function.

Conclusions:

• Basal and stimulated nitric oxide (NO) activity is enhanced in normal pregnancy.
• Increased FMD throughout pregnancy contributes to the reduction in peripheral vascular resistance.
• Endothelial function is significantly altered and enhanced during normal pregnancy.