Opposite changes in carotid versus aortic stiffness during healthy human pregnancy

Systemic arterial compliance has been known to increase during healthy pregnancy, whereas, recently, the carotid artery has been reported to stiffen. To clarify this controversy, we simultaneously measured aortic PWV (pulse wave velocity) and carotid artery elastic parameters in a cohort of pregnant women. Twelve normotensive pregnant women were studied longitudinally during the three trimesters of pregnancy (T₁, T₂ and T₃ respectively) and 12 weeks PP (postpartum). Carotid artery diastolic diameter and pulsatile distension was measured by an echo-wall tracking method and carotid pulse pressure by applanation tonometry. Carotid strain, compliance, distensibility coefficient, stiffness index β, E_inc (incremental elastic modulus) and augmentation index were calculated. Aortic PWV was determined to estimate aortic distensibility. All carotid artery elastic parameters indicated significant stiffening from T₁ to T₃ (1.8±0.2 versus 2.9±0.3 mmHg for E_inc), which was reversed after delivery (2.3±0.2 mmHg). Aortic PWV decreased during pregnancy (6.2±0.2 versus 5.4±0.2 m/s) and increased in the PP period (6.7±0.2 m/s). No correlation was found between changes in carotid artery elastic parameters and changes in aortic PWV either from T₁ to T₃ or from T₃ to PP. The carotid artery exhibits regionally specific stiffening during pregnancy, which appears to represent a qualitatively different change in arterial elastic behaviour.