Venous and arterial behavior during normal pregnancy

Abstract

Physiol. 43): H1605-H1612, 1998.-To assess the contribution of the arterial and venous systems in the hemodynamic changes of normal pregnancy, we studied blood flow, vascular resistance, venous tone, and the viscoelastic properties (''creep'') of the upper and lower limbs (using plethysmography), aortic distensibility (using pulse wave velocity measurements), and cardiac dimensions (using echocardiography) in nine healthy women. Studies were longitudinally performed at the first (10-13 wk) and third (33-38 wk) trimesters of pregnancy in comparison with the period between the third and sixth month after delivery. From the first trimester, heart rate significantly increased while systemic blood pressure and limb vascular resistances did not change significantly and aortic distensibility increased (P Ͻ 0.05). Lower limb viscoelastic properties decreased at the third trimester (P Ͻ 0.05) and venous tone increased from the first trimester (P Ͻ 0.01), whereas little changes were observed at the site of upper limbs. The decrease in calf venous tone was significantly correlated with the increase in left ventricular diastolic diameter at the first (P Ͻ 0.001) and the third trimester (P Ͻ 0.05). The study provides evidence that during normal pregnancy, changes in the arterial and venous sides of the circulation occur independently of pressure alterations. The increase in venous tone, contributing to preload augmentation, and the decrease in aortic stiffness, reducing afterload, both optimize cardiac function until delivery. venous tone; aortic compliance; arterial distensibility; cardiac function IT IS WELL ACCEPTED that a normal pregnancy is characterized by a large increase in total blood volume and in cardiac output (31,32,48). Blood volume expansion appears early during the pregnancy and rises up to 50%. Cardiac output rises up to 40-50% above nonpregnant values, and the highest increase is reached halfway through gestation. Cardiac output is the product of heart rate and stroke volume. Heart rate is known to reach a 10-27% increase between weeks 4 and 36 of pregnancy (10). However, an increase in stroke volume might also play an important role at the early phase. Stroke volume appears elevated at least until weeks 28-32 (31). The mechanism(s) causing the increase in stroke volume are not yet well established. In pregnant rats and women, an increased cardiac contractility has been suggested (13,36,44), but the differentiation between the contractile properties of cardiac muscle itself and the contractile changes that result from altered preload and afterload is difficult to establish. The possibility should be considered that an increase in venous return also plays a major role. In the literature, numerous data indicate a significant increase in venous capacitance (11,17,18,28,35,47). However, significant discrepancies have also been reported, depending mainly on the site of measurement of venous variables (40, 46). Furthermore, the early venous changes could not be adequately detected because pregnant women were not ...

Influence of the Menstrual Cycle, Pregnancy, and Preeclampsia on Arterial Stiffness

“…29 Other studies report no change in PWV with gestation 30 or a general decrease in PWV and augmentation index during pregnancy. 6,8,9,11 All of these studies had limited and wide time points, with the third-trimester visits performed earlier than in our study. These limitations may potentially explain why the subtle rise in PWV and augmentation index in the third trimester went undetected in these studies.…”

Influence of hyperglycemia during and after pregnancy on postpartum vascular function

“…During a normal pregnancy, aortic PWV has been found to increase (18,30,32) or remain unchanged (24) with increasing gestation. Women affected by GDM exhibit a marginally increased PWV compared with non-GDM women in the third trimester (40).…”

“…Women affected by GDM exhibit a marginally increased PWV compared with non-GDM women in the third trimester (40). After delivery, aortic PWV has been found to increase but has not been compared with nonpregnant women to determine whether these values return to prepregnant/nonpregnant values (18,30,32). In contrast, upper limb PWV appears unaffected by increasing gestation, suggesting a differential effect on central elastic (aorta) and peripheral muscular (brachial) arteries (24).…”

Maternal Wave Reflections and Arterial Stiffness in Normal Pregnancy as Assessed by Applanation Tonometry

“…[1][2][3][4] The decrease in peripheral vascular resistance and generalized vasodilation is associated with increased aortic distensibility. 5,6 However, there is scanty information regarding maternal central hemodynamics and arterial stiffness. Noninvasive assessment of arterial stiffness is possible by the simple, validated, and reproducible technique of applanation tonometry.…”