Studies on the Circulation in Pregnancy. I. The Velocity of Blood Flow and Related Aspects of the Circulation in Normal Pregnant Women 1

Cohen, Mandel E.; Thomson, Kate

doi:10.1172/jci100813

Cited by 40 publications

(4 citation statements)

References 19 publications

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“…Ccrcbral circulation seems to remain unchanged (McCall 1949). The reports on circulation times (arm-to-tongue, arm-to-lung) are very contradictory: Greenstein & Clahr (1 937) found an increase, Cohen & Thomson (1936) and Manchester & Loubc (1946) a slight decrease-but with values still within the range for non-pregnant adults-and Wright et al (1950) found no change. The absence of significant changes in mcan blood flow velocity in thc carotid artery corresponds to the latter findings.…”

Section: Discussionmentioning

confidence: 97%

Blood flow velocity waveforms in large maternal and uterine vessels throughout pregnancy and postpartum: a longitudinal study using Duplex sonography

Baumann

Kirkinen

Mueller

et al. 1988

BJOG

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Blood flow velocity waveforms in large maternal and uterine vessels were measured longitudinally from 16 weeks gestation onwards until 12 weeks postpartum in 21 singleton pregnancies by duplex sonography. In the maternal carotid artery, time average mean velocity (TAVmean) did not show significant changes. In both the femoral artery and vein, however, significant changes were observed. In the femoral artery, TAVmean and systolic maximum velocities decreased with advancing gestation. In the femoral vein, TAVmean remained constant throughout pregnancy and was lower than postpartum. The resistance index in the uterine arteries decreased with advancing gestation and increased after delivery. Among many factors contributing to femoral arterial blood flow velocity changes in pregnancy, we suggest that a major one is the increase in uterine blood flow. Reduction in venous femoral blood flow velocity and increase in the femoral vein diameter might be associated with the common occurrence of venous disorders in pregnancy.Numerous studies have investigatcd maternal central cardiovascular haemodynamics in pregnancy. Though different measurement methods have been used, and though many results arc controversial, it 1s generally agreed that cardiac

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Section: Discussionmentioning

confidence: 97%

Blood flow velocity waveforms in large maternal and uterine vessels throughout pregnancy and postpartum: a longitudinal study using Duplex sonography

Baumann

Kirkinen

Mueller

et al. 1988

BJOG

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“…The increases in packed cell volume and plasma viscosity during the third trimcstcr would be expected to cause an increase in blood viscosity. Previous studies of blood viscosity have only been performed at high shear rates and havc in general found a slight increase during the third trimester (Cohen & Thomson 1936;Hamilton 1950;Ruchan & Macdonald 1981). In thc present study blood viscosity was measured at both high and low shear rates, with and without correction to a standard packed cell volume (a procedure that allows study of the contribution of other determinants of blood viscosity).…”

Section: Discussionmentioning

confidence: 99%

Blood viscosity and haemostatic factors in late pregnancy, pre‐eclampsia and fetal growth retardation

Thorburn

Drummond

Whtgham

et al. 1982

BJOG

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Summary. Blood viscosity and several of its determinants (packed cell volume, plasma viscosity, plasma fibrinogen and erythrocyte deformability) and several haemostatic variables (platelet count, serum fibrin degradation products and plasma soluble fibrin) were measured in 106 women during normal third‐trimester pregnancy, 12 patients with moderate pre‐eclampsia, nine patients with severe pre‐eclampsia and 16 patients with confirmed fetal growth retardation. Blood viscosity was measured at high and low shear rates (94.5 and 0.94 s−1), with and without correction to a standard packed cell volume of 0.45. In normal pregnancy low‐shear blood viscosity increased significantly towards term, associated with significant increases in packed cell volume and plasma viscosity (but not fibrinogen); there was no change in high‐shear blood viscosity at native packed cell volume and a decrease in viscosity after correction for packed cell volume, associated with a significant increase in erythrocyte deformability. Significant decrease in the platelet count and significant increases in serum fibrin degradation products and plasma soluble fibrin suggested a degree of haemostatic activation in normal third‐trimester pregnancy. In moderate pre‐eclampsia blood viscosity was significantly lower at low shear rate, due to a significantly lower packed cell volume and despite a significantly elevated plasma viscosity. In severe pre‐eclampsia high‐shear blood viscosity was significantly elevated after correction for packed cell volume, associated with a significantly reduced erythrocyte deformability; plasma fibrinogen levels were reduced, but other variables were not significantly abnormal. In fetal growth retardation blood viscosity was significantly increased at both shear rates, despite a reduced packed cell volume: this was also associated with a significant reduction in erythrocyte deformability. In general there was little correlation between blood viscosity factors and haemostatic variables, but in normal‐term pregnancy soluble fibrin levels correlated with blood viscosity at both shear rates. We suggest that increased blood viscosity and decreased erythrocyte deformability may play a role in the placental insufficiency of severe pre‐eclampsia and fetal growth retardation.

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“…An example of the latter is the growing uterus, with cranial shift of viscera as its principal mechanical effect (1). The combination of these factors progressively influences the geometry and the dimensions of the chest wall in terms of increasing subcostal angle as well as thoracic and abdominal perimeters (15,16,26,41,61).…”

Section: Introductionmentioning

confidence: 99%

Adaptation of lung, chest wall, and respiratory muscles during pregnancy: preparing for birth

LoMauro

Aliverti

Frykholm

et al. 2019

Journal of Applied Physiology

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A plethora of physiological and biochemical changes occur during normal pregnancy. The changes in the respiratory system have not been as well elucidated, in part because radioimaging is usually avoided during pregnancy. We aimed to use several noninvasive methods to characterize the adaptation of the respiratory system during the full course of pregnancy in preparation for childbirth. Eighteen otherwise healthy women (32.3 ± 2.8 yr) were recruited during early pregnancy. Spirometry, optoelectronic plethysmography, and ultrasonography were used to study changes in chest wall geometry, breathing pattern, lung and thoraco-abdominal volume variations, and diaphragmatic thickness in the first, second, and third trimesters. A group of nonpregnant women were used as control subjects. During the course of pregnancy, we observed a reorganization of rib cage geometry, in shape but not in volume. Despite the growing uterus, there was no lung restriction (forced vital capacity: 101 ± 15% predicted), but we did observe reduced rib cage expansion. Breathing frequency and diaphragmatic contribution to tidal volume and inspiratory capacity increased. Diaphragm thickness was maintained (1st trimester: 2.7 ± 0.8 mm, 3rd trimester: 2.5 ± 0.9 mm; P = 0.187), possibly indicating a conditioning effect to compensate for the effects of the growing uterus. We conclude that pregnancy preserved lung volumes, abdominal muscles, and the diaphragm at the expense of rib cage muscles. NEW & NOTEWORTHY Noninvasive analysis of the kinematics of the chest wall and the diaphragm during resting conditions in pregnant women revealed significant changes in the pattern of thoracoabdominal breathing across the trimesters. That is, concomitant with the progressive changes of chest wall shape, the diaphragm increased its contribution to both spontaneous and maximal breathing, maintaining its thickness despite its lengthening due to the growing uterus. These results suggest that during pregnancy the diaphragm is conditioned to optimize its active role provided during parturition.

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Studies on the Circulation in Pregnancy. I. The Velocity of Blood Flow and Related Aspects of the Circulation in Normal Pregnant Women 1

Cited by 40 publications

References 19 publications

Blood flow velocity waveforms in large maternal and uterine vessels throughout pregnancy and postpartum: a longitudinal study using Duplex sonography

Blood flow velocity waveforms in large maternal and uterine vessels throughout pregnancy and postpartum: a longitudinal study using Duplex sonography

Blood viscosity and haemostatic factors in late pregnancy, pre‐eclampsia and fetal growth retardation

Adaptation of lung, chest wall, and respiratory muscles during pregnancy: preparing for birth

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