Echocardiographic assessment of cardiovascular hemodynamics in normal pregnancy

OBJECTIVE: The factors affecting cardiac output in normal pregnancy remain controversial. This study prospectively evaluates maternal central hemodynamics and cardiac structure and function by echocardiography, together with maternal stature correction and correlation of these variables in healthy pregnant women in the latter half of pregnancy. METHODS: One hundred sixty echocardiographic studies were performed in 35 healthy pregnant women for longitudinal evaluation from early second trimester until term and 6-12 weeks postpartum. RESULTS: Cardiac output increased significantly at the early to mid third trimester and was maintained until term. It increased predominantly in the latter half of pregnancy, and peak cardiac output of 46-51% occurred from a 15% increase in heart rate and 24% increase in stroke volume. Maternal cardiac output measured in the early third trimester showed a good correlation with maternal body surface area (r = 0.72; P <.001) and fetal birth weight (r = 0.52; P =.008). Left ventricular systolic function was preserved until term. CONCLUSION: Maternal cardiac output peaks in the early to mid third trimester and is maintained until term. Significant correlations were observed among maternal cardiac output, maternal body surface area, and fetal birth weight.     

Factors influencing aortocaval compression in late pregnancy

The circulatory effects of postural change in late pregnancy were investigated in 20 healthy pregnant women. Maximum stroke volume (93.2 +/- 11.9 ml) was recorded with the subject in the left lateral position and was significantly (p less than 0.001) reduced in the supine, right lateral, and lithotomy positions, but was largely unchanged in the standing motionless position (89.9 +/- 12.6 ml). Diastolic, systolic, and mean arterial blood pressures and total peripheral vascular resistance were significantly (p less than 0.001) increased in the supine, right lateral, lithotomy, and upright motionless positions when compared to the same variables in the left lateral position. The following factors were found to be significantly correlated to the hemodynamic response to the supine recumbent position: maternal age (p less than 0.05), the position of the fetus in the uterus (p less than 0.05), and systolic (p less than 0.001) and diastolic (p less than 0.001) blood pressures measured with the subject in the left lateral position. The implications of the present findings for modern obstetric delivery care and the etiology of the supine hypotensive syndrome are discussed.     

Blood pressure and renal function during normal pregnancy

In order to obtain reference values during normal pregnancy 24 women with strict criteria for health and normal pregnancy were studied. Greatest interest was focused on blood pressure (BP) measurements and renal function tests. Investigations were made in early second trimester and in the 30th, 33rd and 36th gestational weeks. Gestational age was estimated by ultrasound measurement of crown-rump length before the 14th gestational week. Both systolic and diastolic BP measured in the right arm were about 10 mmHg lower in the left lateral position than when supine or standing. The difference is suggested to be dependent on hydrostatic factors. Diastolic BP should be defined at the fourth phase of the Korotkoff sounds in order to be reliable because of the common phenomenon of late or non-disappearance of the sounds during pregnancy. Diastolic BP in phase IV increased in up to 25% of the cases with 15 mmHg or more from early second trimester to the 36th gestational week in all three positions. Serum creatinine concentration was low in early second trimester and did not change during pregnancy, while serum urea decreased and serum urate increased during pregnancy. The results emphasize the importance of using reference values from a normal pregnant population obtained at different gestational weeks for comparison in studies on certain pathological conditions during pregnancy, especially pre-eclampsia.     

Effect of body position on PaO2 and PaCO2 during pregnancy

BACKGROUND: The body position may have an effect on gas exchange though the magnitude of this effect has not been studied thoroughly during the three trimesters of pregnancy. OBJECTIVES: This study analyzes the effect of body position change on arterial oxygen tension (PaO2) and arterial carbon dioxide tension (PaCO2) in healthy pregnant women. METHODS: We examined 21 lung healthy pregnant women at the end of the first, second and third trimester of pregnancy. Blood was drawn from the radial artery first in the sitting and subsequently in the supine position. Peak expiratory flow rate was determined as well. RESULTS: No statistically significant difference was detected between the mean values of PaO2 in the supine and in the sitting position at the end of the first trimester. On the contrary, at the end of the second trimester the mean value of PaO2 in the supine position was 92.39 +/- 1.95 mm Hg, while in the sitting position the mean PaO2 was 96.56 +/- 1.83 mm Hg (p < 0.001). At the end of the third trimester the mean PaO2 in the supine position was 90.48 +/- 2.91 mm Hg while in the sitting position the mean PaO2 was 97.48 +/- 1.46 mm Hg (p < 0.001). CONCLUSIONS: According to our data we conclude that the statistically significant difference in PaO2 in the sitting and supine positions clearly shows that the position needs to be considered both when attempting to establish reference values and when evaluating gas tensions at the end of pregnancy.     

Effect of maternal postural change on maternal hemodynamics in late pregnancy--supine hypertension

The purpose of this investigation was to ascertain the effect of postural change in late pregnant women from the left lateral recumbent position to the supine position on their blood circulation. Patients in whom the blood pressure at the right upper limb in the supine position increased by at least 20mmHg or more (diastolic and/or systolic pressure) were classified as the supine hypertensive group. Patients in whom the blood pressure of the right upper limb decreased by at least 20mmHg or more were classified as the supine hypotensive group. And other patients were classified as the no blood pressure change group. The results were as follows. 1. The incidence of supine hypertension was 48% in primigravidas and 38% in multigravidas. Supine hypertension was especially common in PIH (pregnancy induced hypertension) complicated women (75%). 2. Maternal cardiac function: With postural change from the left lateral recumbent position to the supine position, CO (cardiac output) decreased and SVR (systemic vascular resistance) was increased in both the supine hypertensive and the no blood pressure change groups by the thermodilution method (n = 14). CVP (central venous pressure) and PCWP (pulmonary capillary wedge pressure) shows different pattern of change in the supine hypertensive group and the no blood pressure change group. In the former group, CVP was decreased by 45 +/- 16% and PCWP was increased by 21 +/- 9% in the supine position compared with in the left lateral recumbent position. However, in the latter group, CVP decreased by 87 +/- 69% and PCWP decreased by 53 +/- 46% as the result of the same postural change.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardiovascular responses to the change from the left lateral to the upright position in pregnant hypertensives

Objective: To evaluate by non-invasive means, the autonomically mediated changes in heart rate and blood pressure in response to postural change in pregnancy. Method: Ninety-one patients were studied, of whom 17 were non-pregnant controls, 21 were normotensive parturients, 22 had non-proteinuric hypertension, and 31 were pre-eclamptics. In all patients the heart rate and blood pressure response to the change from the left lateral to the erect position was measured non-invasively, during the third trimester in the pregnant groups. Results: The change from the left lateral to the erect position induced significantly greater mean changes (increases) in systolic blood pressure in the normotensive pregnant (PC) women than all other groups (P<0.05). Pre-eclamptic patients (PE) exhibited significantly less of an increase in systolic blood pressure than the non-proteinuric hypertensive (H) group. Both the H and PC groups showed significantly greater increases in diastolic pressure than the non-pregnant (NP) group. PE patients had a significantly smaller increase in diastolic pressure than the H group. There were no significant differences between heart rate changes when comparing the PC, NP and H groups. The PE group exhibited a significantly greater increase in heart rate on adopting the erect position than all other groups. Conclusions: Pre-eclamptics exhibit smaller changes in blood pressure than normotensive pregnant patients and non-proteinuric hypertensives on standing, while producing an exaggerated heart rate response, indicating altered autonomic compensatory mechanisms in these patients.     

Maternal cardiovascular adaptations to twin pregnancy

Multiple pregnancy places increased demands on the maternal circulation. Maternal left ventricular size and performance were measured with M-mode echocardiography in women with twin pregnancy in the second and third trimesters, and the findings were compared to those in normal singleton pregnancies. As expected, cardiac output was greater during twin than during singleton pregnancy; however, end-diastolic ventricular dimension was not. Output was increased in twin pregnancy during the second and third trimesters by heart rate and also during the third trimester by stroke volume. Increased stroke volume was effected by increased shortening, thus strongly suggesting increased contractility. Increased maternal heart rate and contractility during multiple gestations suggest that cardiovascular reserve is reduced.     

Left ventricular diastolic filling response to stationary bicycle exercise during pregnancy and the postpartum period

OBJECTIVE: The purpose of this study was to determine the effects of pregnancy and of maximal exercise on left ventricular diastolic filling response. STUDY DESIGN: Transmitral pulsed Doppler echocardiography was obtained in 10 healthy women during each trimester of pregnancy and at 12 weeks after delivery. Doppler studies were performed at rest and at each exercise workload. The P-R interval, the early and atrial peak flow velocities, the mitral early deceleration time, and the isovolumetric relaxation time were analyzed. Data are expressed as the mean and standard deviation of the mean. Values obtained during the last trimester of pregnancy were used as the pregnant value; values at the 12 weeks after delivery were used as the nonpregnant value. Paired t -test, analysis of variance, and mixed models were used to determine significance with a probability value of <.05. RESULTS: Pregnancy significantly increased the early and atrial peak flow velocities. Pregnancy decreased the P-R interval, the early deceleration time, and the isovolumetric relaxation time. Exercise significantly decreased these diastolic functions; but pregnancy, in any of the 3 trimesters, did not significantly affect this response. CONCLUSION: Pregnancy increased left ventricular diastolic camber stiffness at rest and shifted left ventricular diastolic filling during exercise from predominantly early to atrial filling. This finding suggests that there is an increase in left ventricular chamber stiffness during maximal upright bicycle exercise in pregnancy.     

Effect of orthostatic stress on umbilical Doppler waveforms in normal and hypertensive pregnancies.

OBJECTIVE: Our study examined the effects of orthostatic stress and maternal hemodynamics on umbilical systolic/diastolic ratios in normal and hypertensive pregnancies. STUDY DESIGN: Eighteen normal and 20 hypertensive third-trimester pregnancies were examined in the left lateral recumbent, sitting, and standing positions. Measurements included umbilical systolic/diastolic ratio, maternal blood pressure, maternal cardiac output, and maternal total peripheral resistance. RESULTS: All patients demonstrated a fall in cardiac output and a rise in total peripheral resistance with standing. No change in systolic/diastolic ratio occurred with change to the upright position in patients with normotension. Patients with hypertension exhibited a significant increase in umbilical systolic/diastolic ratio with postural change. The increase was more marked in women who had hypertension with elevated peripheral resistance. CONCLUSION: Patients with hypertension are at increased risk of elevation of systolic/diastolic ratio with postural change; women with high-resistance hypertension may be at highest risk.     

Effects of fish oil supplementation in late pregnancy on blood pressure: a randomised controlled trial

Objective To study the effect of fish oil supplementation on blood pressure during the third trimester of pregnancy.
Design In the 30th week of pregnancy 533 healthy women were randomly assigned in a ratio 2:1:1 to receive fish oil (2–7 g/day n-3 fatty acids (Pikasol)), or a control regimen of either olive oil or no oil supplementation.
Main Outcome measures Blood pressure measured with an automatic device (Dinamap 1846 SX, Criticon) at baseline and in weeks 33, 37, 39 and subsequently weekly until delivery.
Results Mean blood pressure increased during the third trimester, and this was not influenced by group assignment. No significant effects on either systolic or diastolic blood pressure were seen in the fish oil group compared to the control groups. The proportions of women with a systolic blood pressure above 140 mmHg or a diastolic blood pressure above 90 mmHg were not significantly different in the fish oil group compared with the control groups, although the proportion of women with diastolic above 90 mmHg tended to be lower in the fish oil group compared with the olive oil group. The corresponding relative risk was RR = 048 (95 % CI 0.22–1.06;   P = 007  ).
Conclusion 2.7 g/day of marine n-3 fatty acids provided in the third trimester of normal pregnancy showed no effect on blood pressure.     

The reasons for termination of pregnancy in the third trimester

Objective To analyse the process in making decisions leading to termination of pregnancy in the third trimester and to evaluate the maternal morbidity associated with this procedure.
Design Retrospective study.
Setting The Maternité Port Royal University Hospital, Paris, France.
Population A consecutive series of 956 terminations of pregnancy performed for fetal anomalies in singleton pregnancies, 305 of which were in the third trimester and 651 in the second.
Main outcome measures Indications for termination of pregnancy; process leading to late termination of pregnancy; maternal morbidity.
Results One hundred and thirteen (37%) third trimester terminations of pregnancy were associated with false negative resulted from the results of earlier screening tests. In 15 terminations (15%), the decision was postponed, although the poor fetal prognosis was established earlier. In 55 (18%) the diagnosis was not possible earlier than the third trimester, and in 122 (40%) the diagnosis was possible earlier but the poor prognosis for the fetus was not established until the third trimester. Maternal morbidity due to termination of pregnancy was similar in the second and third trimester.
Conclusion One-third of late terminations of pregnancy could have been avoided by more efficient screening in the second trimester. However, because fetal prognosis is not always clear when a malformation is diagnosed, postponing the decision until fetal development allows more thorough evaluation and may avoid unnecessary termination of pregnancy in the second trimester. This could be the main beneficial aspect of not setting a limit to the gestational age for performing termination of pregnancy. To analyse the process in making decisions leading to termination of pregnancy in the third trimester and to evaluate the maternal morbidity associated with this procedure. The Maternit6 Port Royal University Hospital, Paris, France.     

Effects of supine exercise on fetal heart rate in the second and third trimesters

The effects of a brief period of supine exercise on fetal heart rate (FHR) was studied in 25 healthy, regularly exercising women, 12 in the late second trimester and 13 in the mid third trimester. Although statistically significant increases in maternal mean arterial pressure and pulse occurred, the exercise intensity was mild, with the average percent maximal pulse being 46 +/- 5% and 49 +/- 5% in the second and third trimester groups, respectively. Small increases in FHR were seen in both groups, which were insignificant statistically and physiologically. No patient experienced significant FHR abnormalities as a result of the supine exercise sequence. The findings suggest that pregnant women may continue submaximal supine exercise of short duration into the mid to late third trimester.     

An ultrasound study of gestational and postural changes in the deep venous system of the leg in pregnancy

Objective To investigate gestational and postural changes in diameter and blood flow in the proximal deep leg veins during pregnancy.
Design A longitudinal, prospective observational study.
Setting The ultrasound department of a teaching maternity hospital.
Population Twenty-four healthy women with uncomplicated singleton pregnancies.
Methods Real-time and duplex Doppler ultrasound assessments of the vessel diameter, flow velocity and respiratory flow fluctuation in the proximal deep leg veins of women serially measured from the first trimester of pregnancy to six weeks postnatally.
Main outcome measures The effects of increasing gestation and the adoption of the left lateral position on the above parameters.
Results An increase in vessel diameter and a fall in flow velocity with increasing gestation was observed. However, no change in venous flow variation was observed. Delivery had reverse effects. Flow velocity was slower in the left than the right legs, but on adoption of the left lateral position an increase in flow velocity and venous flow variation was observed in both legs during pregnancy.
Conclusions These data are consistent with the observed increase in incidence and pattern of deep venous thrombosis in pregnancy and may aid interpretation of duplex Doppler ultrasound examinations for deep venous thrombosis in pregnancy. Postural changes should be part of this evaluation. The gravid uterus may not be the sole cause for postural changes in deep venous flow velocity.     

Serial noninvasive evaluation of cardiovascular hemodynamics during pregnancy

M-mode echocardiography, in combination with electrocardiography and phonocardiography, has been used to measure pulmonary capillary pressure as well as other cardiac functions. Serial hemodynamic evaluations by use of this technique were performed in seven healthy pregnant women in the recumbent position. Each patient had five studies: four antenatal studies and one postpartum study that served as a control. Mean pulmonary capillary pressure was within normal limits throughout pregnancy and the puerperium. Cardiac output did not increase significantly by the end of the first or second trimester but became elevated by 31% in the early third trimester. This elevation in cardiac output persisted until delivery and resulted from a comparable increase in heart rate. Stroke volume and ejection fraction did not change significantly, while peripheral vascular resistance fell, although not significantly, reaching a nadir at approximately 28 weeks of gestation. Our findings indicate that maternal cardiac output increases due to an increased heart rate and reduced afterload.     

Maternal cerebral hemodynamics in the supine hypotensive syndrome.

Cerebral hemodynamics were studied in eight nonpregnant women and 24 women in late pregnancy by internal carotid artery velocimetry with a 3.5-MHz continuous-wave Doppler system. Criteria for supine hypotensive syndrome were a mean blood pressure decrease of 15 mmHg and a 2-minute sustained increase in pulse of 20 beats per minute under postural change from the left lateral to supine position. Nonpregnant and normal pregnant controls not meeting these two criteria displayed decreases of 22.9 and 21.7%, respectively, in time-averaged mean peak velocity (mean velocity) in the supine position compared with the left lateral position. Five subjects with subclinical supine hypotensive syndrome who met one of the above criteria showed a 37.0% decrease in internal carotid artery mean velocity in the supine position. Two patients with supine hypotensive syndrome could not tolerate the supine position for more than 6 minutes, at which time internal carotid artery mean velocity fell below 10 cm/second, reverse flow was observed, and they complained of dizziness, nausea, and syncope. Internal carotid artery mean velocity in all women showed no change in the sitting position compared with the left lateral position. These results indicate that the supine position should be avoided in late pregnancy, especially by women with cerebrovascular complications.     

Hemodynamic Adaptation during Pregnancy in Chronic Hypertension

Objective: To assess hemodynamic and NT-proANP changes in women with chronic hypertension during pregnancy. Methods: Stroke volume index (SI), heart rate (HR), cardiac output index (CI), systemic vascular resistance index (SVRI), pulse wave velocity (PWV), and left cardiac work index (LCWI) were measured using whole-body impedance cardiography. Systolic blood pressure (SAP), mean arterial pressure (MAP), diastolic blood pressure (DAP), and pulse pressure (PP) were also measured. Arterial compliance was defined as the SI-to-PP ratio (SI/PP). Hemodynamic parameters and NT-proANP concentrations were assessed during the early and late second trimester, the third trimester, and after delivery in 20 women with essential hypertension and 30 normotensive women. Results: Arterial blood pressure, SVRI, and PWV remained higher during the whole study period in chronic hypertensive compared with healthy pregnancies. In the early second trimester, women with chronic hypertension had significantly lower SI and NT-proANP concentrations than did normotensive women. Conclusion: The hemodynamics of chronic hypertension during pregnancy are characterized by persistent high vascular resistance. Lower SI and NT-proANP values found in chronic hypertensive pregnancies during the early second trimester may suggest a reduced intravascular volume increase during pregnancy.     

Blood pressure and heartfrequency changes in pregnancy – Value of hypertonia

Summary The mean arterial blood pressure is decreased during the first two trimesters of pregnancy and increases to preconceptional values during the last weeks of gestation. The heart rate increases during the whole course of pregnancy. During late gestation fewer patients show an increase in diastolic blood pressure and heart rate in the standing position. A fall in heart rate was only seen in this period. A fall in mean arterial blood pressure during standing is not related to the blood pressure in the supine position during the whole course of pregnancy. The hypotensive symptoms are twice as frequent during early pregnancy compared to late pregnancy. Headaches, fatigue and cold extremities are the most usual complaints. The frequency and intensity of these three symptoms decrease during gestation. Blood pressure in the supine position is reduced in symptomatic pregnant women. However, the occurrence of these symptoms is not correlated to the fall in blood pressure in the standing position. The Birth-weight is not influenced by blood pressure in the supine position, but depends on the fall in blood pressure during standing. Pregnant women with a more pronounced fall in blood pressure give birth to newborns with a lower birthweight. These results imply a hitherto unknown cause of intrauterine growth restriction.      

Inferior vena cava diameter and the risk of pregnancy-induced hypertension and fetal compromise.

OBJECTIVE: Our objective was to investigate a possible clinical usefulness of the measurement of the inferior vena caval diameter (IVCD) during the late second trimester in predicting obstetrical complications. METHODS: IVCD was measured in the supine and complete left lateral positions in 281 pregnant women at 24-27 weeks' gestation. RESULTS: In 35 cases who showed the IVCD < or = 10 percentile in the complete left lateral position, there were six cases with pregnancy-induced hypertension and seven cases with a compromized fetus (with fetal distress and/or an Apgar score < 7 at 1 min), each incidence being significantly higher compared with cases with IVCD > 10 percentile. CONCLUSION: The measurement of IVCD in the complete left lateral position may provide a valuable tool in predicting pregnancy outcome given its non-invasiveness and easiness.     

Hemodynamic changes during twin pregnancy. A Doppler and M-mode echocardiographic study

Serial hemodynamic investigations were performed in 10 women with twin pregnancies at 20, 24, 28, 32, and 36 weeks' gestation and at 6 months after delivery. Cardiac output was measured by Doppler and cross-sectional echocardiography at the aortic, pulmonary, and mitral valves. Cardiac chamber size and ventricular function were investigated by M-mode echocardiography. The hemodynamic results were compared with those of 13 women with singleton pregnancies. Mean Doppler cardiac output was increased at 20 weeks of twin pregnancy (7.63 L/min) and showed no significant change during the remainder of pregnancy, but fell to 5.07 L/min after delivery. This increase was significantly greater than that recorded during singleton pregnancy, because of a relatively greater increase in heart rate. Twin pregnancy was associated with a significantly greater increase in left atrial dimension, but the increases in left ventricular dimensions, wall thickness, and function were comparable to those recorded in singleton pregnancy.