Maternal arterial stiffness in normotensive pregnant women who subsequently deliver babies that are small for gestational age

Preconception blood pressure and risk of gestational hypertension and preeclampsia: a large cohort study in China

Our objective was to examine whether high blood pressure in the preconception period was associated with gestational hypertension and preeclampsia in Chinese women. Data were obtained from the China-US Collaborative Project for Neural Tube Defects Prevention, a large population-based cohort study. We included 45,628 women who were registered before pregnancy in seven counties in South China. Blood pressure was measured during registration by trained health care workers, and other health-related information was recorded prospectively. We used logistic regression to evaluate the associations between preconception blood pressure and the risk of gestational hypertension and preeclampsia, adjusting for potential confounders. The prevalence of hypertension in the preconception study population was 4.57% (2083/45,628). The incidences of gestational hypertension and preeclampsia were 11.95% and 4.08%, respectively, in the hypertension group and 8.60% and 2.28%, respectively, in the nonhypertension group. Compared with the nonhypertension group, the hypertension group showed a significantly increased risk for gestational hypertension [adjusted risk ratio (RR) = 1.40, 95% confidence interval (CI): 1.22-1.60] and preeclampsia [adjusted RR = 1.75, 95% CI: 1.39-2.19]. When participants with normal blood pressure were used as the reference, the adjusted ORs for gestational hypertension were 1.48 (95% CI: 1.37-1.59), 1.70 (95% CI: 1.44-2.01), and 1.29 (95% CI: 1.02-1.64), and for preeclampsia, the adjusted ORs were 1.55 (95% CI: 1.35-1.78), 1.95 (95% CI: 1.46-2.60), and 1.99 (95% CI: 1.39-2.85) for the participants with prehypertension, stage 1 hypertension, and stage 2 hypertension, respectively. Our results support an association between hypertension or higher blood pressure prior to pregnancy and an increased risk of gestational hypertension and preeclampsia.

Preeclampsia: Maternal Systemic Vascular Disorder Caused by Generalized Endothelial Dysfunction Due to Placental Antiangiogenic Factors

Preeclampsia, a systemic vascular disorder characterized by new-onset hypertension and proteinuria after 20 weeks of gestation, is the leading cause of maternal and perinatal morbidity and mortality. Maternal endothelial dysfunction caused by placental factors has long been accepted with respect to the pathophysiology of preeclampsia. Over the past decade, increased production of placental antiangiogenic factors has been identified as a placental factor leading to maternal endothelial dysfunction and systemic vascular dysfunction. This review summarizes the recent advances in understanding the molecular mechanisms of endothelial dysfunction caused by placental antiangiogenic factors, and the novel clinical strategies based on these discoveries.

Longitudinal study to assess changes in arterial stiffness and cardiac output parameters among low-risk pregnant women

AIM

A single-centre, prospective longitudinal study to assess changes in maternal arterial stiffness and cardiac output parameters among low-risk healthy pregnant women.

METHODOLOGY

Thirty low-risk, healthy, pregnant women attending their routine antenatal dating ultrasound scan were recruited. Non-invasive assessment of arterial stiffness and cardiac output was undertaken at five gestational windows from 11 to 40 weeks of pregnancy. Data were analysed using a linear mixed model incorporating time and other relevant predictors as fixed effects, and patient as a random effect.

RESULTS

Gestational age had a significant effect on all arterial stiffness parameters, including brachial augmentation index (AIx) (p = .001), aortic AIx (p = .002) and aortic pulse wave velocity (p = .002). The aortic AIx (%) reduced during pregnancy: the lowest mean (standard error, SE) was 4.07 (1.01) at 28 weeks before it increased to 7.04 (SE 1.64) at 40 weeks. Similarly, non-invasive assessments of cardiac output (p < .001), stroke volume (p = .014), heart rate (p < .001) and total peripheral resistance (p < .001) demonstrated significant changes with gestational age. Mean cardiac output (l/m) increased during pregnancy reaching a peak at 28 weeks gestation 6.66 (SE 0.28), but dropped thereafter to reach 5.71 (SE 0.25) around term.

CONCLUSION

The current study provides pregnancy normograms for gestational changes in arterial stiffness and cardiac output parameters among low-risk, healthy pregnant women. Further work will be required to assess the risk of placental mediated diseases and pregnancy outcome among pregnant women with parameters outside the normal range.

Longitudinal study of vascular structure and function during normal pregnancy

OBJECTIVE

To examine alterations in maternal vascular structure and function during normal pregnancy.

METHODS

We assessed brachial and central blood pressure, pulse-wave velocity and augmentation index (by pulse-wave analysis and applanation tonometry), common carotid artery structure (by ultrasonography) and endothelial function in the brachial artery (by postischemic hyperemia-induced flow-mediated vasodilatation by glyceryl trinitrate) and in the forearm skin microcirculation (by laser Doppler perfusion imaging during iontophoretic administration of acetylcholine and sodium nitroprusside) in 52 healthy nulliparous women at 14, 24 and 34 weeks' gestation, and at 9 months postpartum.

RESULTS

During pregnancy, brachial and central systolic and diastolic blood pressures initially decreased but subsequently increased (all P < 0.05). Flow-mediated vasodilatation in the brachial artery increased during early pregnancy (P < 0.05), whereas non-specific vasodilatation by glyceryl trinitrate decreased (P < 0.01), indicating improved endothelial function. Thus, endothelial function index (forearm blood flow/glyceryl trinitrate) increased during pregnancy (0.30 ± 0.18 in the non-pregnant state at 9 months postpartum and 0.51 ± 0.19, 0.61 ± 0.39 and 0.49 ± 0.30 in the first, second and third trimesters, respectively) (P < 0.001). Endothelium-dependent skin microvascular reactivity to acetylcholine also increased (P < 0.01). Carotid-femoral pulse-wave velocity decreased during pregnancy (5.88 ± 0.91 m/s in the non-pregnant state and 5.55 ± 0.67, 5.12 ± 0.66 and 5.62 ± 0.74 m/s in the first, second and third trimesters, respectively) (P < 0.001).

CONCLUSION

During normal pregnancy, the blood volume expansion necessary for sufficient fetal growth is accommodated by early and marked changes in the matvascular system. This seems to be dependent on normal adaptive endothelial and vascular function. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Pathophysiology of preeclampsia: an angiogenic imbalance and long-lasting systemic vascular dysfunction

Preeclampsia is a systemic vascular disorder characterized by new-onset hypertension and proteinuria after 20 weeks of gestation. This condition targets several organs, including the kidneys, liver and brain, and is the leading cause of maternal and perinatal morbidity and mortality. Furthermore, recent evidence has revealed preeclampsia as a significant risk factor for future cardiovascular diseases in these women. Over the past decade, increasing evidence has indicated that maternal angiogenic imbalances caused by placental antiangiogenic factors play a central role in the systemic vascular dysfunction underling preeclampsia. The severity of the maternal antiangiogenic state correlates closely with maternal and perinatal outcomes. Assessing angiogenic imbalance and several vascular function tests have also emerged as a way of detecting systemic vascular dysfunction during pregnancy. This review summarizes the current understanding of the pathophysiology of preeclampsia, its clinical applications and clinical evidence for future cardiovascular risks.

Preconception Blood Pressure and Risk of Low Birth Weight and Small for Gestational Age

Our objective was to examine whether high blood pressure in the preconception period was associated with low birth weight (LBW) and small-for-gestational age (SGA) in Chinese women. Data were obtained from the China–US Collaborative Project for Neural Tube Defects Prevention, a large population-based cohort study. We included 43 718 singleton live births delivered at gestational ages of 28−45 weeks to women who were registered before pregnancy in 7 counties in southern China. Blood pressure was measured during registration by trained healthcare workers, and other health-related information was recorded prospectively. We used logistic regression to evaluate the associations between preconception blood pressure and the risk of LBW and SGA, adjusting for potential confounders. The prevalence of hypertension in the preconception study population was 4.62% (2019/43 718). The incidences of LBW and SGA were 2.33% and 5.05% for the hypertension group and 2.01% and 5.68% for the nonhypertension group. Compared with the nonhypertension group, the hypertension group did not show significantly increased risk for LBW overall (adjusted risk ratio =1.16, 95% confidence interval 0.86−1.57) or SGA (adjusted risk ratio =0.89, 95% confidence interval 0.73−1.09). When participants with normal blood pressure were used as the reference, the adjusted risk ratio of SGA for prehypertensive women was 1.13 (95% confidence interval 1.03−1.25). Our results do not support an association between hypertension or higher blood pressure before pregnancy and increased risk of LBW or SGA.

Maternal Blood Pressure During Pregnancy and Early Childhood Blood Pressures in the Offspring: The GUSTO Birth Cohort Study

Although epidemiological studies suggest that offspring of women with preeclampsia are at increased risk to higher blood pressures and cardiovascular disease, little is known about the nature of blood pressures between the mother and her offspring. As blood pressures comprise of both pulsatile (systolic blood pressure [SBP] and pulse pressure [PP]) and stable (diastolic blood pressure [DBP]) components, and they differ between central and peripheral sites, we sought to examine maternal peripheral and central blood pressure components in relation to offspring early childhood blood pressures. A prospective birth cohort of 567 Chinese, Malay, and Indian mother-offspring with complete blood pressure information were studied. Maternal brachial artery SBP, DBP, and PP were measured at 26 to 28 weeks gestation; and central SBP and PP were estimated from radial artery waveforms. Offspring brachial artery SBP, DBP, and PP were measured at 3 years of age. Associations between continuous variables of maternal blood pressures (peripheral SBP, DBP, PP, central SBP, and PP) and offspring blood pressures (peripheral SBP, DBP, and PP) were examined using multiple linear regression with adjustment for maternal characteristics (age, education level, parity, smoking status, alcohol consumption and physical activity during pregnancy, and pre-pregnancy BMI) and offspring characteristics (sex, ethnicity, BMI, and height at 3 years of age). In the multivariate models, offspring peripheral SBP increased by 0.08 (95% confidence interval 0.00-0.17, P = 0.06) mmHg with every 1-mmHg increase in maternal central SBP, and offspring peripheral PP increased by 0.10 (0.01-0.18, P = 0.03) mmHg for every 1-mmHg increase in maternal central PP. The relations of maternal-offspring peripheral blood pressures (SBP, DBP, and PP) were positive but not statistically significant, and the corresponding values were 0.05 (-0.03 to 0.13; P = 0.21), 0.03 (-0.04 to 0.10; P = 0.35), and 0.05 (-0.02 to 0.13; P = 0.14), respectively. Maternal central pulsatile blood pressure components (SBP and PP) during pregnancy are associated with higher blood pressures in the offspring. This positive correlation is already evident at 3-years old. Studies are needed to further evaluate the effects of maternal central pulsatile blood pressure components during pregnancy and long-term cardiovascular health in the offspring.

The association between maternal blood pressures and offspring size at birth in Southeast Asian women

Background

Maternal blood pressures in pregnancy is an important determinant of offspring size at birth. However, the relationship between maternal blood pressures and offspring’s size at birth is not consistent and may vary between ethnic groups. We examined the relationship between maternal peripheral and central blood pressures and offspring size at birth in an Asian multi-ethnic cohort, and effect modifications by maternal ethnicity and obesity.

Methods

We used data from 713 participants in the Growing Up in Singapore Towards Healthy Outcomes study consisting of pregnant Chinese, Malay and Indian women recruited from two tertiary hospitals between 2009 to 2010. Peripheral systolic and diastolic blood pressures (SBP and DBP), and central SBP and pulse pressure (PP) were measured around 27 weeks of gestation. Biometric parameters at birth were collected from medical records.

Results

After adjusting for maternal and fetal covariates, each 1-SD increase (10.0 mmHg) in central SBP was inversely associated with birth weight (−40.52 g; 95% confidence interval (CI) -70.66 to −10.37), birth length (−0.19 cm; −0.36 to −0.03), head circumference (−0.12 cm; −0.23 to −0.02) and placental weight (−11.16 g; −20.85 to −1.47). A one-SD (11.1 mmHg) increase in peripheral SBP was also associated with lower birth weight (−35.56 g; −66.57 to −4.54). The inverse relations between other blood pressure measures and offspring size at birth were observed but not statistically significant. Higher peripheral SBP and DBP and central SBP were associated with increased odds of low birth weight (defined as weight <2500 g) and small for gestational age (defined as <10^th percentile for gestational age adjusted birth weight). Maternal adiposity modified these associations, with stronger inverse associations in normal weight women. No significant interactions were found with ethnicity.

Conclusions

Higher second-trimester peripheral and central systolic pressures were associated with smaller offspring size at birth, particularly in normal weight women. Findings from this study reinforces the clinical relevance of antenatal blood pressure monitoring.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-014-0403-1) contains supplementary material, which is available to authorized users.

Abnormal pressure-wave reflection in pregnant women with chronic hypertension: association with maternal and fetal outcomes

The current study tested the hypothesis that abnormal pressure-wave reflection may have an important role in identifying pregnant women with chronic hypertension who might develop pre-eclampsia (PE) and/or fetal growth restriction. Pulse-wave analyses were performed to assess maternal arterial stiffness during 26-32 weeks of gestation in 41 women with chronic hypertension. We measured the central systolic pressure (CSP) and augmentation index (AIx) noninvasively using pulse waveforms of the radial artery with an automated applanation tonometric system. In a multiple regression analysis that included AIx-75 (AIx at a heart rate of 75 beats per minute), brachial systolic pressure, maternal height, smoking status, gestational age at testing and the presence of antihypertensive treatment at testing as independent determinants, AIx-75 was the only significant determinant of birth weight, whereas the brachial systolic pressure was not. In pregnant women with chronic hypertension who subsequently developed both superimposed PE and fetal growth restriction, CSP, AIx, AIx-75, and the brachial systolic and pulse pressures were all significantly higher than those who did not develop superimposed PE nor small for gestational age. In contrast, AIx-75 was the only significantly elevated hemodynamic parameter in patients who developed fetal growth restriction but not superimposed PE. In addition, CSP was the only significantly elevated hemodynamic parameter in patients who developed superimposed PE but not fetal growth restriction. Abnormal pressure-wave reflection during 26-32 weeks of gestation showed a stronger correlation with birth weight than conventional brachial blood pressure. Our findings might provide new insight into the pathophysiology of fetal growth restriction as well as superimposed PE in pregnancies complicated with chronic hypertension.

Carotid calcification in mice: a new model to study the effects of arterial stiffness on the brain

BACKGROUND

Arterial stiffness has been identified as an important risk factor for cognitive decline. However, its effects on the brain's health are unknown, and there is no animal model available to study the precise impact of arterial stiffness on the brain. Therefore, the objective of the study was to develop and characterize a new model specific to arterial stiffness in order to study its effects on the brain.

METHODS AND RESULTS

Calcium chloride (CaCl2) was applied to carotid arteries of mice, inducing an increase in collagen distribution and intima-media thickness, a fragmentation of elastin, a decrease in arterial compliance and distensibility, and an increase in cerebral blood flow pulsatility (n=3 to 11). Calcium deposits were only present at the site of CaCl2 application, and there was no increase in systemic blood pressure or change in vessel radius making this model specific for arterial stiffness. The effects of carotid stiffness were then assessed in the brain. Carotid calcification induced an increase in the production of cerebral superoxide anion and neurodegeneration, detected with Fluoro-Jade B staining, in the hippocampus (n=3 to 5), a key region for memory and cognition.

CONCLUSIONS

A new model of arterial stiffness based on carotid calcification was developed and characterized. This new model meets all the characteristics of arterial stiffness, and its specificity allows the study of the effects of arterial stiffness on the brain.