Maternal Cardiovascular Impairment in Pregnancies Complicated by Severe Fetal Growth Restriction

Relevance of Haemodynamics in Treating Pre-eclampsia

Blood pressure is a way of describing the end result of changes in cardiac output, intravascular volume and peripheral resistance. It has certain advantages in that it is a reproducible and easily measured parameter, but in itself, it offers only a limited understanding of the underlying haemodynamics. In pregnancy, profound haemodynamic changes occur and in hypertensive diseases of pregnancy defining a condition by blood pressure alone risks missing the underlying cause. Partly, this has been a problem of ascribing the cause of hypertensive syndromes to the placenta which has inhibited rigorous research into other possible causes of haemodynamic dysfunction. It is becoming increasingly evident that hypertension in pregnancy may be associated with primarily high cardiac output or high peripheral resistance. A knowledge of the underlying type of hypertension may allow more rational treatment of these conditions in pregnancy rather than therapeutic attempts at controlling blood pressure by any means possible as an end in itself.

Echocardiographic Techniques of Deformation Imaging in the Evaluation of Maternal Cardiovascular System in Patients with Complicated Pregnancies

Cardiovascular diseases (CVD) represent the leading cause of maternal mortality and morbidity. Knowledge of CVD in women is constantly evolving and data are emerging that female-specific risk factors as complications of pregnancy are conditions associated with an increased risk for the long-term development of CVD. Echocardiography is a safe and effective imaging technique indicated in symptomatic or asymptomatic pregnant women with congenital heart diseases who require close monitoring of cardiac function. Deformation imaging is an echocardiographic technique used to assess myocardial function by measuring the actual deformation of the myocardium through the cardiac cycle. Speckle-tracking echocardiography (STE) is a two-dimensional (2D) technique which has been found to be more accurate than tissue Doppler to assess both left ventricular (LV) and right ventricular (RV) myocardial function. The use of 2D STE however might present some technical issues due to the tomographic nature of the technique and the motion in the three-dimensional space of the myocardial speckles. This has promoted the use of 3D STE to track the motion of the speckles in the 3D space. This review will focus on the clinical value of the new echocardiographic techniques of deformation imaging used to assess the maternal cardiovascular system in complicated pregnancies.

Longitudinal maternal hemodynamics in pregnancies affected by fetal growth restriction

OBJECTIVE

Fetal growth restriction (FGR) is a powerful determinant of poor perinatal outcome. From our previous work in pregnancies at high risk of development of hypertension we found impaired cardiovascular adaptation early in gestation in those destined to deliver growth-restricted infants. In this study, we monitored serially maternal hemodynamics from the first to third trimester in a similar high-risk cohort, in order to determine whether this distinct hemodynamic profile found at presentation persisted throughout pregnancy in those complicated by FGR.

METHODS

This was a prospective observational study based at a specialist antenatal hypertension clinic at a tertiary hospital in London. Maternal hemodynamics were evaluated serially using a non-invasive bioreactance method in pregnant women referred to the clinic with a history of chronic hypertension or a history of hypertensive disorder in a previous pregnancy. Differences in maternal hemodynamic parameters were compared between women who delivered a baby with a birth weight ≥ 10^th vs < 10^th percentile and ≥ 5^th vs < 5^th percentile.

RESULTS

Eighty-four pregnant women were included in the study. Mean gestational age at presentation was 14.3 weeks. Sixteen women delivered babies with a birth weight < 10^th percentile and 11 with a birth weight < 5^th percentile. In pregnancies with a birth weight ≥ 10^th percentile, longitudinal maternal hemodynamics showed a pattern consistent with well-established physiological changes in pregnancy, i.e. a reduction in vascular resistance and an increase in cardiac output with advancing gestation until mid-pregnancy. However, women who delivered babies with a birth weight < 10^th percentile showed a static pattern with no change during gestation and lower cardiac output and higher peripheral vascular resistance. Similar differences were seen when the 5^th percentile was used to discriminate between appropriately-grown and growth-restricted babies.

CONCLUSION

Serial assessment of maternal hemodynamics in high-risk women identifies distinctive trends associated with pregnancies destined to deliver babies with birth weights < 10^th and < 5^th percentiles. These pregnancies have a suppressed and static maternal cardiac output and stroke volume, and have consistently raised peripheral vascular resistance. This suggests that, in women with chronic hypertension or a history of hypertensive disorder in a previous pregnancy, FGR is associated with a primary and persistent failure of maternal cardiovascular adaptation in pregnancy. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Change in maternal cardiac output from preconception to mid-pregnancy is associated with birth weight in healthy pregnancies

OBJECTIVE

Birth weight (BW) is thought to be determined by maternal health and genetic, nutritional and placental factors, the latter being influenced by anatomical development and perfusion. Maternal cardiovascular changes contribute to uteroplacental perfusion; however, they have not yet been investigated in relation to fetal growth or BW. Our aim was to explore the relationship between maternal cardiovascular adaptation, fetal growth and BW in healthy pregnancies.

METHODS

This was a longitudinal prospective study of women planning to conceive a pregnancy. Maternal cardiac output (CO), cardiac index (CI), pulse-wave velocity, aortic augmentation index, central blood pressure and peripheral vascular resistance were assessed prior to pregnancy and at 6, 23 and 33 weeks' gestation. Fetal growth was assessed using serial ultrasound measurements of biometry.

RESULTS

In total, 143 women volunteered to participate and were eligible for study inclusion. A total of 101 women conceived within 18 months and there were 64 live births with normal pregnancy outcome. There were positive correlations between BW and the pregnancy-induced changes in CO (ρ = 0.4, P = 0.004), CI (ρ = 0.3, P = 0.02) and peripheral vascular resistance (ρ = 0.3, P = 0.02). There were significant associations between second-to-third-trimester fetal weight gain and the prepregnancy-to-second-trimester increase in CO (Δ, 0.8 ± 1.2 L/min; ρ = 0.3, P = 0.02) and CI (Δ, 0.4 ± 0.6 L/min/m² ; ρ = 0.3, P = 0.04) and reduction in aortic augmentation index (Δ, -10 ± 9%; ρ = -0.3, P = 0.04).

CONCLUSIONS

In healthy pregnancy, incremental changes in maternal CO in early pregnancy are associated with third-trimester fetal growth and BW. It is plausible that this association is causative as the changes predate third-trimester fetal growth and eventual BW. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Prehypertension in Pregnancy and Risks of Small for Gestational Age Infant and Stillbirth

It is not fully known whether maternal prehypertension is associated with increased risk of adverse fetal outcomes, and it is debated whether increases in blood pressure during pregnancy influence adverse fetal outcomes. We performed a population-based cohort study in nonhypertensive women with term (≥37 weeks) singleton births (n=157 446). Using normotensive (diastolic blood pressure [DBP] <80 mm Hg) women as reference, we calculated adjusted odds ratios with 95% confidence intervals between prehypertension (DBP 80–89 mm Hg) at 36 gestational weeks (late pregnancy) and risks of a small-for-gestational-age (SGA) birth or stillbirth. We further estimated whether an increase in DBP from early to late pregnancy affected these risks. We found that 11% of the study population had prehypertension in late pregnancy. Prehypertension was associated with increased risks of both SGA birth and stillbirth; adjusted odds ratios (95% confidence intervals) were 1.69 (1.51–1.90) and 1.70 (1.16–2.49), respectively. Risks of SGA birth in term pregnancy increased by 2.0% (95% confidence intervals 1.5–2.8) per each mm Hg rise in DBP from early to late pregnancy, whereas risk of stillbirth was not affected by rise in DBP during pregnancy. We conclude that prehypertension in late pregnancy is associated with increased risks of SGA birth and stillbirth. Risk of SGA birth was also affected by rise in DBT during pregnancy. Our findings provide new insight to the relationship between maternal blood pressure and fetal well-being and suggest that impaired maternal perfusion of the placenta contribute to SGA birth and stillbirth.

Apelin in Normal Pregnancy and Pregnancies Complicated by Placental Insufficiency

INTRODUCTION

Apelin is a potent inotropic agent and causes endothelium-mediated vasodilation. Its cardiovascular profile suggests a role in the regulation of gestational hemodynamics.

METHODS

We longitudinally assessed maternal serum apelin levels and hemodynamics (cardiac output and total peripheral resistance) between 20 and 34 weeks gestation in 18 women at high risk of placental dysfunction. Placental apelin staining was assessed by immunohistochemistry in placentas from uncomplicated pregnancies (n = 6), preterm deliveries (n = 6), preeclampsia (PET, n = 8), and isolated intrauterine growth restriction (IUGR, n = 8). Placental apelin gene expression was assessed by quantitative polymerase chain reaction.

RESULTS

In the high-risk cohort, 4 fetuses developed isolated IUGR and 6 women developed PET. We obtained a median of 5 (range 2-9) hemodynamic and apelin measurements per woman. Apelin levels throughout gestation were best fitted by a quadratic curve. Apelin levels between 20 and 26 weeks gestation correlated with total peripheral resistance (r = .57, P = .01) and showed a trend toward an inverse correlation with stroke volume (r = -.42, P = .08). Apelin serum levels were 30% lower in pregnancies complicated by IUGR than in uncomplicated pregnancies or in women with preeclampsia (P = .009). Placental apelin gene expression was similar in IUGR, PET, preterm, and term normal placentas. Apelin staining was seen both in syncytiotrophoblast and stroma of the placental villi. In IUGR placentas, apelin staining was strongly decreased in both compartments compared to normals. Preeclamptic placentas showed an intermediate staining.

CONCLUSIONS

Apelin levels mirror the cardiovascular changes seen in pregnancy. Serum and placental apelin levels are decreased in IUGR.

Endothelial cell dysfunction and cardiac hypertrophy in the STOX1 model of preeclampsia

Preeclampsia is a disease of pregnancy involving systemic endothelial dysfunction. However, cardiovascular consequences of preeclampsia are difficult to analyze in humans. The objective of the present study is to evaluate the cardiovascular dysfunction induced by preeclampsia by examining the endothelium of mice suffering of severe preeclampsia induced by STOX1 overexpression. Using Next Generation Sequencing on endothelial cells of mice carrying either transgenic or control embryos, we discovered significant alterations of gene networks involved in inflammation, cell cycle, and cardiac hypertrophy. In addition, the heart of the preeclamptic mice revealed cardiac hypertrophy associated with histological anomalies. Bioinformatics comparison of the networks of modified genes in the endothelial cells of the preeclamptic mice and HUVECs exposed to plasma from preeclamptic women identified striking similarities. The cardiovascular alterations in the pregnant mice are comparable to those endured by the cardiovascular system of preeclamptic women. The STOX1 mice could help to better understand the endothelial dysfunction in the context of preeclampsia, and guide the search for efficient therapies able to protect the maternal endothelium during the disease and its aftermath.

Maternal subclinical vascular changes in fetal growth restriction with and without pre-eclampsia

OBJECTIVE

To assess maternal vascular structure and function in pregnancies complicated by fetal growth restriction (FGR), in women with and without pre-eclampsia (PE) at the time of FGR diagnosis.

METHODS

We evaluated 124 women with a pregnancy complicated by FGR, of whom 60 had PE and 64 did not, and compared these findings to those of 110 normal women (controls). The group of FGR pregnancies without PE was further subdivided according to gestational age at FGR diagnosis into early onset (< 32 weeks) or late onset (≥ 32 weeks). Maternal carotid intima-media thickness (IMT), blood pressure (BP), carotid artery distensibility (CD), circumferential wall stress (CWS) and inferior vena cava (IVC) collapsibility were assessed by ultrasound at the time of FGR diagnosis.

RESULTS

Compared to controls, cases of FGR with PE showed increased maternal carotid IMT (0.425 (interquartile range (IQR), 0.381-0.486) vs 0.409 (IQR, 0.386-0.439) mm; P = 0.021), BP (mean, 109 (IQR, 101-117) vs 82  (IQR, 77-89) mmHg; P  < 0.001) and CWS (19.7 (IQR, 17.0-22.7) vs 12.2 (IQR, 11.1-13.7) kPa; P < 0.001), and reduced CD (25.3 (IQR, 15.7-35.6) vs 31.9 (IQR, 25.4-41.1) kPa(-1)  × 10(-3) ; P = 0.037) and IVC collapsibility indices (0.07 (IQR, 0.06-1.11) vs 0.10 (IQR, 0.06-0.13); P  =  0.136). Similarly, compared to controls, in cases of FGR without PE maternal carotid IMT (0.436  (IQR, 0.392-0.476) mm; P  = 0.001) and BP (88 (IQR, 81-95) mmHg; P < 0.001) were increased but CD and IVC collapsibility were similar. When analysis was subclassified according to gestational age at diagnosis, IMT and CWS were significantly increased only in early-onset FGR while BP was increased in both groups.

CONCLUSION

Normotensive women with pregnancy complicated by FGR share some subclinical vascular features with those of women with PE, which further reinforces the notion that, at least in a proportion of cases, there is a common placental disease that influences maternal cardiovascular features.

Maternal cardiac evaluation during uncomplicated twin pregnancy with emphasis on the diastolic function

OBJECTIVE

The objective of the study was to evaluate the longitudinal changes in maternal systolic and diastolic function in a series of women carrying an uncomplicated twin pregnancy.

STUDY DESIGN

A series of women carrying a twin pregnancy underwent standard M-mode, 2-dimensional color Doppler, and tissue Doppler transthoracic echocardiography during the first (11-13 weeks), the second (20-23 weeks), the third (28-32 weeks) trimesters, and the postpartum (6 months after delivery).

RESULTS

From January 2012 to September 2013, 30 women with an uncomplicated twin pregnancy were included in this prospective study. All the pregnancies were diamniotic including 24 dichorionic and 6 monochorionic sets. Overall, 60 live births were observed with a mean gestational age at delivery of 37 ± 1 weeks and a mean birthweight of 2532 ± 313 g. During pregnancy a significant worsening of left ventricle systolic function expressed by ejection fraction, fractional shortening and S1 longitudinal contractility decrease was observed. These findings also persisted at postpartum assessment. Regarding diastolic function, our data showed a significant progressive reduction of pulsed Doppler E-wave velocity and an increase of A-wave from the first to the third trimester. Similar changes were documented for tissue Doppler E1 and A1 peak velocities assessed at the level of the mitral and tricuspid annulus. After delivery diastolic findings returned to values comparable with those obtained in the first trimester.

CONCLUSION

In uncomplicated twin gestations, significant changes in maternal systolic and diastolic function occur from the first to the third trimester. Moreover, although diastolic parameters normalize after pregnancy, a relative systolic dysfunction seems to persist after delivery.

The mother--the long-term implications on metabolic and cardiovascular complications

There is cumulating evidence linking the occurrence of pregnancy complications, including miscarriage, stillbirth, hypertensive disorders of pregnancy, gestational diabetes mellitus, preterm birth, and fetal growth restriction, with increased future risk of type 2 diabetes mellitus, and hospitalization and death due to cardiovascular and cerebrovascular diseases. Such association is largely related to genetic predisposition and shared pathophysiological mechanisms and changes, which may precede the index pregnancy. Awareness of this association would allow identification of the at-risk women for implementation of preventive measures to reduce the recurrence risk of these complications and mitigate the future development of metabolic and cardiovascular diseases worldwide.

Uterine artery Doppler, birth weight and timing of onset of pre-eclampsia: providing insights into the dual etiology of late-onset pre-eclampsia

OBJECTIVE

To investigate the relationship between uterine artery Doppler ultrasound indices and birth weight in women with early-, intermediate- and late-onset pre-eclampsia as compared with women with uneventful pregnancy outcome.

METHODS

In a retrospective, observational cohort study, uterine artery Doppler assessment was carried out at 18+0 to 23+6 weeks' gestation in 26,893 women attending for routine antenatal care in a tertiary care center. The mean resistance index (RI) and its relationship to the outcome of pregnancy and birth-weight centiles were evaluated.

RESULTS

Uterine artery RI showed a significant, negative correlation with birth weight (r= -0.20, P<0.0001). Patients with early-onset pre-eclampsia had an increased prevalence of high uterine artery mean RI, above the 90(th) centile, corresponding to an increased proportion of small-for-gestational age (SGA) neonates with a birth weight below the 10(th) centile. In late-onset pre-eclampsia, however, there was an unexpectedly higher proportion of large-for-gestational-age (LGA) neonates with a birth weight above the 90(th) centile without a concurrent increase in the prevalence of low uterine artery mean RI below the 10(th) centile.

CONCLUSIONS

The finding of a bimodal skewed distribution of birth weight, with neonates exhibiting a higher prevalence of both LGA and SGA with late-onset pre-eclampsia, indicates that there are two types of late-onset pre-eclampsia. These findings explain the poor performance of mid-trimester uterine artery Doppler in predicting pre-eclampsia at term and provide insights into the placental origins of the early and late forms of pre-eclampsia.

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.

Cardiovascular disease in menopause: Does the obstetric history have any bearing?

Cardiovascular disease remains a leading cause of morbidity and mortality in menopausal women in spite of the overall reduction in age-adjusted mortality from the disease in the last few years. It is now clear that mechanisms of cardiovascular disease in menopausal women are similar to men and rather than midlife acceleration of cardiovascular disease in women, the final impact of cardiovascular disease in later life may be a reflection of cardiovascular changes during reproductive years as a result of woman’s obstetric history. A decade after the Women’s Health Initiative trial, there is upcoming evidence to suggest that hormone replacement therapy in young recently menopausal women has a cardioprotective effect. Cardiovascular changes during normal pregnancy or pregnancy complications such as preeclampsia may affect a woman’s long-term cardiovascular health. Therefore, it is plausible that the cardioprotective benefit of hormone replacement therapy depends on occult pre-existing cardiovascular risks in women in relation to their previous obstetric history. In this review, we describe the cardiovascular changes during and after pregnancy in obstetric complications such as recurrent miscarriage, preeclampsia, intrauterine growth restriction, preterm labour and gestational diabetes; existing evidence regarding their association with cardiovascular disease later in life, and hypothesize possible mechanisms. Our aim is to improve the understanding and highlight the importance of including obstetric history in risk assessment in menopausal women and individualizing their risks before prescribing hormone replacement therapy. Future research in risk benefit assessment of hormone replacement therapy should also account for a woman’s background cardiovascular risk in the light of her obstetric history.

Pregnancy Complications and Later Development of Hypertension

Pregnancy complications such as preeclampsia and diabetes affect approximately 5 to 10 % of all pregnancies and compromise maternal and fetal health during gestation. Complications during pregnancy may also contribute to the development of hypertension and future cardiovascular risk in the mother. Moreover, fetal exposure to hypertension and diabetes during pregnancy can program hypertension and cardiovascular disease in the offspring. Transgenerational transmission of programmed cardiovascular risk highlights the importance of understanding the mechanisms that link complications during pregnancy with later hypertension in her offspring and subsequent generations. However, experimental studies are needed to investigate the cause and effect of increased blood pressure in the mother following a complicated pregnancy and provide insight into the development of preventative measures that may improve the long-term cardiovascular health of women and their offspring.

Mid-gestational maternal cardiovascular profile in preterm and term pre-eclampsia: a prospective study

OBJECTIVE

Pre-eclampsia (PE) is associated with maternal cardiac remodelling and biventricular diastolic dysfunction. Preterm PE alone can also be associated with severe left ventricular hypertrophy and biventricular systolic dysfunction. The aim of this study was to assess whether the maternal cardiovascular profile at mid-gestation in nulliparous normotensive women differs in women destined to develop preterm PE versus those who will develop PE at term.

DESIGN

Prospective study.

SETTING

Tertiary referral university centre.

POPULATION

A total of 269 women, including 152 at increased risk of developing PE as determined by mid-gestational uterine artery Doppler assessment.

METHODS

Women underwent blood pressure profiling, echocardiography, cardiac tissue Doppler and strain rate analysis at 20-23 weeks of gestation.

MAIN OUTCOME MEASURES

Mid-gestational cardiovascular profile in women with normal pregnancy and those that subsequently developed preterm or term PE.

RESULTS

Pre-eclampsia subsequently developed in 46 women, including 18 with preterm PE. Women who subsequently developed PE, irrespective of gestation, had evidence of left ventricular concentric remodelling (33%) which was not found in the control women (P < 0.0001). Only women who developed preterm PE exhibited a high resistance-low volume haemodynamic state at mid-gestation. The latter group also had evidence of left ventricular diastolic or systolic dysfunction (33%) and segmental impaired myocardial relaxation (72%).

CONCLUSIONS

Asymptomatic cardiac diastolic dysfunction is evident at mid-gestation in women who subsequently develop preterm PE but not in those who develop term PE. These cardiac findings are useful in understanding the pathophysiology of PE and corroborate the concept that PE is not a single disorder, but a cluster of symptoms that have several different aetiologies.