Current topic: pre-eclampsia and the placenta

The role of serum markers and uterine artery Doppler in identifying at-risk pregnancies

Measures of placental dysfunction, including maternal serum analytes and Doppler studies, have been linked to adverse pregnancy outcomes, although the predictive ability of any single one is poor. Improved knowledge of the multifactorial nature of many of the adverse outcomes of pregnancy has sparked interest in the use of multi-parameter models that combine maternal serum analytes with measures of placental structure and blood flow. The combination of various first-trimester and second-trimester analytes and uterine artery Doppler screening show promise as potential screening tools, but large prospective studies are needed to further define their role in clinical practice.

Early left ventricular diastolic dysfunction in premature infants born to preeclamptic mothers

AIM

To evaluate the cardiac function in premature infants born to preeclamptic mothers and its clinical consequences.

METHODS

This was a prospective observational cohort study performed in a tertiary neonatal intensive care unit. Fifty-three premature infants born to preeclamptic mothers comprising the study group were evaluated and compared with 42 premature infants born to normotensive mothers (control group). Relationship between echocardiographic measures and neonatal morbidity were assessed as the main outcome measures.

RESULTS

Left ventricle end-diastolic dimension (LVEDD), peak flow velocities during early diastole (peak E wave), peak flow velocities during atrial contraction (peak A wave), and peak E/A ratio were significantly lower in the study group. Within the study group, these parameters were also significantly lower in infants with respiratory problems. LVEDD was significantly smaller in preeclamptic infants with intrauterine growth retardation (IUGR).

CONCLUSION

Left ventricle diastolic dysfunction (LVDD) was detected in premature infants born to preeclamptic mothers in the first week after delivery. LVDD was associated with higher incidence of respiratory problems, transient tachypnea of the newborn, longer duration of oxygen requirement, and IUGR.

Role of reactive oxygen species during hypertension in response to chronic antiangiogenic factor (sFlt-1) excess in pregnant rats

BACKGROUND

Preeclampsia is associated with increased levels of reactive oxygen species (ROS) and the antiangiogenic factor, soluble fms-like tyrosine kinase-1 (sFlt-1). Moreover, recent studies have indicated that chronic sFlt-1 excess causes hypertension in pregnant animals. The purpose of this study was to evaluate the role of ROS in mediating sFlt-1-induced hypertension in the pregnant rat.

METHODS

Mean arterial pressure (MAP), and plasma sFlt-1 and tissue ROS levels were measured in the following groups: (i) pregnant controls; (ii) sFlt-1-treated pregnant rats; (iii) Tempol-treated pregnant rats; (iv) sFlt-1- and Tempol-treated pregnant rats.

RESULTS

MAP increased from 104 ± 2 mm Hg in pregnant control rats to 118 ± 3 mm Hg (P = 0.002) in sFlt-1-infused rats. Basal and nicotinamide adenine dinucleotide phosphate (NADPH)-stimulated levels of tissue ROS were increased in response to excess sFlt-1 during pregnancy. Pretreatment with Tempol attenuated oxidative stress and hypertension in response to sFlt-1.

CONCLUSIONS

ROS play an important role in mediating hypertension in response to chronic sFlt-1 excess during pregnancy.

Pre-eclampsia: Definitions, paternal contributions and a four stage model

It is 40 years since I started researching pre-eclampsia. Much has changed but some old problems persist. These include the debate of how to define a syndrome, the inheritance and genetics of pre-eclampsia, why primiparae are so susceptible and is primipaternity important? If it is, in a multiparous pregnancy (after changing partners), the old hypothesis that pre-eclampsia is the outcome of failed maternal immunoregulation to accommodate nature's transplant - the fetus - must be confronted. These points are briefly reviewed and a four stage model of pre-eclampsia derived.

Morphological characteristics of placentas associated with idiopathic intrauterine growth retardation: a clinicopathologic study

OBJECTIVES

To investigate histopathologic findings, placental diameters and characteristics of syncytial knots in the placentas from idiopathic intrauterine growth retardation (IUGR) pregnancies, and to compare them with a normal birth weight group.

STUDY DESIGN

Based on strict eligibility criteria, this prospective case-control study included 52 term placentas from idiopathic IUGR pregnancies and 69 term placentas from normal birth weight pregnancies. The study was carried out at the Clinical Hospital Centre, Split, where all placentas were collected and examined. For each placenta, diameters were measured and the following histopathologic findings were recorded: infarction, intervillous thrombosis, abruption, villous branching and maturation, chorioamnionitis, decidual vasculopathy and hemorrhagic endovasculitis for each placenta. In addition we assessed quantitative (number of syncytial knots and number of syncytial nuclei per syncytial knot) and qualitative (density and surface area) characteristics of syncytial knots in each placental sample. Statistical significance was tested using chi(2)-test, Student's t-test and Mann-Whitney U-test. Statistical significance was set at P< or =0.05.

RESULTS

There was no difference in investigated histopathologic findings between idiopathic IUGR placentas and control group placentas. Placental diameters correlated significantly with neonatal birth weight (r=0.64; P<0.01); with higher birth weight there is an increase in placental diameters. Syncytial knots from idiopathic IUGR had significantly smaller surface area (Z=2.637; P=0.008) and higher density (Z=3.225; P=0.001) compared with the control group, while there is no difference in number of syncytial knots per individual villus, total number of syncytial knots in each placenta sample or number of syncytial nuclei per syncytial knot.

CONCLUSIONS

The investigated histopathologic findings in idiopathic IUGR placentas are incidental, with no higher frequency than in placentas from uncomplicated pregnancies, and should not be considered as possible causative factors for idiopathic IUGR. The demonstrated qualitative changes of syncytial knots in placentas associated with IUGR could represent a compensatory mechanism.

Endovascular trophoblast and preeclampsia: A reassessment

Since the earliest report on impaired spiral artery remodelling in preeclamptic human pregnancies, numerous studies have been devoted to possible mechanisms of impaired trophoblast invasion. A better knowledge of early uteroplacental blood flow has provided a physiological context for the processes of spiral artery invasion and associated remodelling, revealing a closely timed relationship between increasing flow and early steps in vascular remodelling. Concerning the impaired trophoblast invasion in preeclampsia, it has also to be considered that impaired invasion not only concerns invasion depth per se, but also the extension of this deep invasion from the central towards the more lateral spiral arteries of the placental bed. Since also in preeclampsia the very central spiral arteries may be normally invaded, the existence of such spatial gradient provides a further dimension to the problem. A practical consequence is that frequently used rodent models, which show invasion of two or three spiral arteries only, may be less useful for studying this particular aspect of the disease. Amongst non-human primates, baboons and rhesus monkeys are 'shallow invaders', and only in some of the great apes deep trophoblast invasion and associated spiral artery remodelling occurs. A better knowledge of the evolutionary history of deep invasion and its possible selective benefit might ultimately improve our understanding of failed deep invasion and impaired spiral artery remodelling in preeclampsia.

Redox control in mammalian embryo development

The development of an embryo constitutes a complex choreography of regulatory events that underlies precise temporal and spatial control. Throughout this process the embryo encounters ever changing environments, which challenge its metabolism. Oxygen is required for embryogenesis but it also poses a potential hazard via formation of reactive oxygen and reactive nitrogen species (ROS/RNS). These metabolites are capable of modifying macromolecules (lipids, proteins, nucleic acids) and altering their biological functions. On one hand, such modifications may have deleterious consequences and must be counteracted by antioxidant defense systems. On the other hand, ROS/RNS function as essential signal transducers regulating the cellular phenotype. In this context the combined maternal/embryonic redox homeostasis is of major importance and dysregulations in the equilibrium of pro- and antioxidative processes retard embryo development, leading to organ malformation and embryo lethality. Silencing the in vivo expression of pro- and antioxidative enzymes provided deeper insights into the role of the embryonic redox equilibrium. Moreover, novel mechanisms linking the cellular redox homeostasis to gene expression regulation have recently been discovered (oxygen sensing DNA demethylases and protein phosphatases, redox-sensitive microRNAs and transcription factors, moonlighting enzymes of the cellular redox homeostasis) and their contribution to embryo development is critically reviewed.

Pre-eclampsia

Pre-eclampsia remains a leading cause of maternal and perinatal mortality and morbidity. It is a pregnancy-specific disease characterised by de-novo development of concurrent hypertension and proteinuria, sometimes progressing into a multiorgan cluster of varying clinical features. Poor early placentation is especially associated with early onset disease. Predisposing cardiovascular or metabolic risks for endothelial dysfunction, as part of an exaggerated systemic inflammatory response, might dominate in the origins of late onset pre-eclampsia. Because the multifactorial pathogenesis of different pre-eclampsia phenotypes has not been fully elucidated, prevention and prediction are still not possible, and symptomatic clinical management should be mainly directed to prevent maternal morbidity (eg, eclampsia) and mortality. Expectant management of women with early onset disease to improve perinatal outcome should not preclude timely delivery-the only definitive cure. Pre-eclampsia foretells raised rates of cardiovascular and metabolic disease in later life, which could be reason for subsequent lifestyle education and intervention.

Aetiology and physiopathology of preeclampsia and related forms

Preeclampsia, a pregnancy-specific syndrome characterized by hypertension, proteinuria and oedema, resolves on placental delivery. Its pathogenesis is thought to be associated to a hypoxic placenta. Placental hypoxia is responsible for the maternal vascular dysfunction via the increased placental release of anti-angiogenic factors such as soluble flt1 and endoglin. These soluble receptors bind VEGF, PLGF and TGFbeta1 and 3 in the maternal circulation, causing endothelial dysfunction in many maternal tissues. Despite these recent and important new molecular findings, it is important to consider that normal pregnancy is also characterized by systemic inflammation, oxidative stress and alterations in levels of angiogenic factors and vascular reactivity. Both the placenta and maternal vasculatures are major sources of reactive oxygen and nitrogen species which can produce powerful pro-oxidants that covalently modify proteins and alter vascular function in preeclampsia. Finally, the recent demonstration of activating auto-antibodies to the Angiotensin 1 receptor that experimentally play a major pathogenic role in preeclampsia further indicates the pleiotropism of aetiologies of this condition.

First-trimester assessment of placenta function and the prediction of preeclampsia and intrauterine growth restriction

Preeclampsia and intrauterine growth restriction (IUGR) are major contributors to perinatal mortality and morbidity worldwide. Both are characterized by impaired trophoblastic invasion of the maternal spiral arteries and their conversion from narrow muscular vessels to wide non-muscular channels. Despite improvement in the understanding of the pathophysiology of these conditions, ability to accurately identify pregnant woman who will develop them is limited. This greatly impairs the development and testing of preventive interventions. While different measures of placental dysfunction have been associated with increased risk for adverse pregnancy outcomes, the ability of any single one to accurately predict these outcomes is poor. Developing predictive tests is further challenged by difficulty in the timing of the measurements, as both the structural and biochemical characteristics of the placenta change with increasing gestational age. The ideal screening test would accurately predict the development of adverse pregnancy outcomes early enough to provide a window for preventive interventions. Improvement in ultrasound technology provides potentially useful novel tools for evaluating placental structure, but measurements need to be standardized in order to be useful. Maternal serum analyte screening is a noninvasive test of placental biochemical function, but present serum marker alone is not sufficiently accurate to suggest its routine use in clinical practice. The use of first trimester biochemical markers in combination with uterine artery Doppler screening is promising as a potential screening tool. Prospective longitudinal studies using standardized methodology are necessary to further evaluate the choice of parameters and strategies of combination to achieve the best predictive models.

Hypertensive disorders in pregnancy: screening by biophysical and biochemical markers at 11-13 weeks

OBJECTIVE

To examine the performance of screening for pre-eclampsia (PE) and gestational hypertension (GH) by a combination of maternal factors and various biophysical and biochemical markers at 11-13 weeks' gestation.

METHODS

This was a case-control study of 26 cases of early PE, 90 of late PE, 85 of GH and 201 unaffected controls. Maternal history was recorded, the uterine artery with the lowest pulsatility index (L-PI) and mean arterial pressure (MAP) were measured and stored plasma and serum were analyzed for placental growth factor (PlGF), inhibin-A, activin-A, tumor necrosis factor receptor-1, matrix metalloproteinase-9, pentraxin-3 and P-selectin.

RESULTS

Multivariate logistic regression analysis demonstrated that significant prediction for early PE was provided by maternal factors, MAP, uterine artery L-PI and serum PlGF. Significant prediction of late PE was provided by maternal factors, MAP, uterine artery L-PI, PlGF, activin-A and P-selectin. For GH significant prediction was provided by maternal factors, MAP, uterine artery L-PI and activin-A. In screening by a combination of maternal factors, biophysical and biochemical markers the estimated detection rates, at a 5% false-positive rate, were 88.5% (95% CI, 69.8-97.4%) for early PE, 46.7% (95% CI, 36.1-57.5%) for late PE and 35.3% (95% CI, 25.2-46.4%) for GH.

CONCLUSION

Combined biophysical and biochemical testing at 11-13 weeks could effectively identify women at high risk for subsequent development of hypertensive disorders in pregnancy.

Erythrocyte markers of oxidative stress in higher age-group preeclamptic and normal pregnant mothers

Preeclampsia can have significant impact on health of both mother and fetus. It had been proposed that maternal endothelial cell dysfunction is the key event resulting in the diverse clinical manifestations of preeclampsia and evidence has since accumulated. Research in recent times is indicative of the role of oxidative stress in the endothelial cell dysfunction. Preeclampsia is more common in first pregnancy and studies have further shown an increase in risk of preeclampsia with maternal age. The aim of this study was to explore the status of oxidative stress in higher age-group preeclamptic and normal pregnant mother. The study included 20 normal pregnant women and 60 preeclamptic women. They were allocated into 4 subgroups between ages 20-25, 26-30, 31-35, and 36-40. Erythrocytes were analyzed for the following antioxidant enzymes, i.e., glutathione peroxidase, superoxide dismutase and catalase.Lipid peroxidation product, malondialdehyde, was analyzed to determine oxidative stress. The results showed an increase in oxidative stress, and high magnitude suppression/decrease in antioxidant enzymes activities in erythrocytes with increase in age groups in both preeclamptic and normal pregnant women. This indicates that an increase in the risk of preeclampsia with maternal age could be due to an increase in oxidative stress with age. This further attests to the role of oxidative stress in preeclampsia.

Allelic variations in angiogenic pathway genes are associated with preeclampsia

OBJECTIVE

This study investigates the association of allelic variation in angiogenic pathway genes and preeclampsia.

STUDY DESIGN

Data for cases with preeclampsia and term control subjects were collected prospectively. Maternal DNA was extracted, and 124 tagging single nucleotide polymorphisms in 6 genes (vascular endothelial growth factor A, B, and C; fms-like tyrosine kinase 1 and 4; endoglin) were genotyped. Multivariable logistic regression was used to evaluate the association between tagging single nucleotide polymorphisms and preeclampsia; data were controlled for age. All models were evaluated in black women and white women separately. Haplotype analyses were performed.

RESULTS

We analyzed data from 606 women (489 black women [184 cases] and 117 white women [32 cases]). In black women, the fms-like tyrosine kinase 1 rs12584067 (odds ratio [OR], 1.55; 95% confidence interval [CI], 1.01-2.36; P=.05) and rs7335588 (OR, 1.61; 95% CI, 1.06-2.43; P=.01) and the vascular endothelial growth factor C rs1485766 (OR, 1.56; 95% CI, 1.05-2.30; P=.03) and rs6838834 (OR, 1.60; 95% CI, 1.05-2.45; P=.03) single nucleotide polymorphisms were associated with preeclampsia. In white women, the fms-like tyrosine kinase 1 rs722503 (OR, 2.12; 95% CI, 1.07-4.19; P=.03), fms-like tyrosine kinase 4 rs307826 (OR, 3.06; 95% CI, 1.18-7.91; P=.01), and vascular endothelial growth factor C rs7664413 (OR, 2.04; 95% CI, 0.99-4.17; P=.04) single nucleotide polymorphisms were associated with preeclampsia.

CONCLUSION

Allelic variations in the fms-like tyrosine kinase 1 and vascular endothelial growth factor C genes are associated with preeclampsia in both ethnic groups.

The origin of pre-eclampsia: from decidual "hyperoxia" to late hypoxia

Normal gestation implants on a relatively hypoxic deciduas so that trophoblast deeply invades endometrium and angiogenesis seeks for oxygen supply. If implantation occurs before those hypoxic conditions occur, trophoblast invasion is defective, due to the relatively high oxygen tension in the decidual environment, laying the foundations for subsequent pre-eclampsia.

Immune thrombocytopenia in pregnancy

Management of immune thrombocytopenia in pregnancy can be a complex and challenging task and may be complicated by fetal-neonatal thrombocytopenia. Although fetal intracranial hemorrhage is a rare complication of immune thrombocytopenia in pregnancy, invasive studies designed to determine the fetal platelet count before delivery are associated with greater risk than that of fetal intracranial hemorrhage and are discouraged. Moreover, the risk of neonatal bleeding complications does not correlate with the mode of delivery, and cesarean section should be reserved only for obstetric indications.

Maternal plasma pentraxin 3 at 11 to 13 weeks of gestation in hypertensive disorders of pregnancy

OBJECTIVE

To investigate whether in pregnancies that subsequently develop preeclampsia (PE), the maternal plasma concentration of the inflammatory factor pentraxin 3 (PTX3) at 11-13 weeks of gestation is increased and whether such a possible increase is associated with uterine artery pulsatility index (PI).

METHODS

The concentration of plasma PTX3 at 11-13 weeks was measured in a case-control study from 120 pregnancies that developed PE, including 27 who required delivery before 34 weeks (early PE), 87 cases of gestational hypertension (GH) and 207 normal controls. The median PTX3 multiple of the median (MoM) in the control and hypertensive groups were compared. Regression analysis was used to determine the significance of the association between plasma PTX3 and uterine artery PI.

RESULTS

Plasma PTX3 was significantly higher in the early PE group (1.44 MoM; p < 0.0083) but not in late PE (1.11 MoM) or GH (1.10 MoM) compared to the controls (0.97 MoM). There was no significant association between plasma PTX3 levels and uterine artery PI in either the PE group (p = 0.693) or in the controls (p = 0.209).

CONCLUSION

Increase in maternal plasma PTX3 in pregnancies that subsequently develop early PE is evident from 11-13 weeks but the underlying mechanism for such an increase remains uncertain.

Recombinant vascular endothelial growth factor 121 infusion lowers blood pressure and improves renal function in rats with placentalischemia-induced hypertension

Antagonism of vascular endothelial growth factor (VEGF) signaling by soluble fms-like tyrosine kinase 1 occurs during preeclampsia and is proposed to play an important role in the pathogenesis of preeclampsia. We reported recently that hypertension associated with chronic reductions in uteroplacental perfusion pressure (RUPP) is associated with increased soluble fms-like tyrosine kinase 1 and decreased free VEGF. Whether restoration of circulating VEGF can restore renal function and chronically decrease arterial pressure associated with placental ischemia remains unknown. We hypothesized that chronic infusion of VEGF(121) would attenuate hypertension, increase glomerular filtration rate, and reverse the endothelial dysfunction associated with chronic RUPP. VEGF(121) (at either 90 or 180 microg/kg per day) was administered for 5 days via osmotic minipump placed IP. Mean arterial pressure, renal function, and tissues were obtained on day 19 of pregnancy from RUPP+VEGF, RUPP, and normal pregnant dams. Mean arterial pressure was increased in the RUPP (131+/-3 mm Hg) compared with the normal pregnant (102+/-1 mm Hg) rats, and infusion of VEGF(121) resolved the hypertension (105+/-5 mm Hg). Glomerular filtration rate was decreased in the RUPP dams (1.5+/-0.3 mL/min) and restored to normal pregnant levels (3.1+/-0.5 mL/min) by VEGF(121) treatment (3.1+/-0.4 mL/min). Effective renal plasma flow, decreased by RUPP, was also increased by VEGF(121) infusion. Relaxation to acetylcholine was enhanced by the VEGF treatment (P<0.05). These data demonstrate that chronic infusion of VEGF(121) during late gestation restores glomerular filtration rate and endothelial function and reduces high blood pressure associated with placental ischemia. The present results suggest that VEGF(121) may be a candidate molecule for management of preeclampsia and its related complications.

Intrauterine Growth Restriction in Spontaneously Hypertensive Rats

We examined the test profile of changes in systolic blood pressure (SBP), urinary volume, urinary sodium, and protein excretion in normotensive (Sprague Dawley) and spontaneously hypertensive rats (SHR) up to the 18th day of pregnancy. On days 6, 11, and 18 of pregnancy, the number of implantation sites, number of embryos, litter size, placenta, and litter weight were determined. In SHR, SBP (mmHg) increased significantly from the start of the test and remained high throughout the experiment. There was also a significant increase in urine volume (mL per 24 hrs) and urinary sodium excretion (mEq per 24 hrs) but no significant changes in protein excretion rate. The number of implantation sites on day 6 of pregnancy and the number of embryos on day 11 were similar in both groups. Uterus weight in SHR on days 6 and 11 of pregnancy was significantly lower than in normotensive rats. On day 18 of pregnancy in SHR, a substantial decrease in litter weight (7.10 +/- 0.40 vs. 12.00 +/- 0.92 g; p < 0.001) and weight of placenta (2.35 +/- 0.07 vs. 4.74 +/- 0.21 g; p < 0.001) was observed, with no modification in litter size. The hypertension associated with pregnancy in SHR increased urine volume and urinary sodium excretion and decreased weight of uterus, litter, and placenta relative to control rats.

Chymotrypsin-like protease (chymase) mediates endothelial activation by factors derived from preeclamptic placentas

Endothelial cells (EC) activation is an important inflammatory phenotypic change in the vascular system in women with preeclampsia (PE). In PE, maternal vessel chymotrypsin-like protease (CLP)/chymase expression was increased. Chymase is an inflammatory protease. In this study, we specifically examined whether placental-derived CLP could induce EC activation and whether EC activation is associated with increased cellular protease expression. Human uterine microvascular endothelial cells (UtMVECs) were used. Endothelial activation was determined by endothelial adhesion molecule P-selectin, E-selectin, inter-cellular adhesion molecule (ICAM), and vascular cell adhesion molecule (VCAM) expressions and by extracellular regulated kinase (ERK) activity. Activation of endogenous CLP/chymase associated with ERK phosphorylation was further examined by CLP/chymase short interfering RNA (siRNA). Our results showed that cells treated with PE placental conditioned medium revealed increased P-selectin, E-selectin, and VCAM-1 expressions and increased ERK phosphorylation. Increased endothelial adhesion molecule expression and phosphorylated ERK (pERK) induction could be attenuated or abolished by depletion of CLP in the conditioned medium or by transfecting ECs with CLP/chymase siRNA. These observations suggest that placental-derived CLP/chymase is responsible for inducing endothelial inflammatory phenotypic changes possibly by upregulation of cell adhesion molecule expressions, activation of cellular protease, and induction of ERK phosphorylation. We speculate that activation of endothelial CLP/chymase may directly relate to the increased inflammatory phenotypic changes in the vascular system in women with PE.

Differential expression profile of microRNAs in human placentas from preeclamptic pregnancies vs normal pregnancies

OBJECTIVE

The purpose of this study was to perform a comprehensive analysis of the microRNA expression profile in placentas from preeclamptic pregnancies vs normal placentas.

STUDY DESIGN

Placentas were obtained from patients with (1) mild preeclampsia (n = 8) and (2) severe preeclampsia (n = 15) and (3) in a normal control group (n = 11) with elective cesarean delivery. The microRNA expression profile was assessed by microRNA microarray and real-time reverse transcriptase-polymerase chain reaction analysis.

RESULTS

Thirty-four microRNAs were expressed differentially in preeclamptic placentas, compared with normal placentas. Of these, 11 microRNAs were overexpressed, and 23 microRNAs were underexpressed in preeclamptic pregnancies. Notably, several microRNA clusters on human chromosome 19q13.42, 13q31.3, Xq26.2, Xq26.3, and 14q32.31 (a human imprinted region) were expressed differentially in preeclamptic placentas. These results were confirmed with the use of real-time polymerase chain reaction for selected microRNAs (miR-210, -152, -411, and so on).

CONCLUSION

The results show that 34 microRNAs are deregulated in preeclamptic pregnancies, which suggests the involvement of these microRNAs in the pathogenesis of preeclampsia.

Reducing stillbirths: prevention and management of medical disorders and infections during pregnancy

BACKGROUND

An estimated two-thirds of the world's 3.2 million stillbirths occur antenatally, prior to labour, and are often overlooked in policy and programs. Poorly recognised, untreated or inadequately treated maternal infections such as syphilis and malaria, and maternal conditions including hypertensive disorders, are known risk factors for stillbirth.

METHODS

We undertook a systematic review of the evidence for 16 antenatal interventions with the potential to prevent stillbirths. We searched a range of sources including PubMed and the Cochrane Library. For interventions with prior Cochrane reviews, we conducted additional meta-analyses including eligible newer randomised controlled trials following the Cochrane protocol. We focused on interventions deliverable at the community level in low-/middle-income countries, where the burden of stillbirths is greatest.

RESULTS

Few of the studies we included reported stillbirth as an outcome; most that did were underpowered to assess this outcome. While Cochrane reviews or meta-analyses were available for many interventions, few focused on stillbirth or perinatal mortality as outcomes, and evidence was frequently conflicting. Several interventions showed clear evidence of impact on stillbirths, including heparin therapy for certain maternal indications; syphilis screening and treatment; and insecticide-treated bed nets for prevention of malaria. Other interventions, such as management of obstetric intrahepatic cholestasis, maternal anti-helminthic treatment, and intermittent preventive treatment of malaria, showed promising impact on stillbirth rates but require confirmatory studies. Several interventions reduced known risk factors for stillbirth (e.g., anti-hypertensive drugs for chronic hypertension), yet failed to show statistically significant impact on stillbirth or perinatal mortality rates. Periodontal disease emerged as a clear risk factor for stillbirth but no interventions have reduced stillbirth rates.

CONCLUSION

Evidence for some newly recognised risk factors for stillbirth, including periodontal disease, suggests the need for large, appropriately designed randomised trials to test whether intervention can minimise these risks and prevent stillbirths. Existing evidence strongly supports infection control measures, including syphilis screening and treatment and malaria prophylaxis in endemic areas, for preventing antepartum stillbirths. These interventions should be incorporated into antenatal care programs based on attributable risks and burden of disease.

Oxidative stress contributes to soluble fms-like tyrosine kinase-1 induced vascular dysfunction in pregnant rats

BACKGROUND

Recent evidence indicates that both increased oxidative stress and an altered balance between pro- and anti-angiogenic factors such as vascular-endothelial growth factor (VEGF) and the soluble VEGF receptor (sFlt-1) contribute to endothelial dysfunction in preeclampsia. We hypothesized that chronic infusion of sFlt-1 to mimic the increase observed in preeclamptic patients would reduce plasma VEGF concentrations, increase blood pressure (BP) and vascular superoxide levels, and cause endothelial dysfunction in the pregnant rat.

METHODS

Recombinant sFlt-1 was infused (500 ng/h) during days 13-18 of pregnancy. BP, fetal and placental weight, oxidative stress and vessel vasorelaxation were determined on day 18 of pregnancy.

RESULTS

Plasma sFlt-1 concentrations (299 +/- 33 vs. 100 +/- 16 pg/ml; P < 0.01) and BP (117 +/- 6 vs. 98 +/- 4 mm Hg; P < 0.01) were increased, while plasma-free VEGF concentrations (570 +/- 77 vs. 780 +/- 48 pg/ml; P < 0.01) were decreased when compared to vehicle infused dams. sFlt-1 rats had smaller fetuses (1.3 +/- 0.03 vs. 1.5 +/- 0.04 g, P < 0.01) and placentas (0.41 +/- 0.01 vs. 0.47 +/- 0.02 g; P < 0.05). Placental (180 +/- 66 vs. 24 +/- 2.3 RLU/min/mg; P < 0.05) and vascular (34 +/- 8 vs. 12 +/- 5 RLU/min/mg; P < 0.05) superoxide production was increased in the sFlt-1 compared to vehicle infused rats. Vasorelaxation to acetylecholine (ACh) and sodium nitroprusside (SNP) were both decreased (P < 0.05) in the sFlt-1 infusion group compared to the vehicle and this decrease was attenuated (P < 0.05) by the superoxide scavenger Tiron.

CONCLUSION

These data indicate elevated maternal sFlt-1 and decreased VEGF concentrations results in increased oxidative stress that contributes to vascular dysfunction during pregnancy.

Maternal exposure to folic acid antagonists and placenta-mediated adverse pregnancy outcomes

BACKGROUND

In previous studies, maternal exposure to folic acid antagonists was associated with increased risks of neural tube defects, cardiovascular defects, oral clefts and urinary tract defects. The objective of the current study was to assess the possible effects of using folic acid antagonists in pregnancy on placenta-mediated adverse outcomes of pregnancy.

METHODS

We used data from an administrative database to retrospectively compare the occurrence of placenta-mediated adverse pregnancy outcomes between pregnant women exposed to folic acid antagonists and women without exposure to these agents.

RESULTS

We included in the analysis a total of 14 982 women who had been exposed to folic acid antagonists and 59 825 women who had not been exposed. Sulfamethoxazole-trimethoprim was the most frequently prescribed dihydrofolate reductase inhibitor (a total of 12 546 exposures during the preconception period and all 3 trimesters), and phenobarbital was the most frequently prescribed among the other folic acid antagonists (a total of 1565 exposures). The risks of preeclampsia (adjusted odds ratio [OR] 1.52, 95% confidence interval [CI] 1.39-1.66), severe preeclampsia (OR 1.77, 95% CI 1.38-2.28), placental abruption (OR 1.32, 95% CI 1.12-1.57), fetal growth restriction defined as less than the 10th percentile (OR 1.07, 95% CI 1.01-1.13), fetal growth restriction defined as less than the 3rd percentile (OR 1.22, 95% CI 1.11-1.34) and fetal death (OR 1.35, 95% CI 1.07-1.70) were greater among mothers with exposure to folic acid antagonists. In general, the risks associated with exposure to other folic acid antagonists were higher than those associated with exposure to dihydrofolate reductase inhibitors. Supplementary analyses involving tight matching with propensity score, restriction of the analysis to women with exposure during the first and second trimesters and restriction of the analysis to specific categories of folic acid antagonists yielded similar results.

INTERPRETATION

Maternal exposure to folic acid antagonists appears to increase the risk of placenta-mediated adverse outcomes of pregnancy.

First-trimester maternal serum tumor necrosis factor receptor-1 and pre-eclampsia

OBJECTIVES

To examine whether the maternal serum concentration of the soluble receptor-1 of tumor necrosis factor-alpha (TNF-R1) at 11-13 weeks of gestation in pregnancies that subsequently develop pre-eclampsia is different from that in women without this complication.

METHODS

The concentration of TNF-R1 at 11 + 0 to 13 + 6 weeks was measured in samples from 128 cases that subsequently developed pre-eclampsia and 569 controls with no pregnancy complications. TNF-R1 and uterine artery pulsatility index (UtA-PI) values were expressed as multiples of the median (MoM) adjusted for maternal factors. The distributions of log TNF-R1 MoM and log UtA-PI MoM in the control and pre-eclampsia groups were compared. Logistic regression analysis was used to determine whether a significant contribution is provided by maternal factors, TNF-R1 and UtA-PI in predicting pre-eclampsia. The performance of screening was determined by analysis of receiver-operating characteristics curves.

RESULTS

Median TNF-R1 and UtA-PI were significantly higher in the pre-eclampsia group (TNF-R1, 1.062 MoM; UtA-PI, 1.301 MoM) than in the control group (TNF-R1, 0.996 MoM; UtA-PI, 1.037 MoM). There was no significant association between TNF-R1 and gestational age at delivery, birth weight percentile or UtA-PI. Logistic regression analysis demonstrated significant contributions to the detection of pre-eclampsia from maternal factors and UtA-PI but not from TNF-R1.

CONCLUSIONS

In pregnancies developing pre-eclampsia the maternal serum TNF-R1 concentration at 11-13 weeks of gestation is increased, but the level of TNF-R1 is not associated with the degree of impairment in placental perfusion or the severity of pre-eclampsia. Measurement of serum TNF-R1 does not improve the prediction of pre-eclampsia provided by screening based on a combination of maternal factors and UtA-PI.

Hypertension produced by placental ischemia in pregnant rats is associated with increased soluble endoglin expression

Recent clinical studies indicate that an excess of angiostatic factors, such as soluble endoglin (sEng), is related to the occurrence of preeclampsia. Although recent clinical studies report that sEng is increased in preeclamptic women, the mechanisms underlying its overexpression remain unclear. Evidence suggests that hypoxia and induction of heme oxygenase-1 have opposing effects on sEng expression, the former stimulatory and the latter inhibitory. Hence, we hypothesized that placental ischemia because of reduced uterine perfusion pressure (RUPP) in the pregnant rat would increase sEng expression and decrease heme oxygenase-1. Mean arterial pressure was obtained via arterial catheter, and serum and placental proteins were measured by Western blot. Mean arterial pressure was increased (132+/-3 mm Hg versus 102+/-2 mm Hg; P<0.001), and fetal (2.35+/-0.05 g versus 1.76+/-0.08 g; P<0.001) and placental weight were decreased (0.47+/-0.04 g versus 0.58+/-0.03 g; P<0.01) in the RUPP compared with normal pregnant controls. Serum sEng (0.10+/-0.02 arbitrary pixel units [apu] versus 0.05+/-0.01 apu; P<0.05) and placental endoglin (4.7+/-2.3 apu versus 1.45+/-0.42 apu; P<0.05) were increased along with placental hypoxia inducible factor-1 alpha (1.42+/-0.25 apu versus 0.68+/-0.09 apu; P<0.05) expression in the RUPP versus the normal pregnant dams. Placental HO-1 (1.4+/-0.3 apu versus 2.5+/-0.1 apu; P<0.05) expression decreased in the RUPP compared with normal pregnant dams. The present findings support our hypothesis that placental ischemia because of RUPP increases the expression of sEng and shifts the balance of angiogenic factors in the maternal circulation toward an angiostatic state. The present study provides further evidence that placental ischemia is a strong in vivo stimulus of angiostatic factors during pregnancy.

Leptin expression in primary trophoblast cells in response to incubation with the serum of preeclamptic women

OBJECTIVE

We investigated whether the increase of leptin expression in preeclamptic placentas is additionally influenced by soluble maternal factors under hypoxic and nonhypoxic conditions.

METHODS

Term trophoblast cells were isolated and stimulated with sera from preeclamptic women under normoxic or hypoxic conditions. Levels of leptin mRNA and protein were evaluated by real-time RT-PCR or ELISA and Western blot analysis.

RESULTS

Leptin concentrations were increased in the serum of patients with preeclampsia and gestational diabetes. Hypoxia, insulin, and dexamethasone induced leptin expression in trophoblast cells. The incubation with sera from preeclamptic women led to a small, though, significant, increase of leptin gene expression. The effect of preeclamptic serum on leptin gene expression in trophoblast cells was lost under hypoxia. The serum of women with gestational diabetes did not increase leptin expression neither in normoxic nor hypoxic primary trophoblast cells.

CONCLUSION

Our results can not exclude a soluble maternal factor in the serum of women with preeclampsia accounting for increased leptin expression in placental tissue in addition to hypoxia. However, an important biological role of this small increase in nonhypoxic conditions does not seem very likely.

Differential placental gene expression in preeclampsia

OBJECTIVE

Candidate genes that are associated with preeclampsia have not been described fully. We conducted microarray and confirmatory quantitative real time polymerase chain reaction studies to investigate global placental gene expression in preeclampsia.

STUDY DESIGN

RNA was extracted from placental samples that were collected from 18 preeclampsia cases and 18 normotensive control subjects. Oligonucleotide probes that represented 22,000 genes were used to measure gene expression in each sample. Differential gene expression was evaluated with the Student t test, fold change assessment, and significance analysis of microarrays. Functions and functional relationships of differentially expressed genes were evaluated.

RESULTS

Genes (n = 58) that participated in immune system, inflammation, oxidative stress, signaling, growth, and development pathways were expressed differentially in preeclampsia. These genes included previously described candidate genes (such as leptin), potential candidate genes with related functions (such as CYP11A) and novel genes (such as CDKN1C).

CONCLUSION

Expression of genes (both candidate and novel) with diverse functions is associated with preeclampsia risk, which reflects the complex pathogenesis.

Pathophysiology of hypertension in response to placental ischemia during pregnancy: a central role for endothelin?

BACKGROUND

Preeclampsia is new-onset hypertension with proteinuria during pregnancy. The initiating event in preeclampsia has been postulated to involve reduced placental perfusion, which leads to widespread dysfunction of the maternal vascular endothelium.

OBJECTIVE

The main objective of this brief review was to highlight some of the recent advances in our understanding of the mechanisms whereby the endothelin (ET) system, via ET type A (ETA) receptor activation, modulates blood pressure in preeclamptic women and in animal models of pregnancy-related hypertension.

METHODS

This review focused on the role of ET and tumor necrosis factor-alpha (TNF-alpha) in preeclampsia, with emphasis on the pathophysiology of hypertension in response to placental ischemia in animal models of pregnancy. Relevant published data were identified by searching PubMed and supplemented with contributions from our laboratory.

RESULTS

Studies in preeclamptic women indicate that their hypertension is associated with increases in ET synthesis. Recent studies in pregnant rats indicate that the ET system is activated in response to reductions in uterine perfusion pressure and to chronic elevations in serum TNF-alpha concentrations. In these 2 animal models, the findings also suggest that ET A receptor activation may play a role in mediating hypertension.

CONCLUSIONS

Although recent studies in animal models implicate an important role for the ET system in preeclampsia, the usefulness of selective ET A receptor antagonists for the treatment of hypertension in women with preeclampsia remains unclear. This important question will not be answered until well-controlled clinical studies using specific ET A receptor antagonists are conducted for women with preeclampsia.

Vitamins C and E inhibit apoptosis of cultured human term placenta trophoblast

Preeclampsia can be lethal to both mother and baby. The prominent symptoms of this syndrome are hypertension, proteinuria and oedema, resulting from an exaggerated aseptic systemic inflammatory response, triggered by placental factors shed into the maternal circulation. Syncytiotrophoblast microparticles (STBM) are one possible factor, shed when the placenta is exposed to stressors such as hypoxia/reperfusion. These can disrupt mitochondria, triggering apoptosis and necrosis, placental pathologies which are increased in preeclampsia. We tested the effects of antioxidant vitamins C (50 microM) and E (50 microM) on trophoblast in culture, using term villous cytotrophoblast preparations. Following Percoll gradient centrifugation and MHC class I expressing cell depletion of placenta digests, syncytial fragments were removed using anti-placental alkaline phosphatase antibody. This yielded cytotrophoblasts of consistently high purity. EGF (10 ng/ml) stimulated syncytialisation and hCG and progesterone production. However, mitochondrial induced apoptosis (MIA) was evident 96h post-isolation, as mitochondrial membrane potential loss and caspase 9 and caspase 3 activation. ROCK-1 cleavage and syncytiotrophoblast particle shedding increased concurrently with apoptosis induction. Vitamins blocked MIA and syncytiotrophoblast particle shedding and significantly increased hCG (p<0.005) and progesterone (p<0.02) concentrations in culture supernatants, reflecting the increased survival rates. Although more cells survived in culture, syncytialisation rate (%) was significantly reduced (p<0.005). We conclude that vitamins C and E can significantly reduce mitochondrial damage generated following syncytialisation in vitro. However, further work is required to determine whether antioxidant vitamins interfere with normal fusion processes.

NK cell tolerance and the maternal-fetal interface

Natural killer (NK) cells play a fundamental role in the innate immune response through their ability to secrete cytokines and kill target cells without prior sensitization. These effector functions are central to NK cell anti-viral and anti-tumor abilities. Due to their cytotoxic nature, it is vital that NK cells have the capacity to recognize normal self-tissue and thus prevent their destruction. In addition to their role in host defense, NK cells accumulate at the maternal-fetal interface and are thought to play a critical role during pregnancy. The close proximity of uterine NK (uNK) cells to fetal trophoblast cells of the placenta would seemingly lead to catastrophic consequences, as the trophoblast cells are semi-allogeneic. A fundamental enigma of pregnancy is that the fetal cells constitute an allograft but, in normal pregnancies, they are in effect not perceived as foreign and are not rejected by the maternal immune system. Although the mechanisms involved in achieving NK cell tolerance are becoming increasingly well-defined, further clarification is required, given the clinical implications of this work in the areas of infection, transplantation, cancer and pregnancy. Herein, we discuss several mechanisms of NK cell tolerance and speculate as to how they may apply to uNK cells at the maternal-fetal interface.

The genetic aspects of pre-eclampsia: achievements and limitations

Pre-eclampsia, a life-threatening disease during pregnancy, is a leading cause of global maternal mortality. Although there is substantial evidence of a genetic background, the complexity of the processes involved and nature of the maternal-fetal phenomenon do not make the search for the causative genes easy. Recent retrospective studies on the subject suggest the heritable allelic variations, particularly the utero-placental renin-angiotensin system with defective placental vascular development, could become the cornerstone for the genetics of pre-eclampsia and hence might well be associated with such defective development. Moreover, the role of immune mechanisms (immune maladaptation) deserves not to be ignored. Large-scale studies entailing genomewide scanning, sib-pair linkage analysis, and family-based association studies with appropriate power to detect genes with a lower relative risk are necessary to understand the puzzle of the disease. Moreover, recently, the importance of epigenetic features and the effect of imprinted genes related to trophoblast growth as well as fetal development on hypertension in pregnancy have been highlighted. All these possibilities are intuitively attractive and are supported by some circumstantial evidence. Although the consistent tenor of a series of papers instill some confidence, we need meticulously designed larger-scale investigations including large numbers of affected women and their babies to provide the analytic stringency essential to study the polygenic multifactorial basis of pre-eclampsia.

Under-expression of CD24 in pre-eclamptic placental tissues determined by quantitative real-time RT-PCR

BACKGROUND

Pre-eclampsia is a pregnancy-related disorder present in about 5-7% of all pregnancies. CD24 expression was recently reported in different diseases, while it has not yet been determined in pre-eclamptic placental tissues.

METHODS

We collected placental tissues from pre-eclamptic (n = 16) and healthy pregnancies (n = 16). We used the quantitative real-time PCR method with a primer-probe system for determination of CD24 gene expression.

RESULTS

We measured CD24 concentrations of 18.94 +/- 26.86 ng/microl in the pre-eclamptic and 53.85 +/- 92.05 ng/microl in the healthy placental tissues (p = 0.03).

CONCLUSIONS

The quantitative real-time PCR method is suitable to determine CD24 expression in placental tissues. We suppose the low expression of CD24 may cause the enhanced immune reaction and could play a role in the abnormal development of placenta in pre-eclampsia.

Preeclampsia: a danger growing in disguise

Preeclampsia occurs in 3-14% of pregnancies and is defined by maternal hypertension with proteinurea, generally associated with edema, coagulation abnormalities, and disseminated intravascular coagulation. The conditions can lead to eclampsia, characterized by hyperreflexia and convulsions. Several organs are afflicted by the condition, most importantly the liver and kidneys. The direct cause of preeclampsia is unknown, but the initial events are linked to abnormalities of placentation. This implies abnormalities in trophoblast invasion and in physiological alterations of placental vessels required for adequate perfusion of the placenta, which leads to ischemia. The mechanisms that link the ischemic placenta to endothelial lesions and to stimulation of vasoconstrictors and inhibition of vasodilators are still subject of speculation. The only treatment of preeclampsia is delivery. Lowering of blood pressure and prevention of eclampsia with magnesium sulfate is indicated in severe preeclampsia. Despite numerous studies attempting to elucidate the exact etiopathogenesis of this complex multifactorial disease, prediction or prevention methods of preeclampsia are not available.

Preeclamptic sera induce nephrin shedding from podocytes through endothelin-1 release by endothelial glomerular cells

In preeclampsia (PE), proteinuria has been associated with a reduced expression of nephrin by podocytes. In the present study, we investigated in vitro on human cultured podocytes the mechanism responsible for nephrin loss in PE. Sera from patients with PE did not directly downregulate the expression of nephrin. In contrast, conditioned medium obtained from glomerular endothelial cells incubated with PE sera induced loss of nephrin and synaptopodin, but not of podocin, from podocytes. Nephrin loss was related to a rapid shedding of the protein from the cell surface due to cleavage of its extracellular domain by proteases and to cytoskeleton redistribution. The absence of nephrin mRNA downregulation together with nephrin reexpression within 24 h confirm that the loss of nephrin was not related to a reduced synthesis. Studies with an endothelin-1 (ET-1) receptor antagonist that abrogated the loss of nephrin triggered by glomerular endothelial conditioned medium of PE sera indicated that ET-1 was the main effector of nephrin loss. Indeed, ET-1 was synthesized and released from glomerular endothelial cells when incubated with PE sera, and recombinant ET-1 triggered nephrin shedding from podocytes. Moreover, VEGF blockade induced ET-1 release from endothelial cells, and in turn the conditioned medium obtained triggered nephrin loss. In conclusion, the present study identifies a potential mechanism of nephrin loss in PE that may link endothelial injury with enhanced glomerular permeability.

Anticoagulant therapy and pregnancy

Low dose aspirin therapy is one of the anticoagulant treatments used during pregnancy. Anticoagulant agents may be useful for several disorders, such as recurrent miscarriage, pre-eclampsia, fetal growth restriction and infertility. However, it is unclear whether anticoagulant therapy can increase the live birth rate in all of these cases. Recent data suggest that a low-dose aspirin and heparin combination therapy is effective in the prevention of recurrent pregnancy loss in women with antiphospholipid syndrome. Thrombogenic diseases, for example, protein C deficiency, protein S deficiency, factor XII deficiency and hyperhomocysteinemia, may cause pregnancy loss. The etiology of recurrent miscarriage is often unclear and may be multifactorial, with much controversy regarding diagnosis and treatment. Although 70% of recurrent pregnancy losses are unexplained, anticoagulant therapy is effective in maintaining pregnancy without antiphospholipid antibody syndrome. We conclude that a low-dose aspirin and heparin combination therapy can be useful for unexplained cases of recurrent pregnancy loss without antiphospholipid antibody syndrome. (Reprod Med Biol 2008; 7: 1-10).

Circulating microparticles in normal pregnancy and pre-eclampsia

Cellular particles may be larger shed microparticles (>or=100 nm, MPs) that are the products of cell activation or necrosis. There are also smaller endocytic nanoparticles (<100 nm), called exosomes, which are internal vesicles of late endosomes or multivesicular bodies and are released into the extracellular milieu upon fusion of the multivesicular body with the cell surface. Both MPs and exosomes can be detected in the circulations of non-pregnant and pregnant women. In the former MPs are increased in conditions associated with systemic inflammation such as sepsis or metabolic syndrome. During normal pregnancy MPs are increased and they increase further with pre-eclampsia. They include not only MPs derived from platelets, endothelium and various leukocytes but also syncytiotrophoblast derived MPs (often called STBMs). STBMs interact with both immune and endothelial cells and may contribute to the systemic inflammation of both normal and pre-eclamptic pregnancies. However inhibitory activity has also been ascribed to trophoblast derived exosomes. In vitro, they down-regulate T cell activity, a T cell change that has been repeatedly observed, ex vivo, during normal pregnancy.

Pathophysiology of hypertension during preeclampsia: linking placental ischemia with endothelial dysfunction

Studies over the last decade have provided exciting new insights into potential mechanisms underlying the pathogenesis of preeclampsia. The initiating event in preeclampsia is generally regarded to be placental ischemia/hypoxia, which in turn results in the elaboration of a variety of factors from the placenta that generates profound effects on the cardiovascular system. This host of molecules includes factors such as soluble fms-like tyrosine kinase-1, the angiotensin II type 1 receptor autoantibody, and cytokines such as tumor necrosis factor-alpha, which generate widespread dysfunction of the maternal vascular endothelium. This dysfunction manifests as enhanced formation of factors such as endothelin, reactive oxygen species, and augmented vascular sensitivity to angiotensin II. Alternatively, the preeclampsia syndrome may also be evidenced as decreased formation of vasodilators such as nitric oxide and prostacyclin. Taken together, these alterations cause hypertension by impairing renal pressure natriuresis and increasing total peripheral resistance. Moreover, the quantitative importance of the various endothelial and humoral factors that mediate vasoconstriction and elevation of arterial pressure during preeclampsia remains to be elucidated. Thus identifying the connection between placental ischemia/hypoxia and maternal cardiovascular abnormalities in hopes of revealing potential therapeutic regimens remains an important area of investigation and will be the focus of this review.