Histomorphometry of the human placenta in maternal preeclampsia

Disorders of placental villous maturation are present in one-third of cases with spontaneous preterm labor

OBJECTIVES

Spontaneous preterm labor is an obstetrical syndrome accounting for approximately 65-70% of preterm births, the latter being the most frequent cause of neonatal death and the second most frequent cause of death in children less than five years of age worldwide. The purpose of this study was to determine and compare to uncomplicated pregnancies (1) the frequency of placental disorders of villous maturation in spontaneous preterm labor; (2) the frequency of other placental morphologic characteristics associated with the preterm labor syndrome; and (3) the distribution of these lesions according to gestational age at delivery and their severity.

METHODS

A case-control study of singleton pregnant women was conducted that included (1) uncomplicated pregnancies (controls, n=944) and (2) pregnancies with spontaneous preterm labor (cases, n=438). All placentas underwent histopathologic examination. Patients with chronic maternal diseases (e.g., chronic hypertension, diabetes mellitus, renal disease, thyroid disease, asthma, autoimmune disease, and coagulopathies), fetal malformations, chromosomal abnormalities, multifetal gestation, preeclampsia, eclampsia, preterm prelabor rupture of the fetal membranes, gestational hypertension, gestational diabetes mellitus, and HELLP (hemolysis, elevated liver enzymes and low platelet count) syndrome were excluded from the study.

RESULTS

Compared to the controls, the most prevalent placental lesions among the cases were the disorders of villous maturation (31.8% [106/333] including delayed villous maturation 18.6% [62/333] vs. 1.4% [6/442], q<0.0001, prevalence ratio 13.7; and accelerated villous maturation 13.2% [44/333] vs. 0% [0/442], q<0.001). Other lesions in decreasing order of prevalence included hypercapillarized villi (15.6% [68/435] vs. 3.5% [33/938], q<0.001, prevalence ratio 4.4); nucleated red blood cells (1.1% [5/437] vs. 0% [0/938], q<0.01); chronic inflammatory lesions (47.9% [210/438] vs. 29.9% [282/944], q<0.0001, prevalence ratio 1.6); fetal inflammatory response (30.1% [132/438] vs. 23.2% [219/944], q<0.05, prevalence ratio 1.3); maternal inflammatory response (45.5% [195/438] vs. 36.1% [341/944], q<0.01, prevalence ratio 1.2); and maternal vascular malperfusion (44.5% [195/438] vs. 35.7% [337/944], q<0.01, prevalence ratio 1.2). Accelerated villous maturation did not show gestational age-dependent association with any other placental lesion while delayed villous maturation showed a gestational age-dependent association with acute placental inflammation (q-value=0.005).

CONCLUSIONS

Disorders of villous maturation are present in nearly one-third of the cases of spontaneous preterm labor.

Placental Oxidative Stress: From Miscarriage to Preeclampsia

OBJECTIVE

To review the role of oxidative stress in two common placental-related disorders of pregnancy, miscarriage and preeclampsia.

METHODS

Review of published literature.

RESULTS

Miscarriage and preeclampsia manifest at contrasting stages of pregnancy, yet both have their roots in deficient trophoblast invasion during early gestation. Early after implantation, endovascular trophoblast cells migrate down the lumens of spiral arteries, and are associated with their physiological conversion into flaccid conduits. Initially these cells occlude the arteries, limiting maternal blood flow into the placenta. The embryo therefore develops in a low oxygen environment, protecting differentiating cells from damaging free radicals. Once embryogenesis is complete, the maternal intervillous circulation becomes fully established, and intraplacental oxygen concentration rises threefold. Onset of the circulation is normally a progressive periphery-center phenomenon, and high levels of oxidative stress in the periphery may induce formation of the chorion laeve. If trophoblast invasion is severely impaired, plugging of the spiral arteries is incomplete, and onset of the maternal intervillous circulation is premature and widespread throughout the placenta. Syncytiotrophoblastic oxidative damage is extensive, and likely a major contributory factor to miscarriage. Between these two extremes will be found differing degrees of trophoblast invasion compatible with ongoing pregnancy but resulting in deficient conversion of the spiral arteries and an ischemia-reperfusion-type phenomenon. Placental perfusion will be impaired to a greater or lesser extent, generating commensurate placental oxidative stress that is a major contributory factor to preeclampsia.

CONCLUSION

Miscarriage, missed miscarriage, and early- and late-onset preeclampsia represent a spectrum of disorders secondary to deficient trophoblast invasion.

Placental origins of adverse pregnancy outcomes: potential molecular targets: an Executive Workshop Summary of the Eunice Kennedy Shriver National Institute of Child Health and Human Development

Although much progress is being made in understanding the molecular pathways in the placenta that are involved in the pathophysiology of pregnancy-related disorders, a significant gap exists in the utilization of this information for the development of new drug therapies to improve pregnancy outcome. On March 5-6, 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health sponsored a 2-day workshop titled Placental Origins of Adverse Pregnancy Outcomes: Potential Molecular Targets to begin to address this gap. Particular emphasis was given to the identification of important molecular pathways that could serve as drug targets and the advantages and disadvantages of targeting these particular pathways. This article is a summary of the proceedings of that workshop. A broad number of topics were covered that ranged from basic placental biology to clinical trials. This included research in the basic biology of placentation, such as trophoblast migration and spiral artery remodeling, and trophoblast sensing and response to infectious and noninfectious agents. Research findings in these areas will be critical for the formulation of the development of future treatments and the development of therapies for the prevention of a number of pregnancy disorders of placental origin that include preeclampsia, fetal growth restriction, and uterine inflammation. Research was also presented that summarized ongoing clinical efforts in the United States and in Europe that has tested novel interventions for preeclampsia and fetal growth restriction, including agents such as oral arginine supplementation, sildenafil, pravastatin, gene therapy with virally delivered vascular endothelial growth factor, and oxygen supplementation therapy. Strategies were also proposed to improve fetal growth by the enhancement of nutrient transport to the fetus by modulation of their placental transporters and the targeting of placental mitochondrial dysfunction and oxidative stress to improve placental health. The roles of microRNAs and placental-derived exosomes, as well as messenger RNAs, were also discussed in the context of their use for diagnostics and as drug targets. The workshop discussed the aspect of safety and pharmacokinetic profiles of potential existing and new therapeutics that will need to be determined, especially in the context of the unique pharmacokinetic properties of pregnancy and the hurdles and pitfalls of the translation of research findings into practice. The workshop also discussed novel methods of drug delivery and targeting during pregnancy with the use of macromolecular carriers, such as nanoparticles and biopolymers, to minimize placental drug transfer and hence fetal drug exposure. In closing, a major theme that developed from the workshop was that the scientific community must change their thinking of the pregnant woman and her fetus as a vulnerable patient population for which drug development should be avoided, but rather be thought of as a deprived population in need of more effective therapeutic interventions.

[Histological hanges in the placenta and vascularization of its villi in early- and late-onset preeclampsia]

AIM

to make a comparative histological study of the placenta and a morphometric analysis of its terminal villi in early- and late-onset preeclampsia.

MATERIAL AND METHODS

Placentae from patients whose pregnancy had been complicated by the development of early- (n=26) or late-onset (n=84) preeclampsia were examined. A control group comprised placentae from 28 patients with physiological pregnancy and no extragenital diseases. The authors made a comparative histological study of placental tissue and a morphometric analysis of the terminal villi using the sections immunohistochemically stained for CD31.

RESULTS

It was determined that there was a preponderance of branching angiogenesis in the preeclamptic chorionic villi and an increase in the number of syncytial nodules and microcysts in the septae in late-onset preeclampsia. Morphometric analysis of immunohistochemical placental specimens established a reduction in the sizes and vascularization indicators of terminal villi that determine the development of placental hypoxia and are more pronounced in cases of early-onset preeclampsia.

Size at birth and risk of breast cancer: update from a prospective population-based study

Birth size variables (birth weight, birth length and head circumference) have been reported to be positively associated with adult breast cancer risk, whereas a possible association of placental weight has not been adequately studied. It has also been suggested that maternal height may modify the association of birth size with adult breast cancer risk, but this has not been studied in detail. We updated a long-term follow-up of 22,931 Norwegian women (average of 51 years of follow up during which 870 women were diagnosed with breast cancer) and assessed placental weight in relation to breast cancer risk, in addition to providing updated analyses on breast cancer risk in relation to birth weight, birth length and head circumference. Placental weight was not associated with risk for breast cancer in adulthood, but there was a positive association of breast cancer risk with birth length (HR 1.13, 95% CI 1.05-1.21, per 2 cm increment), though not with birth weight (HR 1.02, 95% CI 0.95-1.10 per 0.5 kg increment). For birth length, the graded increase in risk was particularly strong among women whose mothers were relatively tall (p for trend, 0.001), compared to the trend among women whose mothers were relatively short (p for trend, 0.221). The results showed a robust and positive association of birth length with breast cancer risk, and may be especially strong in women whose mothers were relatively tall. We found no association of placental weight with risk for breast cancer.

Proliferation of trophoblasts and Ki67 expression in preeclampsia

BACKGROUND/AIMS

Preeclampsia is a pregnancy-specific disease with the increased risk of maternal morbidity and mortality. It is characterised by placental vascular dysfunction. Despite the numerous studies on preeclampsia, studies evaluating proliferation of villous trophoblasts in preeclamptic placentas are limited. Ki67 is a proliferation marker that expresses in the nuclei of proliferating cells. In this study, we examined the proliferation of villous trophoblasts in placentas of preeclamptic patients by using Ki67 and compared it with placentas of normal pregnant patients.

MATERIAL AND METHODS

The current study is a prospective one, including 15 placentas from preeclamptic patients and 14 placentas from normal pregnancies as controls. For detection of proliferation in villous trophoblasts, Ki67 was used.

RESULTS

The Ki67 index was 11.48±1.67% in normal patients and 15.53±2.28% in preeclamptic patients. There was a difference in Ki67 index between the two groups (p < 0.001).

CONCLUSION

Our results support the opinion that trophoblasts undergo regeneration hyperplasia as a result of injuries arising on the villous surface in preeclampsia. Proliferation of trophoblasts may contribute the development of preeclampsia.

Preeclampsia does not alter vascular growth and expression of CD31 and vascular endothelial cadherin in human placentas

Preeclampsia is characterized by maternal endothelial dysfunction (e.g., increased maternal vascular permeability caused by the disassembly of endothelial junction proteins). However, it is unclear if preeclampsia is associated with impaired vascular growth and expression of endothelial junction proteins in human placentas. Herein, we examined vascular growth in placentas from women with normal term (NT) and preeclamptic (PE) pregnancies using two endothelial junction proteins as endothelial markers: CD31 and vascular endothelial-cadherin (VE-Cad). We also compared protein and mRNA expression of CD31 and VE-Cad between NT and PE placentas, and determined the alternatively spliced expression of CD31 using PCR. We found that CD31 and VE-Cad were immunolocalized predominantly in villous endothelial cells. However, capillary number density (total capillary number per unit villous area) and capillary area density (total capillary lumen area per unit villous area) as well as CD31 and VE-Cad protein and mRNA levels were similar between NT and PE placentas. PCR in combination with sequence analysis revealed a single, full-length CD31, suggesting that there are no alternatively spliced isoform of CD31 expressed in placentas. These data indicate that preeclampsia does not significantly affect vascular growth or the expression of endothelial junction proteins in human placentas.

Morphometric evaluation of preeclamptic placenta using light microscopic images

Deficient trophoblast invasion and anomalies in placental development generally lead to preeclampsia (PE) but the inter-relationship between placental function and morphology in PE still remains unknown. The aim of this study was to evaluate the morphometric features of placental villi and capillaries in preeclamptic and normal placentae. The study included light microscopic images of placental tissue sections of 40 preeclamptic and 35 normotensive pregnant women. Preprocessing and segmentation of these images were performed to characterize the villi and capillaries. Fisher's linear discriminant analysis (FLDA), hierarchical cluster analysis (HCA), and principal component analysis (PCA) were applied to identify the most significant placental (morphometric) features from microscopic images. A total of 10 morphometric features were extracted, of which the villous parameters were significantly altered in PE. FLDA identified 5 highly significant morphometric features (>90% overall discrimination accuracy). Two large subclusters were clearly visible in HCA based dendrogram. PCA returned three most significant principal components cumulatively explaining 98.4% of the total variance based on these 5 significant features. Hence, quantitative microscopic evaluation revealed that placental morphometry plays an important role in characterizing PE, where the villous is the major component that is affected.

Late-onset preeclampsia is associated with an imbalance of angiogenic and anti-angiogenic factors in patients with and without placental lesions consistent with maternal underperfusion

OBJECTIVE

An imbalance between maternal angiogenic/anti-angiogenic factors concentrations has been observed in preeclampsia (PE) and other obstetrical syndromes. However, the frequency of pathologic findings in the placenta and the changes in maternal plasma angiogenic/anti-angiogenic factor concentrations differ between late- and early-onset PE. The aim of this study was to determine if the maternal plasma concentrations of placental growth factor (PlGF), soluble endoglin (sEng), and soluble vascular endothelial growth factor receptor-1 and 2 (sVEGFR-1 and sVEGFR-2) are different in late-onset PE with and without placental pathologic findings consistent with maternal underperfusion.

STUDY DESIGN

A cross-sectional study was conducted including 64 uncomplicated women and 66 women with late-onset PE (>34 weeks) who had blood samples and placenta available for pathologic examination. Patients with late-onset PE were divided into those with and without placental histologic findings consistent with maternal underperfusion as proposed by the Society for Pediatric Pathology. Maternal plasma concentrations of PlGF, sEng, sVEGFR-1 and sVEGRF-2 were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

1) the prevalence of placental histological findings consistent with maternal underperfusion among women with late-onset PE was higher than that of those with an uncomplicated pregnancy (47% (31/66) vs. 7.8% (5/64), respectively; p < 0.01); 2) patients with late-onset PE and histological findings consistent with maternal underperfusion had a significantly lower median plasma concentration of PlGF, plasma PlGF/sVEGFR-1 ratio and plasma PlGF/sEng ratio than those with late-onset PE without placental underperfusion lesions (each p < 0.05); 3) the most common pathological findings in the placenta of patient with PE were lesions consistent with villous changes (77%, 24/31); and 4) isolated vascular lesions in the placenta were found only in 2 cases (6.5%), and the rest had a combination of villous and vascular lesions.

CONCLUSIONS

Nearly half of the patients with late-onset PE have placental lesions consistent with maternal underperfusion. These lesions are associated with an imbalance in the maternal concentration of angiogenic/anti-angiogenic factors. We propose that there is a link between maternal underperfusion and an anti-angiogenic state characterized by the changes in the concentrations of angiogenic and anti-angiogenic factors in women with late onset PE.

Trophoblast function in normal and preeclamptic pregnancy

Preeclampsia (PE) is a common disease of pregnancy that affects women particularly in their first pregnancies. Current estimates suggest that between 7 and 10% of pregnancies may be complicated by PE. Despite considerable research and medical efforts, the incidence of the disease has not changed substantially in the last century. In severe cases the disease may be life-threatening and is associated with high neonatal mortality and morbidity. Furthermore, therapy is often ineffective and at best treats the disease symptoms rather than the aetiology. One reason for the lack of progress may be that while the disease is generally agreed by most to be due to abnormal implantation and development of the placenta (events which happen in the first trimester) most research efforts have focused on managing and understanding the maternal disease. Since the disease typically appears in the last trimester, many weeks after the likely start of the pathology, it has been difficult to understand the progression of events. However, this picture has improved recently. The purpose here is to review how placental development is affected in PE and describe new insights into the causes. It is hoped that an understanding of the pathogenesis of the placental defects in PE will lead to new efforts towards early diagnosis, before the onset of clinical symptoms, as well as new treatments for these lesions.

Effects of a Streptococcus equi infection-mediated nutritional insult during mid-gestation in primiparous Thoroughbred fillies. Part 1: Placental and fetal development

REASONS FOR PERFORMING STUDY

There is a paucity of information on factors that influence placental development in the horse.

HYPOTHESIS

Changes in nutrition, particularly around the time of proliferative placental growth, can affect development of the placenta and fetal growth.

OBJECTIVE

To investigate the effects of 2 planes of nutrition and an unforeseen infection-mediated nutritional insult on placental and fetal development in the mare.

METHODS

Twenty maiden Thoroughbred fillies, age 3 or 4 years, mated to one Thoroughbred stallion, were maintained on either High or Moderate food intake throughout pregnancy. In mid-gestation all the mares unexpectedly became infected with Streptococcus equi and suffered varying degrees of weight loss as a consequence. Gross and stereological measurements of the placenta and measurements of foal birthweight, crown-rump length, ponderal index and plasma IGF-1 concentration were made at term.

RESULTS

Gains in bodyweight during gestation were significantly higher in the High vs. the Moderate nutrition groups. Placental and fetal growth parameters were not influenced by the plane of nutrition. However, transient weight loss in mid-gestation from acutely reduced food intake resulted in morphological changes to the allantochorion and decreased foal birthweight.

CONCLUSIONS

Excessive weight gain during gestation in maiden Thoroughbred fillies does not result in nutrient partitioning to the dam at the expense of the fetus. However, sudden weight loss in mid-gestation has detrimental effects on placental development which results in reduced fetal growth.

POTENTIAL RELEVANCE

Clinicians should appreciate the likely effects of maternal infection and resulting weight loss on pregnancy outcome.

A stereological perspective on placental morphology in normal and complicated pregnancies

Stereology applied to randomly-generated thin sections allows minimally-biased and economical quantitation of the 3D structure of the placenta from molecular to whole-organ levels. With these sampling and estimation tools, it is possible to derive global quantities (tissue volumes, interface surface areas, tubule lengths and particle numbers), average values (e.g. mean cell size or membrane thickness), spatial relationships (e.g. between compartments and immunoprobes) and functional potential (e.g. diffusive conductance). This review indicates ways in which stereology has been used to interpret the morphology of human and murine placentas including the processes of villous growth, trophoblast differentiation, vascular morphogenesis and diffusive transport. In human placenta, global quantities have shown that villous maturation involves differential growth of fetal capillaries and increases in endothelial cell number. Villous trophoblast is a continuously renewing epithelium and, through much of gestation, exhibits a steady state between increasing numbers of nuclei in cytotrophoblast (CT) and syncytiotrophoblast (ST). The epithelium gradually becomes thinner because its surface expands at a faster rate than its volume. These changes help to ensure that placental diffusing capacity matches the growth in fetal mass. Comparable events occur in the murine placenta. Some of these processes are perturbed in complicated pregnancies: 1) fetoplacental vascular growth is compromised in pregnancies accompanied by maternal asthma, 2) changes in trophoblast turnover occur in pre-eclampsia and intrauterine growth restriction, and 3) uteroplacental vascular development is impoverished, but diffusive transport increases, in pregnant mice exposed to particulate urban air pollution. Finally, quantitative immunoelectron microscopy now permits more rigorous analysis of the spatial distributions of interesting molecules between subcellular compartments or shifts in distributions following experimental manipulation.

Severe feto-placental abnormalities precede the onset of hypertension and proteinuria in a mouse model of preeclampsia

Preeclampsia is a prevalent and potentially devastating disorder of pregnancy. Characterized by a sudden spike in blood pressure and urinary protein levels, it is associated with significant obstetric complications. BPH/5 is an inbred mouse model of preeclampsia with borderline hypertension before pregnancy. BPH/5 mice develop hypertension, proteinuria, and endothelial dysfunction during late gestation (after E14.5). We hypothesized that BPH/5 mice might exhibit early feto-placental abnormalities before the onset of maternal disease. All placental cell lineages were present in BPH/5 mice. However, the fetal and placental weights were reduced, with abnormalities in all the placental zones observed starting early in gestation (E9.5-E12.5). The fractional area occupied by the junctional zone was significantly reduced at all gestational timepoints. Markedly fewer CDKN1C-stained trophoblasts were seen invading the proximal decidual zone, and this was accompanied by reductions in Cdkn1c gene expression. Trophoblast giant cell morphology and cytokeratin staining were not altered, although the mRNA levels of several giant cell-specific markers were significantly downregulated. The labyrinth layer displayed decreased branching morphogenesis of endothelial cells, with electron microscopy evidence of attenuated trophoblast layers. The maternal decidual arteries showed increased wall-to-lumen ratios with persistence of actin-positive smooth muscle cells. These changes translated into dramatically increased vascular resistance in the uterine arteries, as measured by pulse-wave Doppler. Collectively, these results support the hypothesis that defects at the maternal-fetal interface are primary causal events in preeclampsia, and further suggest the BPH/5 model is important for investigations of the underlying pathogenic mechanisms in preeclampsia.

Pre-eclampsia and Fetal Growth Restriction: How Morphometrically Different is the Placenta?

Both pre-eclampsia (PET) and fetal growth restriction (FGR) pose a heavy burden on fetal and maternal health and may disrupt pregnancy outcome. Using design based stereological techniques, placental vascular and villous morphology were assessed to determine the individual role played by both PET and FGR on placental growth during the third trimester. The following placentas delivered between 25 and 41 weeks of gestation were included into the study; controls (n=16), PET (n=20), FGR (n=17) and PET-FGR (n=16). Each placenta was uniformly randomly sampled and the sampled tissue processed to paraffin. Sections were stained with a CD34 antibody and the following morphometric parameters estimated: volumes, surface areas, length, diameters and the shape factor of the villous (terminal and intermediate) and vascular placental features. For stereologically estimated parameters pure PET had an effect on IVS and terminal villi volume only. FGR alone or when coexisting with PET contributed towards significant reductions in volumetric and surface area terminal villous and vascular features. FGR factors also contributed towards a significant reduction in the lengths of all parameters estimated and in the terminal villi diameter. Additionally, FGR was associated with a significant difference in shape factor indices for both intermediate and terminal villi. This study has shown that PET on its own has limited influence on the placental morphology studied, since the vascular features estimated do not differ stereologically from age matched normal controls. However, placental morphology is different between PET and PET-FGR and between PET-FGR and FGR. PET and FGR may have a cumulative effect on placental villous and vascular morphology as seen in the PET-FGR but there is no synergistic effect. These morphological abnormalities may have major physiological implications in terms of placental function and fetal growth.

The placenta in pre-eclampsia and intrauterine growth restriction: studies on exchange surface areas, diffusion distances and villous membrane diffusive conductances

We test the null hypothesis that the morphometric diffusive conductance of the placental villous membrane does not alter in pregnancies complicated by intrauterine growth restriction (IUGR) or pre-eclampsia (PE). Placentas were collected from cases of normotensive IUGR, pure PE, PE+IUGR and from control pregnancies. Microscopical fields on formalin-fixed, trichrome-stained histological sections were randomly sampled for location and orientation. Using stereological methods, the exchange surface areas of peripheral (terminal and intermediate) villi and their fetal capillaries and the arithmetic and harmonic mean thicknesses of the villous membrane (maternal aspect of trophoblast to luminal aspect of vascular endothelium) were estimated. An index of the variability in thickness of this membrane, and an estimate of its oxygen diffusive conductance, was derived secondarily. Group comparisons were drawn using two-way analysis of variance to identify main effects (of PE or IUGR) and interaction effects (between PE and IUGR). PE did not have significant effects on placental morphology and there were no significant effects of PE or IUGR on membrane thickness or its variability. In contrast, IUGR (with or without PE) was associated with reduced surface areas and this was the principal factor leading to a smaller membrane diffusive conductance in these placentas. When account was taken of fetal mass, specific conductance showed no effects of PE or IUGR despite the mass-specific conductance in pure IUGR placentas appearing to be smaller than that in controls. The decline in total conductances is indicative of perturbations operating at the levels of villous trophoblast and fetal vasculature and these may contribute to fetal hypoxic stress.

Maternal medicine: Morphometric placental villous and vascular abnormalities in early- and late-onset pre-eclampsia with and without fetal growth restriction

OBJECTIVE

To evaluate placental morphology in pregnancies complicated by early- and late-onset pre-eclampsia (PET) with and without fetal growth restriction (FGR) using stereological techniques.

DESIGN

A total of 69 pregnant women were studied. Twenty women had pregnancies complicated by PET, 17 by FGR and 16 by both PET and FUR; the remaining 16 were from gestational-age-matched controls. Each group was further classified into early onset (<34 weeks) and late onsets (>34 weeks) based on gestational ages.

SETTING

NPIMR at Northwick Park and St Marks Hospital.

POPULATION

placentae from pregnant women.

METHODS

Formalin-fixed, wax-embedded sections stained with anti-CD34 antibodies and counterstained with haematoxylin.

MAIN OUTCOME MEASURES

Volumes, surface areas, lengths, diameters and shape factors of the villous tissues and fetal vasculature in the intermediate and terminal villi of all the groups studied.

RESULTS

Terminal villi volume and surface area were compromised in early-onset PET cases, late-onset PET had no impact on peripheral villi or vasculature features. The morphology of the vascular and villous subcomponents in the intermediate and terminal villi was significantly influenced by late-onset FGR, whereas early-onset FGR caused a reduction in placental weight. Length estimates were not influenced by PET, FGR or age of onset. Intermediate arteriole shape factor was significantly reduced in late-onset FGR.

CONCLUSIONS

Isolated early-onset PET was associated with abnormal placental morphology, but placentas from late-onset PET were morphologically similar to placentas from gestational-age-matched controls, confirming the existence of two subsets of this condition and supporting the hypothesis that late-onset PET is a maternal disorder and not a placental disease.

Placental function in development and disease

The placenta is an organ that clinicians and embryologists would all agree is important for pregnancy success. Unfortunately, however, they too often ignore it when they are exploring causes for embryonic, fetal and perinatal complications. The core function of the placenta is to mediate the transport of nutrients between the maternal and fetal circulation, but it also has critical endocrine functions that alter different maternal physiological systems in order to sustain pregnancy. Both its development and ongoing functions can be dynamically regulated by environmental factors, including nutrient status and tissue oxygenation. In recent years, mainstream attention has begun to shift onto the placenta and it is now becoming clear that placental pathology is associated with several complications in human and animal pregnancies, including embryonic lethality, fetal growth restriction, pre-eclampsia and the high rates of fetal deaths observed after nuclear transfer (cloning).

Mechanisms of Disease: pre-eclampsia

Pre-eclampsia, a syndrome of pregnant women, is one of the leading causes of maternal and fetal morbidity and mortality. Despite active research, the etiology of this disorder remains an enigma. Recent work has, however, provided promising explanations for the causation of the disorder and some of its phenotypes. Evidence indicates that the symptoms of hypertension and proteinuria, upon which the diagnosis of pre-eclampsia is based, have several underlying causes. Nevertheless, the treatment of pre-eclampsia has not changed significantly in over 50 years. This review describes the most recent insights into the pathophysiology of pre-eclampsia from both basic and clinical research, and attempts to provide a unifying hypothesis to reconcile the abnormalities at the feto-placental level and the clinical features of the maternal syndrome. The novel findings outlined in this review provide a rationale for potential future prophylactic and therapeutic interventions for pre-eclampsia.

Histomorphometric study of placental villi vascular volume in toxemia and diabetes

The quantitative changes in the vascular tree in placentas from pregnancies complicated by diabetes mellitus and preeclampsia (PE) are not well defined. The purpose of this study was to quantify placental villi cross-sectional area of capillaries assessed by a computerized morphometry system in pregnancies complicated by PE (n = 23), well-controlled pregestational diabetes mellitus (PGDM; n = 10), and healthy controls (n = 13). Our aims were to test whether villous capillarization volume was changed in PE without intrauterine growth restriction or PGDM compared with the control group and to study these effects in 3 different areas of the placenta. Examination of placentas in women with PGDM and PE revealed limited pathological changes on light microscopic examination. However, the morphometric analysis revealed a more than 5-fold decrease of villous vascular volume in PGDM compared with controls (P = .003) and a 1.6-fold decrease in the PE group that did not reach statistical significance. These findings show quantitative changes in the villous vascular tree in PGDM that are not detectable by conventional light microscopy and suggest that morphometric analysis of the capillary tree may have diagnostic importance in this entity. The findings differ significantly from those previously reported in pregestational diabetes and do not differ significantly from those reported in PE without intrauterine growth restriction.

Recurrence of pre-eclampsia across generations: exploring fetal and maternal genetic components in a population based cohort

OBJECTIVES

To assess the impact on risk of pre-eclampsia of genes that work through the mother, and genes of paternal origin that work through the fetus.

DESIGN

Population based cohort study.

SETTING

Registry data from Norway.

PARTICIPANTS

Linked generational data from the medical birth registry of Norway (1967-2003): 438,597 mother-offspring units and 286,945 father-offspring units.

MAIN OUTCOME MEASURES

Pre-eclampsia in the second generation.

RESULTS

The daughters of women who had pre-eclampsia during pregnancy had more than twice the risk of pre-eclampsia themselves (odds ratio 2.2, 95% confidence interval 2.0 to 2.4) compared with other women. Men born after a pregnancy complicated by pre-eclampsia had a moderately increased risk of fathering a pre-eclamptic pregnancy (1.5, 1.3 to 1.7). Sisters of affected men or women, who were themselves born after pregnancies not complicated by pre-eclampsia, also had an increased risk (2.0, 1.7 to 2.3). Women and men born after pre-eclamptic pregnancies were more likely to trigger severe pre-eclampsia in their own (or their partner's) pregnancy (3.0, 2.4 to 3.7, for mothers and 1.9, 1.4 to 2.5, for fathers).

CONCLUSIONS

Maternal genes and fetal genes from either the mother or father may trigger pre-eclampsia. The maternal association is stronger than the fetal association. The familial association predicts more severe pre-eclampsia.

Term preeclampsia is associated with minimal histopathological placental features regardless of clinical severity

Preeclampsia (PET) is a serious complication of pregnancy, which is associated with uteroplacental disease and reduced uteroplacental perfusion. One of the histological features in placentas from pregnancies complicated by PET is infarction, representing focal severe uteroplacental ischaemia. This study examines the relationship between gestation at induced delivery and the prevalence of placental infarction using a placental pathology database to identify induced or operative deliveries on the basis of severe PET. The clinical and pathological findings were reviewed. Thirty-seven cases were identified, (4.9% of all placentas submitted). In 16 (43%), non-peripheral significant infarcts were identified histologically, including 13/20 (65%) requiring delivery before 34 weeks' compared to 3/17 (17%) requiring delivery > or = 34 weeks (z=2.9, P<0.01). Histological infarction is common in placentas from pregnancies complicated by severe PET but the prevalence is significantly greater in cases requiring delivery at earlier gestations, even when similar clinical indications for delivery are applied.

An image analysis technique for the investigation of variations in placental morphology in pregnancies complicated by preeclampsia with and without intrauterine growth restriction

OBJECTIVE

The purpose of this study was to use visual image analysis to observe changes in the morphology and composition of placental villi in pregnancies complicated by preeclampsia (PE) and intrauterine growth restriction (IUGR).

METHODS

Placental biopsies from nine normal pregnancies, five cases of PE, five cases of IUGR, and five cases of PE with IUGR (PE x IUGR) were randomly sampled. Formalin-fixed, wax-embedded sections were stained with hematoxylin and eosin (H&E) and subjected to image analysis. The placental areas occupied by villi, syncytiotrophoblast, and syncytial cytoplasm and nuclei were quantified.

RESULTS

Significantly smaller placentas were obtained from growth-restricted pregnancies. PE, with and without IUGR, had no effect on the total area occupied by villi or intervillous space. IUGR alone showed a real and consistent reduction in villous area (56.0 +/- 2.4% vs 43.6 +/- 3.3%, P <.03). While the ratio of syncytial to villous areas were noticeably reduced in all cases of PE (0.38 +/- 0.03 vs 0.24 +/- 0.07, P <.05), this ratio remained unchanging in IUGR. Birth weight was positively correlated to both placental size and total villous area occupied. Moreover, increasingly positive relationships were recorded between both syncytiotrophoblast area and syncytiotrophoblast cytoplasm and birth weight (P <.01 and P <.001, respectively).

CONCLUSION

These measurements point to impoverished villus development in idiopathic IUGR. The observed changes in PE with IUGR were more akin to PE without growth restriction than IUGR alone. This suggests that idiopathic IUGR and IUGR in PE have a separate etiology, idiopathic IUGR arising through a reduction in villous area alone, and IUGR in PE caused by changes in syncytiotrophoblast quantity, more specifically the amount of syncytiotrophoblast cytoplasm.

Aspects of human fetoplacental vasculogenesis and angiogenesis. III. Changes in complicated pregnancies

Patterns of fetoplacental angiogenesis vary not only during the course of a normal pregnancy but also in certain pregnancy pathologies. Here, we review some of the molecular and morphological events which occur in complicated pregnancies. The pregnancy complications are chosen in an attempt to represent the possible different origins (preplacental, uteroplacental, postplacental) of fetal hypoxia. Molecular events focus on reported changes in hypoxia-inducible factors, angiopoietins and the vascular endothelial, basic fibroblast and placenta growth factors and their receptors. Morphological changes focus on patterns of angiogenesis (branching and non-branching) and a consistent set of morphometric descriptors (covering measures of total capillary growth, villous capillarization and capillary size and shape in transverse section). Apart from some uncertainties due to lack of information, or failure to resolve fully the effects of intrauterine growth restriction and pre-eclampsia, alterations in the angiogenic growth factors and morphologies of capillaries and villi in different complicated pregnancies seem to conform reasonably well to those predicted by the fetal hypoxia paradigm. However, it is clear that future studies on the effects of different origins of fetal hypoxia should exercise more care in the choice and interpretation of relevant descriptors and take more account of the parallel effects of possible confounders. In addition, rather than comparing uncomplicated and complicated pregnancies only at term, more information about molecular and morphological events that occur throughout gestation would be extremely valuable. This includes further studies on changes in growth factor receptors, the less-well-documented angiogenic factors (e.g. angiogenin, angiostatin, endostatin) and the associations between endothelial cells and pericytes. A more integrated approach involving also parallel analysis of the effects of erythropoietin and other potential vasoactive factors on the behaviour and morphology of fetal vessels would be beneficial.

Is pre-eclampsia more than one disease?

OBJECTIVES

The clinical characteristics of pre-eclampsia (gestational hypertension and proteinuria) may represent separate pathogenetic conditions. Pre-eclampsia accompanied by restricted fetal growth may originate from abnormal implantation, and appropriate or high birthweights may indicate a mixture of conditions, ranging from mild pre-eclampsia with modest placental involvement to hypertensive conditions without placental disease.

DESIGN

Prospective, observational study.

SETTING

General population.

POPULATION

We used data from the Medical Birth Registry of Norway, a population-based registry that has recorded births since 1967. For this study, we used information on length of gestation and presence of pre-eclampsia among 1,679,205 singletons born between 1967 and 1998. Pre-eclampsia was diagnosed in 44,220 (2.6%) pregnancies.

METHODS

We studied the risk of pre-eclampsia in relation to standardised measures (z scores) of birthweight, adjusted for length of gestation, and stratified by term and preterm delivery. We also explored whether gestational diabetes was more prevalent in conjunction with preterm than term pre-eclampsia.

MAIN OUTCOME MEASURES

Pre-eclampsia diagnosed at term or preterm.

RESULTS

For pre-eclampsia diagnosed around term, there was a U-shaped association with birthweight. Compared with appropriate birthweights for gestation, the risk of term pre-eclampsia was more than fourfold higher (relative risk [RR] 4.5, 95% confidence interval [CI], 4.3 to 4.7) if the baby's birthweight was lower than two standard deviations under the mean. For birthweights three standard deviations or higher than the mean, pre-eclampsia was more than twice as likely (RR 2.6, 95% CI 2.2-2.9). In contrast, the risk of preterm pre-eclampsia displayed an L-shaped association with birthweight. Low birthweight (less than -2 standard deviations) was associated with greatly increased risk (RR 9.9, 95% CI 9.1-10.9), but for high birthweights (>or=3 standard deviations), there was no association with the risk of preterm pre-eclampsia (RR 1.2, 95% CI 0.7-2.1). The prevalence of gestational diabetes was three times (prevalence ratio 3.3, 95% CI 2.6-3.6) higher in preterm than term pre-eclampsia.

CONCLUSION

Whereas pre-eclampsia with preterm delivery associated with low birthweight may be caused by underlying placental abnormality, pre-eclampsia delivered at term may represent a mixture of conditions, ranging from mild pre-eclampsia with moderate placental affection to hypertensive conditions in pregnancy without placental dysfunction.

The frequency and severity of placental findings in women with preeclampsia are gestational age dependent

OBJECTIVE

The purpose of this study was to evaluate placental lesions found in women with preeclampsia compared with normotensive control subjects and to determine whether the presence of these lesions are related to gestational age at delivery.

STUDY DESIGN

Placental disease of women with preeclampsia at 24 to 42 weeks of gestation was compared with the placental disease of normotensive gestational age-matched control subjects. The placental lesions that were studied specifically included decidual arteriolopathy, thrombi in the fetal circulation, central infarction, intervillous thrombi, and hypermaturity of villi. Data analysis involved the chi(2) test, the Student t test, and logistic regression; odds ratios and CIs were estimated.

RESULTS

Placentas from women with preeclampsia (n=158) and normotensive control subjects (n=156) were evaluated. Among women with preeclampsia, 67% had severe disease. Placental lesions were studied according to gestational age at delivery: <28, 28 to 32, 33 to 36, and >or=37 weeks of gestation. Of the placental lesions that were studied, decidual arteriolopathy (odds ratio, 23.8, 95% CI 10.0-57.0), hypermaturity of villi (odds ratio, 12.4; 95% CI 5.3-29.2), intervillous thrombi (odds ratio, 1.95;95% CI 1.0-3.7), central infarction (odds ratio, 5.9; 95% CI 3.1-11.1), and thrombi in the fetal circulation (odds ratio, 2.8; 95% CI 1.2-6.6) were found to have significantly higher rates in the preeclamptic group. In contrast, the rate of chorioamnionitis was significantly lower in the preeclamptic group (odds ratio, 0.2; 95% CI 0.1-0.4). The rates of abruptio placentae and meconium staining were not different between the two groups. Within the preeclamptic group, the rates of decidual arteriolopathy (P<.0001), central infarction (P=.0001), and hypermaturity of villi (P<.0001) were higher the earlier the gestational age at delivery.

CONCLUSION

Placentas in women with preeclampsia have increased amounts of disease. The rate is increased with lower gestational ages at the time of delivery for women with preeclampsia.

The genetics of pre-eclampsia: a feto-placental or maternal problem?

Pre-eclampsia is a potentially life-threatening disease of women during pregnancy leading to hypertension and proteinuria. It affects 1 in 15 pregnancies but, despite intense research efforts, the cause of the disease remains mysterious. Because pre-eclampsia only occurs during pregnancy and its symptoms resolve after delivery, factors from the placenta are thought to be involved. The role of the placenta could be production of 'abnormal' factors that initiate widespread inflammation and vaso-constriction. Alternatively, because the placenta normally contributes to maternal cardiovascular adaptations of pregnancy, it may be that normal placental functions fail in pre-eclampsia or that susceptibilities in the mother to hypertensive, vascular and/or renal disease prevent the appropriate normal responses to them. The potential contributions of both maternal and fetal genes to the onset of the disease have complicated the genetic analysis of the disease in humans. Recent studies have identified strains of transgenic and mutant mice that develop the hallmark features of pre-eclampsia-like disease - gestational hypertension, proteinuria and kidney lesions (glomerulosclerosis). Comparison of three different mouse models suggests that pre-eclampsia can be initiated by at least three independent mechanisms: pre-existing borderline maternal hypertension that is exacerbated by pregnancy (BPH/5 strain of mice), elevated levels of the vasoconstrictor angiotensin II in the maternal circulation by placental over-production of renin (renin/angiotensinogen transgenic mice), and placental pathology (p57Kip2 mutant mice). These findings imply that the pathogenesis of pre-eclampsia cannot be explained by a single mechanism. Therefore, segregation of the human disease into different subtypes may be a key first step in identifying genetic risk factors.

Stereological investigation of placental morphology in pregnancies complicated by pre-eclampsia with and without intrauterine growth restriction

The aim of this study was to quantify placental morphology in pregnancies complicated by pre-eclampsia with and without intrauterine growth restriction. Particular attention is given to the dimensions and composition of peripheral (intermediate+terminal) villi. Placentae from 9 control pregnancies, 5 cases of pre-eclampsia, 5 cases of intrauterine growth restriction and 5 cases of pre-eclampsia with intrauterine growth restriction were randomly sampled for location and position. Formalin-fixed, wax-embedded sections stained by the Masson trichrome method were subjected to stereological analysis in order to quantify the volumes of placental components and the surfaces and derived diameters for peripheral villi and fetal capillaries. Group comparisons were drawn using two-way analysis of variance. Fetal weights were reduced in all complicated pregnancies but only intrauterine growth restriction was accompanied by a significantly smaller placenta. Pre-eclampsia was not associated with main effects on placental morphology and (except for trophoblast thickness) there were no interaction effects involving pre-eclampsia. In contrast, intrauterine growth restriction was associated with a placenta which had reduced volumes of intervillous space and all types of villi (stem, intermediate, terminal). The impoverished growth of peripheral villi affected all tissues (trophoblast, stroma, capillaries) and was accompanied by smaller exchange surface areas and a thicker trophoblastic epithelium. The derived mean diameters of villi and capillaries were not affected. It is concluded that intrauterine growth restriction, but not pre-eclampsia, is associated with substantial changes in placental morphology including impoverished growth of villi and fetal vasculature. These changes are likely to reduce placental oxygen diffusive conductances and contribute to fetal hypoxic stress.

Fetal magnetoencephalography in intrauterine growth retarded pregnancies

OBJECTIVE

To investigate the fetal brain activity in pre-eclamptic and normal pregnancies. Biomagnetic measurements were performed by means of a superconducting quantum interference device (SQUID) in an electrically shielded room of low magnetic noise.

METHODS

The study population included 28 pre-eclamptic (34-37 weeks' gestation) and 19 normal pregnancies (34-37 weeks' gestation). The pre-eclamptic group consisted of 11 cases with birth weight below the 10th percentile (1969 +/- 129 g) and 17 cases above the 10th percentile (2496 +/- 257 g). Biomagnetic signals (waveforms) recorded from fetal brains were expressed in terms of magnetic power spectral amplitudes.

RESULTS

The total corresponding spectral amplitudes in the frequency range 2-7 Hz were high (719 +/- 69 Ft/ radical Hz in neonates <10th percentile and 537 +/- 105 Ft/ radical Hz in neonates >10th percentile) in most (82%) pre-eclamptic pregnancies and low (382 +/- 35 Ft/ radical Hz) in most normal pregnancies (95%). The difference between normal and all pre-eclamptic pregnancies was highly significant (Student's t-test: p < 0.0001). Comparing the two groups of pre-eclampsia we found also a highly significant difference (Student's t-test: p < 0.0001).

CONCLUSION

Biomagnetic measurements of fetal brain activity could be useful in the assessment of fetal central nervous system development.

Mid-trimester triple test levels in early and late onset severe pre-eclampsia

OBJECTIVE

To study whether the degree of elevation of mid-trimester triple test markers differs in patients with early versus late onset severe pre-eclampsia.

METHODS

A retrospective study of the medical records of 102 patients with severe pre-eclampsia for whom mid-trimester triple test result data were available was made. None of these patients had fetuses with abnormal karyotype nor delivered infants with malformations. Pre-eclampsia was defined as early onset when it presented before 32 weeks' gestation. The levels of mid-trimester maternal serum alpha-fetoprotein (MSAFP), human chorionic gonadotrophin (hCG) and unconjugated oestriol (MSuE(3)) in patients with early and late onset severe pre-eclampsia were compared.

RESULTS

Twenty-five patients had early onset and 77 patients had late onset severe pre-eclampsia. The two groups did not differ significantly with regard to age, weight, parity and severity of pre-eclampsia. The mean MSAFP in patients with early onset was significantly higher than in patients with late onset severe pre-eclampsia (1.46 MoM, SE 0.12 versus 1.16 MoM, SE 0.05; p=0.01). The mean hCG in the early onset group was also significantly higher than in the late onset group (1.71 MoM, SE 0.18 versus 1.21 MoM, SE 0.07; p=0.03). Mean MSuE(3) levels in patients with early onset were significantly lower than in patients with late onset severe pre-eclampsia (0.83 MoM, SE 0.05 versus 1.02 MoM, SE 0.03; p=0.04).

CONCLUSIONS

Higher MSAFP and hCG, and lower MSuE(3), may be more significant markers of early rather than late onset severe pre-eclampsia.

A stereological method for testing whether or not there is random deposition of perivillous fibrin-type fibrinoid at the villous surface: description and pilot applications to term placentae

We present a stereological method for testing whether or not there is random deposition of fibrin-type fibrinoid (FTF) at the villous surface of human placenta. The method requires random sampling of tissue with test lattice lines superimposed on microscopic fields at random positions and orientations. Test lines are used to generate chance intersections with specified sub-domains of the villous surface. At least three sub-domains are distinguishable: non-syncytial knots (nonSK), syncytial knots (SK) and areas of trophoblast de-epithelialization (DEP). Other sub-domains may be included to suit individual circumstances and project aims. The relative numbers of intersections with sub-domains provide the basis for an 'expected' distribution. Subsequently, this is compared with an 'observed' distribution which can be calculated from empirical estimates of the numbers of intersections with sub-domains associated with perivillous FTF (e.g. nonSK+FTF, SK+FTF and DEP+FTF). Expected and observed distributions can be compared by a chi-squared analysis. If the null hypothesis (no difference) is rejected, chi-squared values for individual sub-domains can be analysed in order to localize and interpret sites of preferential deposition. Comparisons may be drawn for individual placentae as well as a group of placentae, thereby permitting assessment of inter-placental variability. Finally, between-group comparisons may be drawn in order to test whether or not FTF deposition patterns differ in control and other pregnancies. Worked examples of the statistical procedures are provided. Preliminary results of applications to placentae from normal and complicated (hypobaric hypoxia) pregnancies are presented. They show that FTF deposition is non-random and preferentially located at sites of de-epithelialization. De-epithelialization may be a consequence of syncytial degeneration but also, at least in part, of continuous trophoblast turnover in which syncytial fragments rich in (pre-) apoptotic nuclei detach from the epithelium and are deported from the maternal intervillous space. The nascent detachment site is immediately covered by FTF prior to repair by re-epithelialization.

Placental insights into neurodevelopmental and other childhood diseases

Deficient information regarding placental pathology has compromised epidemiological investigations of cerebral palsy, mental retardation, and other diseases. This article reviews light microscopic signs of low placental blood flow, fetal nucleated red blood cells, villitis (villous inflammatory lesions), chorangiosis (placental villous capillary hypervascularity), meconium staining, and chorioamnionitis. These findings can be used with data of birth weight, head circumference, and length to document the duration of fetal disease. The article includes pathophysiological considerations; for example, chorioamnionitis and fetal meconium discharge may cause autacoids to produce fetal hypoperfusion of the fetal brain and other vital organs.

Proliferation of villous trophoblast of the human placenta in normal and abnormal pregnancies

The proliferation of villous trophoblast in the human placenta was estimated throughout normal gestation and in term placentae from preeclamptic and smoking mothers by two different methods. These were: 1) labeling of DNA producing cells by bromodeoxyuridine (BrdU) followed by immunohistochemistry using a monoclonal anti-BrdU antibody, and 2) immunohistochemical identification of all proliferating cells by the monoclonal antibody Ki67. Both methods revealed comparable results. In uncomplicated pregnancies there was a remarkable decrease in the labeling indices from early gestation to term. This was the result of a diminution of the number of Langhans' cells, although the cell division rate within the Langhans' cell layer remained nearly constant throughout gestation. A prolongation of the cell cycle in the cytotrophoblast cells at term was indicated by an increase in the Ki67/BrdU ratio. Compared with normal term placentae, there was an increase in the trophoblast proliferation rate in preeclampsia, but not in placentae from smoking mothers. Moreover, the number of Langhans' cells was diminished in placentae from smokers. The results indicate that there are different pathogenetic mechanisms of placental impairment in preeclampsia and in maternal smoking. In preeclampsia an injury to the syncytiotrophoblast seems to lead to a repair hyperplasia of the cytotrophoblast, whereas in maternal smoking, there seems to be a direct toxic effect on the cytotrophoblastic cells.