Fetoplacental vascular alterations associated with fetal growth restriction

Maternal serum PlGF associates with 3D power doppler ultrasound markers of utero-placental vascular development in the first trimester: the rotterdam periconception cohort

OBJECTIVE (S)

Circulating angiogenic factors are used for prediction of placenta-related complications, but their associations with first-trimester placental development is unknown. This study investigates associations between maternal angiogenic factors and utero-placental vascular volume (uPVV) and utero-placental vascular skeleton (uPVS) as novel imaging markers of volumetric and morphologic (branching) development of the first-trimester utero-placental vasculature.

METHODS

In 185 ongoing pregnancies from the VIRTUAL Placenta study, a subcohort of the ongoing prospective Rotterdam Periconception cohort, three-dimensional power Doppler ultrasounds of the placenta were obtained at 7-9-11 weeks gestational age (GA). The uPVV was measured as a parameter of volumetric development and reported the vascular quantity in cm3. The uPVS was generated as a parameter of morphologic (branching) development and reported the number of end-, bifurcation- crossing- or vessel points and total vascular length. At 11 weeks GA, maternal serum biomarkers suggested to reflect placental (vascular) development were assessed: placental growth factor (PlGF), soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng). sFlt-1/PlGF and sEng/PlGF ratios were calculated. Multivariable linear regression with adjustments was used to estimate associations between serum biomarkers and uPVV and uPVS trajectories.

RESULTS

Serum PlGF was positively associated with uPVV and uPVS development (uPVV: β = 0.39, 95% CI = 0.15;0.64; bifurcation points: β = 4.64, 95% CI = 0.04;9.25; crossing points: β = 4.01, 95% CI = 0.65;7.37; total vascular length: β = 13.33, 95% CI = 3.09;23.58, all p-values < 0.05). sEng/PlGF ratio was negatively associated with uPVV and uPVS development. We observed no associations between sFlt-1, sEng or sFlt-1/PlGF ratio and uPVV and uPVS development.

CONCLUSION(S)

Higher first-trimester maternal serum PlGF concentration is associated with increased first-trimester utero-placental vascular development as reflected by uPVV and uPVS. Clinical trial registration number Dutch Trial Register NTR6854.

Molecular regulators of defective placental and cardiovascular development in fetal growth restriction

Placental insufficiency is one of the major causes of fetal growth restriction (FGR), a significant pregnancy disorder in which the fetus fails to achieve its full growth potential in utero. As well as the acute consequences of being born too small, affected offspring are at increased risk of cardiovascular disease, diabetes and other chronic diseases in later life. The placenta and heart develop concurrently, therefore placental maldevelopment and function in FGR may have profound effect on the growth and differentiation of many organ systems, including the heart. Hence, understanding the key molecular players that are synergistically linked in the development of the placenta and heart is critical. This review highlights the key growth factors, angiogenic molecules and transcription factors that are common causes of defective placental and cardiovascular development.

Comparison of 2D and 3D oxygen-enhanced MRI of the placenta

Oxygen-Enhanced Magnetic Resonance Imaging (OE-MRI) of the human placenta is potentially a sensitive marker of in vivo oxygenation. This methodological study shows that full coverage of the placenta is possible using 3D mapping of the change in longitudinal relaxation rate (ΔR1), in a group of healthy pregnant subjects breathing elevated levels of oxygen. Twelve pregnant subjects underwent a comparison of 2D and 3D OE-MRI. ΔR1 was mapped for a single 2D slice (ss-2D), a single matched-slice from the 3D volume (ss-3D) and the full 3D volume (vol-3D). The group-average median ΔR1 values for ss-3D (0.023 s-1) and vol-3D (0.022 s-1) do not differ significantly from ss-2D (0.020 s-1), when compared using a two-tailed paired t-test (ss-3D (p = 0.58) and vol-3D (p = 0.70)). However, median baseline T1 (T1b) for ss-2D was higher (1603 ms) than T1b for ss-3D (1540 ms, p = 0.07) and significantly higher than vol-3D (1515 ms, p = 0.02), when compared using a two-tailed paired t-test. In contrast with previous studies, no correlation of median ΔR1 with gestation age at scan for the normal group (N = 10) was observed for ss-2D, likely due to the smaller gestational range. Full volume OE-MRI maps reveal sensitivity to changes in ΔR1, with some participants showing an enhanced gradient in the intermediate space between the fetal and maternal sides of the placenta in the 3D data. This study shows that it is feasible to acquire whole placental volume OE-MRI data in women with healthy pregnancy.

Placental Drug Delivery to Treat Pre-Eclampsia and Fetal Growth Restriction

Pre-eclampsia and fetal growth restriction (FGR) continue to cause unacceptably high levels of morbidity and mortality, despite significant pharmaceutical and technological advances in other disease areas. The recent pandemic has also impacted obstetric care, as COVID-19 infection increases the risk of poor pregnancy outcomes. This review explores the reasons why it lacks effective drug treatments for the placental dysfunction that underlies many common obstetric conditions and describes how nanomedicines and targeted drug delivery approaches may provide the solution to the current drug drought. The ever-increasing range of biocompatible nanoparticle formulations available is now making it possible to selectively deliver drugs to uterine and placental tissues and dramatically limit fetal drug transfer. Formulations that are refractory to placental uptake offer the possibility of retaining drugs within the maternal circulation, allowing pregnant individuals to take medicines previously considered too harmful to the developing baby. Liposomes, ionizable lipid nanoparticles, polymeric nanoparticles, and adenoviral vectors have all been used to create efficacious drug delivery systems for use in pregnancy, although each approach offers distinct advantages and limitations. It is imperative that recent advances continue to be built upon and that there is an overdue investment of intellectual and financial capital in this field.

Morphologic development of the first-trimester utero-placental vasculature is positively associated with embryonic and fetal growth: the Rotterdam Periconception Cohort

STUDY QUESTION

Is morphologic development of the first-trimester utero-placental vasculature associated with embryonic growth and development, fetal growth, and birth weight percentiles?

SUMMARY ANSWER

Using the utero-placental vascular skeleton (uPVS) as a new imaging marker, this study reveals morphologic development of the first-trimester utero-placental vasculature is positively associated with embryonic growth and development, fetal growth, and birth weight percentiles.

WHAT IS KNOWN ALREADY

First-trimester development of the utero-placental vasculature is associated with placental function, which subsequently impacts embryonic and fetal ability to reach their full growth potential. The attribution of morphologic variations in the utero-placental vascular development, including the vascular structure and branching density, on prenatal growth remains unknown.

STUDY DESIGN, SIZE, DURATION

This study was conducted in the VIRTUAL Placental study, a subcohort of 214 ongoing pregnancies, embedded in the prospective observational Rotterdam Periconception Cohort (Predict study). Women were included before 10 weeks gestational age (GA) at a tertiary referral hospital in The Netherlands between January 2017 and March 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We obtained three-dimensional power Doppler volumes of the gestational sac including the embryo and the placenta at 7, 9, and 11 weeks of gestation. Virtual Reality-based segmentation and a recently developed skeletonization algorithm were applied to the power Doppler volumes to generate the uPVS and to measure utero-placental vascular volume (uPVV). Absolute vascular morphology was quantified by assigning a morphologic characteristic to each voxel in the uPVS (i.e. end-, bifurcation-crossing-, or vessel point). Additionally, total vascular length (mm) was calculated. The ratios of the uPVS characteristics to the uPVV were calculated to determine the density of vascular branching. Embryonic growth was estimated by crown-rump length and embryonic volume. Embryonic development was estimated by Carnegie stages. Fetal growth was measured by estimated fetal weight in the second and third trimester and birth weight percentiles. Linear mixed models were used to estimate trajectories of longitudinal measurements. Linear regression analysis with adjustments for confounders was used to evaluate associations between trajectories of the uPVS and prenatal growth. Groups were stratified for conception method (natural/IVF-ICSI conceptions), fetal sex (male/female), and the occurrence of placenta-related complications (yes/no).

MAIN RESULTS AND THE ROLE OF CHANCE

Increased absolute vascular morphologic development, estimated by positive random intercepts of the uPVS characteristics, is associated with increased embryonic growth, reflected by crown-rump length (endpoints β = 0.017, 95% CI [0.009; 0.025], bifurcation points β = 0.012, 95% CI [0.006; 0.018], crossing points β = 0.017, 95% CI [0.008; 0.025], vessel points β = 0.01, 95% CI [0.002; 0.008], and total vascular length β = 0.007, 95% CI [0.003; 0.010], and similarly with embryonic volume and Carnegie stage, all P-values ≤ 0.01. Density of vascular branching was negatively associated with estimated fetal weight in the third trimester (endpoints: uPVV β = -94.972, 95% CI [-185.245; -3.698], bifurcation points: uPVV β = -192.601 95% CI [-360.532; -24.670]) and birth weight percentiles (endpoints: uPVV β = -20.727, 95% CI [-32.771; -8.683], bifurcation points: uPVV β -51.097 95% CI [-72.257; -29.937], and crossing points: uPVV β = -48.604 95% CI [-74.246; -22.961])), all P-values < 0.05. After stratification, the associations were observed in natural conceptions specifically.

LIMITATION, REASONS FOR CAUTION

Although the results of this prospective observational study clearly demonstrate associations between first-trimester utero-placental vascular morphologic development and prenatal growth, further research is required before we can draw firm conclusions about a causal relationship.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings support the hypothesis that morphologic variations in utero-placental vascular development play a role in the vascular mechanisms involved in embryonic and fetal growth and development. Application of the uPVS could benefit our understanding of the pathophysiology underlying placenta-related complications. Future research should focus on the clinical applicability of the uPVS as an imaging marker for the early detection of fetal growth restriction.

STUDY FUNDING/COMPETING INTEREST(S)

This research was funded by the Department of Obstetrics and Gynecology of the Erasmus MC, University Medical Centre, Rotterdam, The Netherlands. There are no conflicts of interest.

TRIAL REGISTRATION NUMBER

Registered at the Dutch Trial Register (NTR6854).

Deciphering the Epigenetic Landscape: Placental Development and Its Role in Pregnancy Outcomes

The placenta stands out as a unique, transitory, and multifaceted organ, essential to the optimal growth and maturation of the fetus. Functioning as a vital nexus between the maternal and fetal circulatory systems, it oversees the critical exchange of nutrients and waste. This exchange is facilitated by placental cells, known as trophoblasts, which adeptly invade and remodel uterine blood vessels. Deviations in placental development underpin a slew of pregnancy complications, notably fetal growth restriction (FGR), preeclampsia (PE), recurrent spontaneous abortions (RSA), and preterm birth. Central to placental function and development is epigenetic regulation. Despite its importance, the intricate mechanisms by which epigenetics influence the placenta are not entirely elucidated. Recently, the scientific community has turned its focus to parsing out the epigenetic alterations during placental development, such as variations in promoter DNA methylation, genomic imprints, and shifts in non-coding RNA expression. By establishing correlations between epigenetic shifts in the placenta and pregnancy complications, researchers are unearthing invaluable insights into the biology and pathophysiology of these conditions. This review seeks to synthesize the latest findings on placental epigenetic regulation, spotlighting its crucial role in shaping fetal growth trajectories and development. Through this lens, we underscore the overarching significance of the placenta in the larger narrative of gestational health.

Do small for gestational age fetuses have placental pathologies?

PURPOSE

Although small for gestational age (SGA) does not cause adverse perinatal outcomes, the placental pathology for fetal growth restricted (FGR) and SGA fetuses is still unknown. The aim of this study is to evaluate the differences between placentas of early onset FGR, late onset FGR, SGA, and appropriate for gestational age (AGA) pregnancies in the manner of microvasculature and expression of anti-angiogenic PEDF factor and CD68.

METHODS

The study included four groups (early onset FGR, late onset FGR, SGA and AGA). Placental samples were obtained just after labor in all of the groups. Degenerative criteria were investigated with Hematoxylin-eosin staining. Immunohistochemical evaluation with H score and m RNA levels of Cluster of differentiation 68 (CD68) and pigment epithelium derived factor (PEDF) were performed for each group.

RESULTS

The highest levels of degeneration were detected in the early onset FGR group. In means of degeneration SGA placentas were found to be worse than the AGA placentas. The intensity of PEDF and CD68 were significant in early FGR, the late FGR and SGA groups compared to the AGA group (p < 0.001). The mRNA level results of the PEDF and CD68 were also parallel to the immunostaining results.

CONCLUSION

Although SGA fetuses are considered constitutionally small, the SGA placentas also demonstrated signs of degeneration similar to the FGR placentas. These degenerative signs were not seen among the AGA placentas.

Liposome-Encapsulated Anti-inflammatory Proteins for Targeted Delivery to the Placenta to Treat Fetal Growth Restriction

Fetal growth restriction (FGR), the failure of a fetus to reach its genetically determined growth potential, is a serious complication affecting up to 10% of pregnancies. FGR is a major risk factor for stillbirth and, in the survivors, neurodevelopmental disorders. We have recently identified that the anti-inflammatory and pro-resolving molecule, lipoxin A4 (LXA4) and its soluble receptor, formyl-peptide receptor-2 (FPR-2) are significantly decreased in human placentas from FGR pregnancy. The LXA4 synthetic analog Compound 43 (C43) is considered a safe, anti-inflammatory therapy and is being developed as a treatment for disease conditions with an inflammatory basis, for example, asthma in children. Identification of therapies to treat FGR in utero comes with the need to mitigate their potential side effects and the use of nanoparticle-mediated delivery systems could facilitate this. Our current studies are focused on targeting the resolution of inflammation observed in FGR placentas, by synthesizing liposome-encapsulated C43 as a novel therapeutic to improve placental function in FGR. In this chapter, we provide a detailed methodological procedure for the preparation of liposomes and conjugation of the peptide sequences, which selectively bind to the outer placental syncytiotrophoblast layer or the vascular endothelium of the uterine spiral arterioles.

Human placental vascular and perivascular cell heterogeneity differs between first trimester and term, and in pregnancies affected by foetal growth restriction

Growth-restricted placentae have a reduced vascular network, impairing exchange of nutrients and oxygen. However, little is known about the differentiation events and cell types that underpin normal/abnormal placental vascular formation and function. Here, we used 23-colour flow cytometry to characterize placental vascular/perivascular populations between first trimester and term, and in foetal growth restriction (FGR). First-trimester endothelial cells had an immature phenotype (CD144+/lowCD36-CD146low), while term endothelial cells expressed mature endothelial markers (CD36+CD146+). At term, a distinct population of CD31low endothelial cells co-expressed mesenchymal markers (CD90, CD26), indicating a capacity for endothelial to mesenchymal transition (EndMT). In FGR, compared with normal pregnancies, endothelial cells constituted 3-fold fewer villous core cells (P < 0.05), contributing to an increased perivascular: endothelial cell ratio (2.6-fold, P < 0.05). This suggests that abnormal EndMT may play a role in FGR. First-trimester endothelial cells underwent EndMT in culture, losing endothelial (CD31, CD34, CD144) and gaining mesenchymal (CD90, CD26) marker expression. Together this highlights how differences in villous core cell heterogeneity and phenotype may contribute to FGR pathophysiology across gestation.

Features and Comparative Characteristics of Fucosylated Glycans Expression in Endothelial Glycocalyx of Placental Terminal Villi in Patients with Preeclampsia Treated with Different Antihypertensive Regimens

Antihypertensive therapy is an essential part of management of patients with preeclampsia (PE). Methyldopa (Dopegyt®) and nifedipine (Cordaflex®) are basic medications of therapy since they stabilize blood pressure without affecting the fetus. Their effect on the endothelium of placental vessels has not yet been studied. In this study, we analyzed the effect of antihypertensive therapy on the expression of fucosylated glycans in fetal capillaries of placental terminal villi in patients with early-onset PE (EOPE) and late-onset PE (LOPE), and determined correlation between their expression and mother's hemodynamic parameters, fetoplacental system, factors reflecting inflammatory response, and destructive processes in the endothelial glycocalyx (eGC). A total of 76 women were enrolled in the study: the comparison group consisted of 15 women with healthy pregnancy, and the main group comprised 61 women with early-onset and late-onset PE, who received one-component or two-component antihypertensive therapy. Hemodynamic status was assessed by daily blood pressure monitoring, dopplerometry of maternal placental and fetoplacental blood flows, and the levels of IL-18, IL-6, TNFα, galectin-3, endocan-1, syndecan-1, and hyaluronan in the blood of the mother. Expression of fucosylated glycans was assessed by staining placental sections with AAL, UEA-I, LTL lectins, and anti-LeY MAbs. It was found that (i) expression patterns of fucosylated glycans in eGC capillaries of placental terminal villi in EOPE and LOPE are characterized by predominant expression of structures with a type 2 core and have a similar pattern of quantitative changes, which seems to be due to the impact of one-component and two-component antihypertensive therapy on their expression; (ii) correlation patterns indicate interrelated changes in the molecular composition of eGC fucoglycans and indicators reflecting changes in maternal hemodynamics, fetoplacental hemodynamics, and humoral factors associated with eGC damage. The presented study is the first to demonstrate the features of placental eGC in women with PE treated with antihypertensive therapy. This study also considers placental fucoglycans as a functional part of the eGC, which affects hemodynamics in the mother-placenta-fetus system.

Assessment of first-trimester utero-placental vascular morphology by 3D power Doppler ultrasound image analysis using a skeletonization algorithm: the Rotterdam Periconception Cohort

STUDY QUESTION

Can three-dimensional (3D) Power Doppler (PD) ultrasound and a skeletonization algorithm be used to assess first-trimester development of the utero-placental vascular morphology?

SUMMARY ANSWER

The application of 3D PD ultrasonography and a skeletonization algorithm facilitates morphologic assessment of utero-placental vascular development in the first trimester and reveals less advanced vascular morphologic development in pregnancies with placenta-related complications than in pregnancies without placenta-related complications.

WHAT IS KNOWN ALREADY

Suboptimal development of the utero-placental vasculature is one of the main contributors to the periconceptional origin of placenta-related complications. The nature and attribution of aberrant vascular structure and branching patterns remain unclear, as validated markers monitoring first-trimester utero-placental vascular morphologic development are lacking.

STUDY DESIGN, SIZE, DURATION

In this prospective observational cohort, 214 ongoing pregnancies were included before 10 weeks gestational age (GA) at a tertiary hospital between January 2017 and July 2018, as a subcohort of the ongoing Rotterdam Periconception Cohort study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

By combining 3D PD ultrasonography and virtual reality, utero-placental vascular volume (uPVV) measurements were obtained at 7, 9 and 11 weeks GA. A skeletonization algorithm was applied to the uPVV measurements to generate the utero-placental vascular skeleton (uPVS), a network-like structure containing morphologic characteristics of the vasculature. Quantification of vascular morphology was performed by assigning a morphologic characteristic to each voxel in the uPVS (end-, vessel-, bifurcation- or crossing-point) and calculating total vascular network length. A Mann–Whitney U test was performed to investigate differences in morphologic development of the first-trimester utero-placental vasculature between pregnancies with and without placenta-related complications. Linear mixed models were used to estimate trajectories of the morphologic characteristics in the first trimester.

MAIN RESULTS AND THE ROLE OF CHANCE

All morphologic characteristics of the utero-placental vasculature increased significantly in the first trimester (P < 0.005). In pregnancies with placenta-related complications (n = 54), utero-placental vascular branching was significantly less advanced at 9 weeks GA (vessel points P = 0.040, bifurcation points P = 0.050, crossing points P = 0.020, total network length P = 0.023). Morphologic growth trajectories remained similar after adjustment for parity, conception mode, foetal sex and occurrence of placenta-related complications.

LIMITATIONS, REASONS FOR CAUTION

The tertiary setting of this prospective observational study provides high internal, but possibly limited external, validity. Extrapolation of the study’s findings should therefore be addressed with caution.

WIDER IMPLICATIONS OF THE FINDINGS

The uPVS enables assessment of morphologic development of the first-trimester utero-placental vasculature. Further investigation of this innovative methodology needs to determine its added value for the assessment of (patho-) physiological utero-placental vascular development.

STUDY FUNDING/COMPETING INTEREST(S)

This research was funded by the Department of Obstetrics and Gynecology of the Erasmus MC, University Medical Centre, Rotterdam, The Netherlands. There are no conflicts of interest.

TRIAL REGISTRATION NUMBER

Registered at the Dutch Trial Register (NTR6854).

From stem cells to spiral arteries: A journey through early placental development

Early placental development lays the foundation of a healthy pregnancy, and numerous tightly regulated processes must occur for the placenta to meet the increasing nutrient and oxygen exchange requirements of the growing fetus later in gestation. Inadequacies in early placental development can result in disorders such as fetal growth restriction that do not present clinically until the second half of gestation. Indeed, growth restricted placentae exhibit impaired placental development and function, including reduced overall placental size, decreased branching of villi and the blood vessels within them, altered trophoblast function, and impaired uterine vascular remodelling, which together combine to reduce placental exchange capacity. This review explores the importance of early placental development across multiple anatomical aspects of placentation, from the stem cells and lineage hierarchies from which villous core cells and trophoblasts arise, through extravillous trophoblast invasion and spiral artery remodelling, and finally remodelling of the larger uterine vessels.

The roles of free iron, heme, haemoglobin, and the scavenger proteins haemopexin and alpha-1-microglobulin in preeclampsia and fetal growth restriction

BACKGROUND

Preeclampsia (PE) is a complex pregnancy syndrome characterised by maternal hypertension and organ damage after 20 weeks of gestation and is associated with an increased risk of cardiovascular disease later in life. Extracellular haemoglobin (Hb) and its metabolites heme and iron are highly toxic molecules and several defence mechanisms have evolved to protect the tissue.

OBJECTIVES

We will discuss the roles of free iron, heme, Hb, and the scavenger proteins haemopexin and alpha-1-microglobulin in pregnancies complicated by PE and fetal growth restriction (FGR).

CONCLUSION

In PE, oxidative stress causes syncytiotrophoblast (STB) stress and increased shedding of placental STB-derived extracellular vesicles (STBEV). The level in maternal circulation correlates with the severity of hypertension and supports the involvement of STBEVs in causing maternal symptoms in PE. In PE and FGR, iron homeostasis is changed, and iron levels significantly correlate with the severity of the disease. The normal increase in plasma volume taking place during pregnancy is less for PE and FGR and therefore have a different impact on, for example, iron concentration, compared to normal pregnancy. Excess iron promotes ferroptosis is suggested to play a role in trophoblast stress and lipotoxicity. Non-erythroid α-globin regulates vasodilation through the endothelial nitric oxide synthase pathway, and hypoxia-induced α-globin expression in STBs in PE placentas is suggested to contribute to hypertension in PE. Underlying placental pathology in PE with and without FGR might be amplified by iron and heme overload causing oxidative stress and ferroptosis. As the placenta becomes stressed, the release of STBEVs increases and affects the maternal vasculature.

Targeted Delivery of Epidermal Growth Factor to the Human Placenta to Treat Fetal Growth Restriction

Placental dysfunction is the underlying cause of pregnancy complications such as fetal growth restriction (FGR) and pre-eclampsia. No therapies are available to treat a poorly functioning placenta, primarily due to the risks of adverse side effects in both the mother and the fetus resulting from systemic drug delivery. The use of targeted liposomes to selectively deliver payloads to the placenta has the potential to overcome these issues. In this study, we assessed the safety and efficacy of epidermal growth factor (EGF)-loaded, peptide-decorated liposomes to improve different aspects of placental function, using tissue from healthy control pregnancies at term, and pregnancies complicated by FGR. Phage screening identified a peptide sequence, CGPSARAPC (GPS), which selectively homed to mouse placentas in vivo, and bound to the outer syncytiotrophoblast layer of human placental explants ex vivo. GPS-decorated liposomes were prepared containing PBS or EGF (50–100 ng/mL), and placental explants were cultured with liposomes for up to 48 h. Undecorated and GPS-decorated liposomes containing PBS did not affect the basal rate of amino acid transport, human chorionic gonadotropin (hCG) release or cell turnover in placental explants from healthy controls. GPS-decorated liposomes containing EGF significantly increased amino acid transporter activity in healthy control explants, but not in placental explants from women with FGR. hCG secretion and cell turnover were unaffected by EGF delivery; however, differential activation of downstream protein kinases was observed when EGF was delivered via GPS-decorated vs. undecorated liposomes. These data indicate that targeted liposomes represent a safe and useful tool for the development of new therapies for placental dysfunction, recapitulating the effects of free EGF.

A Review of Biomechanics Analysis of the Umbilical-Placenta System With Regards to Diseases

Placenta is an important organ that is crucial for both fetal and maternal health. Abnormalities of the placenta, such as during intrauterine growth restriction (IUGR) and pre-eclampsia (PE) are common, and an improved understanding of these diseases is needed to improve medical care. Biomechanics analysis of the placenta is an under-explored area of investigation, which has demonstrated usefulness in contributing to our understanding of the placenta physiology. In this review, we introduce fundamental biomechanics concepts and discuss the findings of biomechanical analysis of the placenta and umbilical cord, including both tissue biomechanics and biofluid mechanics. The biomechanics of placenta ultrasound elastography and its potential in improving clinical detection of placenta diseases are also discussed. Finally, potential future work is listed.

Three-dimensional visualisation of the feto-placental vasculature in humans and rodents

Adequate development of the feto-placental circulation is critical for placental exchange function and healthy fetal growth. Understanding the structure of this circulation and how it informs fetal outcomes is important both in the human placenta, and the rodent, a purported comparative experimental model. Vascular casting and micro-CT imaging approaches enable detailed quantification of the complex vascular relationships in the feto-circulation, and provide detailed data to parameterise in silico models. Here, to assist researchers to apply these technically challenging methods we provide detailed approaches to cast and image; 1) human placentas at the cotyledon-level, and 2) whole rodent placentas.

Cell dynamics in human villous trophoblast

BACKGROUND

Villous cytotrophoblast (vCTB) is a precursor cell population that supports the development of syncytiotrophoblast (vSTB), the high surface area barrier epithelium of the placental villus, and the primary interface between maternal and fetal tissue. In light of increasing evidence that the placenta can adapt to changing maternal environments or, under stress, can trigger maternal disease, we consider what properties of these cells empower them to exert a controlling influence on pregnancy progression and outcome.

OBJECTIVE AND RATIONALE

How are cytotrophoblast proliferation and differentiation regulated in the human placental villus to allow for the increasing demands of the fetal and environmental challenges and stresses that may arise during pregnancy?

SEARCH METHODS

PubMed was interrogated using relevant keywords and word roots combining trophoblast, villus/villous, syncytio/syncytium, placenta, stem, transcription factor (and the individual genes), signalling, apoptosis, autophagy (and the respective genes) from 1960 to the present. Since removal of trophoblast from its tissue environment is known to fundamentally change cell growth and differentiation kinetics, research that relied exclusively on cell culture has not been the main focus of this review, though it is mentioned where appropriate. Work on non-human placenta is not systematically covered, though mention is made where relevant hypotheses have emerged.

OUTCOMES

The synthesis of data from the literature has led to a new hypothesis for vCTB dynamics. We propose that a reversible transition can occur from a reserve population in G0 to a mitotically active state. Cells from the in-cycle population can then differentiate irreversibly to intermediate cells that leave the cycle and turn on genes that confer the capacity to fuse with the overlying vSTB as well as other functions associated with syncytial barrier and transport function. We speculate that alterations in the rate of entry to the cell cycle, or return of cells in the mitotic fraction to G0, can occur in response to environmental challenge. We also review evidence on the life cycle of trophoblast from the time that fusion occurs, and point to gaps in knowledge of how large quantities of fetal DNA arrive in maternal circulation. We critique historical methodology and make a case for research to re-address questions about trophoblast lifecycle and dynamics in normal pregnancy and the common diseases of pre-eclampsia and fetal growth restriction, where altered trophoblast kinetics have long been postulated.

WIDER IMPLICATIONS

The hypothesis requires experimental testing, moving research away from currently accepted methodology towards a new standard that includes representative cell and tissue sampling, assessment of cell cycle and differentiation parameters, and robust classification of cell subpopulations in villous trophoblast, with due attention to gestational age, maternal and fetal phenotype, disease and outcome.

Mesenchymal Stem/Stromal Cells from the Placentae of Growth Restricted Pregnancies Are Poor Stimulators of Angiogenesis

The extensively branched vascular network within the placenta is vital for materno-fetal exchange, and inadequate development of this network is implicated in the pregnancy disorder fetal growth restriction (FGR), where babies are born pathologically small. Placental mesenchymal stem/stromal cells (pMSCs) and placental macrophages both reside in close proximity to blood vessels within the placenta, where they are thought to promote angiogenesis via paracrine mechanisms. However, the relationship between pMSCs, macrophages and placental vascular development has not yet been examined. We aimed to determine if inadequate paracrine stimulation of placental vascular development by pMSCs and macrophages during pregnancy may contribute to the inadequate vascularisation seen in FGR. Media conditioned by MSCs from FGR placentae significantly inhibited endothelial tube formation, compared to conditioned media derived from normal pMSCs. Similarly, macrophages exposed to media conditioned by FGR pMSCs were less able to stimulate endothelial tube formation in comparison to macrophages exposed to media conditioned by normal pMSCs. While MSCs from normal placentae produce a combination of angiogenic and anti-angiogenic cytokines, there were no significant differences in the secretion of the anti-angiogenic cytokines thrombospondin-1, insulin growth factor binding protein-4, or decorin between normal and FGR pMSCs that could explain how FGR pMSCs inhibited endothelial tube formation. Together, these data suggest a dysregulation in the secretion of paracrine factors by pMSCs in FGR placentae. These findings illustrate how cross talk between pro-angiogenic cell types in the placenta may be crucial for adequate angiogenesis.

Peroxisome Proliferator-Activated Receptors (PPAR), fatty acids and microRNAs: Implications in women delivering low birth weight babies

Low birth weight (LBW) babies are associated with neonatal morbidity and mortality and are at increased risk for noncommunicable diseases (NCDs) in later life. However, the molecular determinants of LBW are not well understood. Placental insufficiency/dysfunction is the most frequent etiology for fetal growth restriction resulting in LBW and placental epigenetic processes are suggested to be important regulators of pregnancy outcome. Early life exposures like altered maternal nutrition may have long-lasting effects on the health of the offspring via epigenetic mechanisms like DNA methylation and microRNA (miRNA) regulation. miRNAs have been recognized as major regulators of gene expression and are known to play an important role in placental development. Angiogenesis in the placenta is known to be regulated by transcription factor peroxisome proliferator-activated receptor (PPAR) which is activated by ligands such as long-chain-polyunsaturated fatty acids (LCPUFA). In vitro studies in different cell types indicate that fatty acids can influence epigenetic mechanisms like miRNA regulation. We hypothesize that maternal fatty acid status may influence the miRNA regulation of PPAR genes in the placenta in women delivering LBW babies. This review provides an overview of miRNAs and their regulation of PPAR gene in the placenta of women delivering LBW babies.Abbreviations: AA - Arachidonic Acid; Ago2 - Argonaute2; ALA - Alpha-Linolenic Acid; ANGPTL4 - Angiopoietin-Like Protein 4; C14MC - Chromosome 14 miRNA Cluster; C19MC - Chromosome 19 miRNA Cluster; CLA - Conjugated Linoleic Acid; CSE - Cystathionine γ-Lyase; DHA - Docosahexaenoic Acid; EFA - Essential Fatty Acids; E2F3 - E2F transcription factor 3; EPA - Eicosapentaenoic Acid; FGFR1 - Fibroblast Growth Factor Receptor 1; GDM - Gestational Diabetes Mellitus; hADMSCs - Human Adipose Tissue-Derived Mesenchymal Stem Cells; hBMSCs - Human Bone Marrow Mesenchymal Stem Cells; HBV - Hepatitis B Virus; HCC - Hepatocellular Carcinoma; HCPT - Hydroxycamptothecin; HFD - High-Fat Diet; Hmads - Human Multipotent Adipose-Derived Stem; HSCS - Human Hepatic Stellate Cells; IUGR - Intrauterine Growth Restriction; LA - Linoleic Acid; LBW - Low Birth Weight; LCPUFA - Long-Chain Polyunsaturated Fatty Acids; MEK1 - Mitogen-Activated Protein Kinase 1; MiRNA - MicroRNA; mTOR - Mammalian Target of Rapamycin; NCDs - NonCommunicable Diseases; OA - Oleic Acid; PASMC - Pulmonary Artery Smooth Muscle Cell; PLAG1 - Pleiomorphic Adenoma Gene 1; PPAR - Peroxisome Proliferator-Activated Receptor; PPARα - PPAR alpha; PPARγ - PPAR gamma; PPARδ - PPAR delta; pre-miRNA - precursor miRNA; RISC - RNA-Induced Silencing Complex; ROS - Reactive Oxygen Species; SAT - Subcutaneous Adipose Tissue; WHO - World Health Organization.

Pulsatility effects of flow on vascular tone in the fetoplacental circulation

INTRODUCTION

The regulation of vascular tone in the fetoplacental circulation is governed by endocrine and mechanical forces yielding a relaxed basal state in normal pregnancy. Flow mediated vasodilation, induced by shear stress and endothelial nitric oxide signalling, is key to driving vasorelaxation in this circulation. The pulsatile property of blood flow, as opposed to the flow rate, could provide an additional factor in this regulation, but its effects and signalling have never been explored in the fetoplacental microvasculature.

METHODS

Here, we studied the effects of non-pulsatile and pulsatile flow modalities on vascular resistance in the fetoplacental microcirculation of the human placenta using an ex vivo perfusion model; and examined a potential role for nitric oxide. We also explored whether the placental Doppler velocimetry waveform is sustained within subchorial arteries in vivo.

RESULTS

Pulsatile flow reduced basal impedance to flow during steady state perfusion compared to non-pulsatile flow, signalled through enhanced nitric oxide production. Doppler velocimetry waveforms were visible within the subchorial arteries in vivo.

CONCLUSION

This work suggests that the pulsatile property of flow through the fetoplacental circulation is sensed by the fetoplacental vasculature to mediate a signalling response and provide additional vasodilation of this microcirculation. We speculate that in pregnancy disease, altered amplitude and frequency of the subchorial pulse might impact on vascular function in a compromised high-resistance placental microcirculation.

Tracking placental development in health and disease

Pre-eclampsia and fetal growth restriction arise from disorders of placental development and have some shared mechanistic features. Initiation is often rooted in the maldevelopment of a maternal-placental blood supply capable of providing for the growth requirements of the fetus in later pregnancy, without exerting undue stress on maternal body systems. Here, we review normal development of a placental bed with a safe and adequate blood supply and a villous placenta-blood interface from which nutrients and oxygen can be extracted for the growing fetus. We consider disease mechanisms that are intrinsic to the maternal environment, the placenta or the interaction between the two. Systemic signalling from the endocrine placenta targets the maternal endothelium and multiple organs to adjust metabolism for an optimal pregnancy and later lactation. This signalling capacity is skewed when placental damage occurs and can deliver a dangerous pathogenic stimulus. We discuss the placental secretome including glycoproteins, microRNAs and extracellular vesicles as potential biomarkers of disease. Angiomodulatory mediators, currently the only effective biomarkers, are discussed alongside non-invasive imaging approaches to the prediction of disease risk. Identifying the signs of impending pathology early enough to intervene and ameliorate disease in later pregnancy remains a complex and challenging objective.

Abnormal angiogenesis of placenta in progranulin‑deficient mice

Progranulin (PGRN) is a secreted growth factor involved in pleiotropic functions, particularly angiogenesis. A distinctly different placental expression of PGRN has been reported between normal pregnancies and pregnancies with complications, such as pre‑eclampsia or fetal growth restriction. However, the role of PGRN in placental vascular development remains to be elucidated. In the present study, PGRN‑knockout mice (PGRN‑/‑) were used to investigate the role of PGRN in the development of placental blood vessels and placental formation. Placental weights and pup body weights were significantly lower in the PGRN‑/‑ mice compared with the wild‑type mice. Reduced labyrinthine layer areas and aberrant vascularization were also observed via hematoxylin and eosin staining of PGRN‑/‑ mice at embryonic day 14.5 (E14.5) and E17.5. In addition, the morphological data obtained via immunohistochemistry, immunofluorescence staining and western blotting demonstrated decreased expression levels of the blood vessel markers α‑smooth muscle actin and CD31 in PGRN‑/‑ placentas. Furthermore, vasodilator endothelial nitric oxide synthase was reduced in the PGRN‑/‑ placenta. These results indicated that PGRN serves an essential role in the normal angiogenesis of the placental labyrinth in mice.

Advances in imaging feto-placental vasculature: new tools to elucidate the early life origins of health and disease

Optimal placental function is critical for fetal development, and therefore a crucial consideration for understanding the developmental origins of health and disease (DOHaD). The structure of the fetal side of the placental vasculature is an important determinant of fetal growth and cardiovascular development. There are several imaging modalities for assessing feto-placental structure including stereology, electron microscopy, confocal microscopy, micro-computed tomography, light-sheet microscopy, ultrasonography and magnetic resonance imaging. In this review, we present current methodologies for imaging feto-placental vasculature morphology ex vivo and in vivo in human and experimental models, their advantages and limitations and how these provide insight into placental function and fetal outcomes. These imaging approaches add important perspective to our understanding of placental biology and have potential to be new tools to elucidate a deeper understanding of DOHaD.

The placenta in fetal growth restriction: What is going wrong?

The placenta is essential for the efficient delivery of nutrients and oxygen from mother to fetus to maintain normal fetal growth. Dysfunctional placental development underpins many pregnancy complications, including fetal growth restriction (FGR) a condition in which the fetus does not reach its growth potential. The FGR placenta is smaller than normal placentae throughout gestation and displays maldevelopment of both the placental villi and the fetal vasculature within these villi. Specialized epithelial cells called trophoblasts exhibit abnormal function and development in FGR placentae. This includes an altered balance between proliferation and apoptotic death, premature cellular senescence, and reduced colonisation of the maternal decidual tissue. Thus, the placenta undergoes aberrant changes at the macroscopic to cellular level in FGR, which can limit exchange capacity and downstream fetal growth. This review aims to compile stereological, in vitro, and imaging data to create a holistic overview of the FGR placenta and its pathophysiology, with a focus on the contribution of trophoblasts.

Whole genome miRNA profiling revealed miR-199a as potential placental pathogenesis of selective fetal growth restriction in monochorionic twin pregnancies

INTRODUCTION

Placental-related mechanism of fetal growth restriction (FGR) is still unknown. Here we aimed to profile whole-genome miRNA between selective FGR twin (sFGR-T) and normally larger co-twin (sL-T) in monochorionic (MC) twin pregnancies and to further investigate effect of the miRNA on placental pathogenesis, including angiogenesis and mitochondrial functions.

METHODS

MC twin pregnancies with or without sFGR were recruited, and their placental miRNAs were profiled (n = 3 vs 5). Ratio of placental miRNAs in the sFGR twin pairs (sFGR-T/sL-T) were calculated and compared to that in the control twin pairs (cS-T/cL-T). Differentially expressed miRNAs and associated markers were validated qRT-PCR, immunohistochemistry staining (n = 8 vs 13) and electron microscopy (n = 3 vs 3).

RESULTS

Placental miR-199a-5p was significantly upregulated in sFGR-T (p = 0.004), which was validated by qRT-PCR (1.03 vs 0.56; p = 0.020). Compared to control twin pairs, ratio of CD31-positive vessels and volume density of vessels in sFGR twin pairs was lower (0.65 vs 0.92 and 18.7% vs 36.3%; both p < 0.001), while that of cyclooxygenase 2 (COX2)-positive trophoblast cells was higher (3.50 vs 2.22; p = 0.001), indicating an impaired angiogenesis and oxidative stress in the sFGR placenta. In addition, ratio of mitochondrial DNA (mtDNA) mitochondrial encoded NADH dehydrogenase 1 (MTND1) copy numbers (2.10 vs 0.90; p = 0.013), H-score ratios of mitochondrial markers citrate synthase (CS) and cytochrome c oxidase subunit 4 isoform 1 (COX4, 0.53 vs 0.95, p < 0.001; 0.29 vs 1.06, p < 0.001) in trophoblast cells of sFGR twin pairs were also altered significantly and correlated with angiogenesis. Furthermore, ratio of mitochondrial numbers per trophoblasts (8.67 vs 18.67; p = 0.006) and percentage of swollen mitochondria (84.33 vs 11.33; p = 0.003) were converted significantly, indicating mitochondrial damage.

DISCUSSION

Our results suggested miR-199a-5p may play a role in the placental angiogenesis, oxidative stress and mitochondrial damage and dysfunction as an underlying pathogenesis of sFGR.

Intra-placental arterial Doppler: A marker of fetoplacental vascularity in late-onset placental disease?

INTRODUCTION

Late-gestation adverse pregnancy outcome is associated with reduced placental villous vascularity but rarely with a frankly abnormal umbilical artery Doppler waveform. The clinical utility of umbilical artery Doppler velocimetry in late gestation is limited by poor understanding of what aspect(s) of placental structure and function the impedance reflects. We hypothesized that placental arterial circulation impedance reflects placental vascularity and arterial function.

MATERIAL AND METHODS

This was a secondary analysis of data from the FEMINA2 study, a study of pregnancy outcome after reduced fetal movement. Forty-three pregnancies that delivered within 7 days of ultrasound assessment were examined. Impedance was quantified by pulsatility index (PI) from umbilical, chorionic plate arteries, and intra-placental arteries. Site-specific PI was compared with villous vascularity (CD31 immunostaining) and placental arterial function (wire myography) by regression analysis (P < .01) where factor analysis suggested potential co-variance (Eigen value > 2).

RESULTS

Pulsatility index decreased with proximity to the placental microvasculature (P < .0001). Intra-placental artery PI correlated significantly with vessel number (R²  = 0.40, P = .0007). No significant relations between umbilical or chorionic plate artery PI and villous vascularity were found (P ≥ .11 and P ≥ .042). No significant co-variance was suggested between PI at any Doppler sampling site and ex vivo placental arterial function indices. Measurement reliability (intraclass correlation coefficient) was highest in the umbilical artery (PI 0.75 and 0.50 for intra- and interoperator reliability, respectively) and lowest in the intra-placental arteries (PI 0.55 and 0.41, respectively). Systematic bias in umbilical artery PI was observed between observers, but not at other Doppler sampling sites.

CONCLUSIONS

More vascular placentas ex vivo are associated with reduced intra-placental artery Doppler impedance in utero. Although umbilical (but not intra-placental) artery Doppler PI is associated with adverse outcome after reduced fetal movement, this predictive ability does not appear to be through assessment of placental vascularity or chorionic plate arterial function. The inferior reliability of intra-placental artery Doppler, although similar to previously published reliability of umbilical artery Doppler, impairs its ability to detect subtle differences in placental vascularity, and must be significantly improved before it could be considered a clinically useful test.

Quantitative characterization of rodent feto-placental vasculature morphology in micro-computed tomography images

BACKGROUND AND OBJECTIVE

Optimal development of placental vasculature is critical for fetal growth and health outcomes. Many studies characterizing the vascular structure of the fetal side of the placenta have utilized a range of two-dimensional and three-dimensional (3D) imaging techniques including X-ray micro-computed tomography (micro-CT) following perfusion of the vasculature with a radio-opaque compound. The CT approach has been used to study feto-placental vasculature in rodents and humans. Its inherent advantage is that it reveals the 3D structure in high resolution without destroying the sample. This permits both multiple scanning of the sample and follow-up histological investigations in the same sample. Nevertheless, the applicability of the approach is hampered both by the challenging segmentation of the vasculature and a lack of straightforward methodology to quantitate the feto-placental vascular network. This paper addresses these challenges.

METHODS

An end-to-end methodology is presented for automatically segmenting the vasculature; obtaining a Strahler-ordered rooted-tree representation and extracting quantitative features from its nodes, segments and branches (including volume, length, tortuosity and branching angles). The methodology is demonstrated for rat and mouse placentas at the end of gestation (day 22 and day 18, respectively), perfused with Microfil® and imaged using two different micro-CT scanners.

RESULTS

The 3D visualizations of the resulting vascular trees clearly demonstrate differences between the branching complexity, tree span and tree depth of the mouse and rat placentas. The quantitative characterizations of these trees include not only the fundamental features that have been utilized in other studies of feto-placental vasculature but also several additional features. Boxplots of several of these-tortuosity, number of side branches, number of offspring per branch and branch volume-computed at each Strahler order are presented and interpreted. Differences and similarities between the mouse and rat casts are readily detected.

CONCLUSION

The proposed end-to-end methodology, and the implementation presented using a combination of Amira and Matlab, offers researchers in the field of placental vasculature characterization a straightforward and objective approach for quantifying micro-CT vascular datasets.

Micro-CT and histological investigation of the spatial pattern of feto-placental vascular density

Introduction

There are considerable variations in villous morphology within a normal placenta. However, whether there is a reproducible spatial pattern of variation in villous vascular density is not known. Micro-CT provides three-dimensional volume imaging with spatial resolution down to the micrometre scale. In this study, we applied Micro-CT and histological analysis to investigate the degree of heterogeneity of vascularisation within the placenta.

Method

Ten term placentas were collected at elective caesarean section, perfused with contrast agent and imaged whole with Micro-CT. Eight full depth tissue blocks were then taken from each placenta and imaged. Sections were taken for histological analysis. Data was analysed to investigate vascular fill, and vascular density in relation to location from cord insertion to placental edge at each scale.

Results

Whole placental imaging revealed no spatially consistent difference in villous vessel density within the main placental tissue, although there was a great degree of heterogeneity. Both block imaging and histological analysis found a large degree of heterogeneity of vascular density within placentas, but no strong correlation between villous vascular density and block location (r_s = 0.066, p = 0.7 block imaging, r_s = 0.06, p = 0.6 histological analysis).

Discussion

This work presents a novel method for imaging the human placenta vascular tree using multiscale Micro-CT imaging. It demonstrates that there is a large degree of variation in vascular density throughout normal term human placentas. The three-dimensional data created by this technique could be used, with more advanced computer analysis, to further investigate the structure of the vascular tree.

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Micro-CT and histological investigation of vascular density in the placenta.

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There is a large degree of variation in vascular density throughout placentas.

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This imaging has potential for future spatial investigation of the 3D vascular tree.

The effect of maternal hyperoxygenation on placental perfusion in normal and Fetal Growth Restricted pregnancies using Intravoxel Incoherent Motion

PURPOSE

To evaluate the effect of maternal hyperoxygenation on placental perfusion in normal and Fetal Growth Restricted (FGR) pregnancies using Intravoxel Incoherent Motion (IVIM).

METHODS

Ten FGR pregnancies and twenty-five normal pregnancies underwent IVIM examinations before and after maternal hyperoxygenation (95% O₂, 5% CO₂) using a 1.5T MR scanner. The IVIM parameters (f_p, D_t, D_p) were determined for the placentas of both groups. The IVIM parameters within and between groups and their correlations with Doppler findings were statistically analyzed. ROC analysis was performed to evaluate the diagnostic power of IVIM derived parameters.

RESULTS

Before maternal hyperoxygenation, the perfusion fraction f_p was significantly lower in the FGR group than that in the normal group (22.88±10.29 (%) vs. 36.28±9.70 (%), p = 0.000). After maternal hyperoxygenation, f_p decreased significantly in the normal group (36.28±9.70 (%) vs. 29.93±10.25 (%), p = 0.032), whereas it remained relatively stable in the FGR group (22.88±10.29 (%) vs. 24.38±13.67 (%), p = 0.508). An increase of D_t was found only for the normal group and D_p did not changed significantly after maternal hyperoxygenation. There existed a negative correlation between f_ppre and umbilical artery pulsatility index (PI) (r = -0.385, p < 0.05) as well as D_tpost and PI (r = -0.574, p < 0.01). The f_ppre displayed a best diagnostic power of all parameters with the area under curve (AUC) of 0.912.

CONCLUSION

The perfusion fraction, f_p, is able to distinguish FGR from normal pregnancies by its value pre and by its change (or lack thereof) post maternal hyperoxygenation. IVIM may potentially help improve the diagnosis of placenta function as it relates to disease.

Differences in placental capillary shear stress in fetal growth restriction may affect endothelial cell function and vascular network formation

Fetal growth restriction (FGR) affects 5-10% of pregnancies, leading to clinically significant fetal morbidity and mortality. FGR placentae frequently exhibit poor vascular branching, but the mechanisms driving this are poorly understood. We hypothesize that vascular structural malformation at the organ level alters microvascular shear stress, impairing angiogenesis. A computational model of placental vasculature predicted elevated placental micro-vascular shear stress in FGR placentae (0.2 Pa in severe FGR vs 0.05 Pa in normal placentae). Endothelial cells cultured under predicted FGR shear stresses migrated significantly slower and with greater persistence than in shear stresses predicted in normal placentae. These cell behaviors suggest a dominance of vessel elongation over branching. Taken together, these results suggest (1) poor vascular development increases vessel shear stress, (2) increased shear stress induces cell behaviors that impair capillary branching angiogenesis, and (3) impaired branching angiogenesis continues to drive elevated shear stress, jeopardizing further vascular formation. Inadequate vascular branching early in gestation could kick off this cyclic loop and continue to negatively impact placental angiogenesis throughout gestation.

Three contaminated sites in southern Italy. The Neonatal Environment and Health Outcomes cohort: protocol for a longitudinal birth cohort study

INTRODUCTION

Exposure to environmental contaminants during pregnancy is one of the determinants of child's future health outcomes. The effect of environmental pollution on pregnant women living in heavily polluted areas is of special interest and, in this context, the Neonatal Environment and Health Outcomes (NEHO) cohort will focus on the investigation of (1) toxicants transferred from the environment to the mother and from the mother to the developing fetus and (2) the influence of toxicants on pregnancy outcomes, fetal development and health status during infancy. Because the human placenta is positioned at the interface between the maternal/external environment and the embryo, it can be considered a highly informative matrix regarding many key pregnancy events that can shape infant's future health.

METHODS AND ANALYSIS

The NEHO cohort will enrol an estimated total of 800 pregnant women in three selected National Priority Contaminated Sites in southern Italy. Epidemiological data, concerning maternal health status, lifestyle and pregnancy, are obtained through questionnaires provided to the mother starting from the last 2 months of pregnancy. At delivery, maternal blood, umbilical cord blood and placenta tissue are collected to assess contaminant levels and to clarify how toxicants interact with the placental domain. Furthermore, placental transcriptome is studied in order to explore the interferences of toxicants on the role of the placenta in maternal/fetal interplay. Regular follow-up is planned at 6, 12 and 24 months.

ETHICS AND DISSEMINATION

The study has been approved by all the Ethics Committees of the three National Priority Contaminated Sites involved: the Ethics Committee of the University Hospitals of Messina (18 September 2017, n. 9/2017); the Ethics Committee 'Catania 2' (11 July 2017, n. 38/2017/CECT2); the Ethics Committee of the Region of Calabria (20 July 2017, n. 173). Findings will be disseminated in the scientific community and on a regional basis for appropriate policy actions.

Women's lived experiences of a prenatal diagnosis of fetal growth restriction at the limits of viability: An interpretative phenomenological study

OBJECTIVES

The research team aimed to understand women's lived experiences during pregnancies with poor prognosis following prenatal detection of Fetal Growth Restriction at the limits of viability (FGRLV).

METHODS

Qualitative interviews with six women who had attended a specialist service following a prenatal diagnosis of FGRLV were conducted. The interview data were analysed using interpretative phenomenological analysis.

FINDINGS

Three superordinate themes alongside thirteen subthemes were identified. Theme 1 described 'a fine line between supportive and unhelpful' care experiences. A second theme of 'understanding the situation and decisions to be made' described how women faced many uncertainties. The final theme of 'parental responsibility' reflected how women imagined their futures to have been, exploring their embodied parental role and connection to their unborn or young child.

KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

Women highlighted the importance of maternal healthcare teams providing clear information and reassurance to them. They also reported that prior experiences were important to them in influencing their perception of that pregnancy. Furthermore, women reflected on their desperation for a positive outcome. Understanding these factors can enable maternal healthcare teams to facilitate informed decision-making and provide individualised emotional support for women. Our findings will enable maternal care teams to better support women in similar clinical situations.

Vascular changes in fetal growth restriction: clinical relevance and future therapeutics

Fetal growth restriction (FGR) affects about 5-10% pregnancies and is associated with poorer outcomes in the perinatal period. Additionally, long standing epidemiological data support its association with chronic diseases such as hypertension and diabetes. Cardiac and vascular adaptations in response to chronic hypoxemia due to utero-placental insufficiency are hallmarks of fetal adaptations. Investigators have attempted to identify these changes in the placenta at the microscopic and molecular level. The ex vivo dual perfusion model of the placenta enables the study of placental haemodynamics in growth-restricted pregnancies. Persistent arterial abnormalities (thickness and stiffness) noted on vascular ultrasound during fetal life through to the young-adult age group for those affected by FGR, seem to be a plausible link between in utero events and chronic circulatory diseases. Using these, this review reflects current thought on vascular maladaptive changes in the FGR cohorts and the role in investigating current and future therapeutics.

The Possible Role of Placental Morphometry in the Detection of Fetal Growth Restriction

Fetal growth restriction (FGR) is often the result of placental insufficiency and is characterized by insufficient transplacental transport of nutrients and oxygen. The main underlying entities of placental insufficiency, the pathophysiologic mechanism, can broadly be divided into impairments in blood flow and exchange capacity over the syncytiovascular membranes of the fetal placenta villi. Fetal growth restriction is not synonymous with small for gestational age and techniques to distinguish between both are needed. Placental insufficiency has significant associations with adverse pregnancy outcomes (perinatal mortality and morbidity). Even in apparently healthy survivors, altered fetal programming may lead to long-term neurodevelopmental and metabolic effects. Although the concept of fetal growth restriction is well appreciated in contemporary obstetrics, the appropriate detection of FGR remains an issue in clinical practice. Several approaches have aimed to improve detection, e.g., uniform definition of FGR, use of Doppler ultrasound profiles and use of growth trajectories by ultrasound fetal biometry. However, the role of placental morphometry (placental dimensions/shape and weight) deserves further exploration. This review article covers the clinical relevance of placental morphometry during pregnancy and at birth to help recognize fetuses who are growth restricted. The assessment has wide intra- and interindividual variability with various consequences. Previous studies have shown that a small placental surface area and low placental weight are associated with a slower growth of the fetus. Parameters such as placental surface area, placental volume and placental weight in relation to birth weight can help to identify FGR. In the future, a model including sophisticated antenatal placental morphometry may prove to be a clinically useful method for screening or diagnosing growth restricted fetuses, in order to provide optimal monitoring.

Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

Cell free hemoglobin impairs vascular function and blood flow in adult cardiovascular disease. In this study, we investigated the hypothesis that free fetal hemoglobin (fHbF) compromises vascular integrity and function in the fetoplacental circulation, contributing to the increased vascular resistance associated with fetal growth restriction (FGR). Women with normal and FGR pregnancies were recruited and their placentas collected freshly postpartum. FGR fetal capillaries showed evidence of erythrocyte vascular packing and extravasation. Fetal cord blood fHbF levels were higher in FGR than in normal pregnancies ( P < 0.05) and the elevation of fHbF in relation to heme oxygenase-1 suggests a failure of expected catabolic compensation, which occurs in adults. During ex vivo placental perfusion, pathophysiological fHbF concentrations significantly increased fetal-side microcirculatory resistance ( P < 0.05). fHbF sequestered NO in acute and chronic exposure models ( P < 0.001), and fHbF-primed placental endothelial cells developed a proinflammatory phenotype, demonstrated by activation of NF-κB pathway, generation of IL-1α and TNF-α (both P < 0.05), uncontrolled angiogenesis, and disruption of endothelial cell flow alignment. Elevated fHbF contributes to increased fetoplacental vascular resistance and impaired endothelial protection. This unrecognized mechanism for fetal compromise offers a novel insight into FGR as well as a potential explanation for associated poor fetal outcomes such as fetal demise and stillbirth.-Brook, A., Hoaksey, A., Gurung, R., Yoong, E. E. C., Sneyd, R., Baynes, G. C., Bischof, H., Jones, S., Higgins, L. E., Jones, C., Greenwood, S. L., Jones, R. L., Gram, M., Lang, I., Desoye, G., Myers, J., Schneider, H., Hansson, S. R., Crocker, I. P., Brownbill, P. Cell free hemoglobin in the fetoplacental circulation: a novel cause of fetal growth restriction?

Association of Placental Jets and Mega-Jets With Reduced Villous Density

Spiral arteries (SAs) lie at the interface between the uterus and placenta, and supply nutrients to the placental surface. Maternal blood circulation is separated from the fetal circulation by structures called villous trees. SAs are transformed in early pregnancy from tightly coiled vessels to large high-capacity channels, which is believed to facilitate an increased maternal blood flow throughout pregnancy with minimal increase in velocity, preventing damage to delicate villous trees. Significant maternal blood flow velocities have been theorized in the space surrounding the villi (the intervillous space, IVS), particularly when SA conversion is inadequate, but have only recently been visualized reliably using pulsed wave Doppler ultrasonography. Here, we present a computational model of blood flow from SA openings, allowing prediction of IVS properties based on jet length. We show that jets of flow observed by ultrasound are likely correlated with increased IVS porosity near the SA mouth and propose that observed mega-jets (flow penetrating more than half the placental thickness) are only possible when SAs open to regions of the placenta with very sparse villous structures. We postulate that IVS tissue density must decrease at the SA mouth through gestation, supporting the hypothesis that blood flow from SAs influences villous tree development.

Chorionic vascular "fit" in the human placenta: Relationship to fetoplacental outcomes

BACKGROUND

Novel measures of the chorionic plate and vessels are used to test the hypothesis that variation in placental structure is correlated with reduced birth weight (BW) independent of placental weight (PW), suggesting functionally compromised placentas.

METHODS

916 mothers recruited to the Pregnancy, Infection and Nutrition Study delivering singleton live born infants at >30 gestational weeks had placentas collected, digitally photographed and weighed prior to formalin fixation. The fetal-placental weight ratio (FPR) was calculated as birthweight/placental weight. Beta (beta) was calculated as ln(PW)/ln(BW). Chorionic disk perimeter was traced and chorionic surface shape (CS) area was calculated. "Fit" was defined as the ratio of the area of the vascular to the full chorionic surface area. The sites at which chorionic vessels dived beneath the chorionic surface were marked to calculate the chorionic surface vessel (CV) area. The centroids of shapes, the distance between centroids and other measures of shape irregularities were calculated. Principal components analysis (PCA) created three independent factors. Factors were used in regression analyses to explore relations to birth weight, trimmed placental weight, FPR, and beta. Specific measures of shape irregularity were also examined in regression analyses for interrelationships and to predict birth weight, placental weight, FPR, and beta.

RESULTS

Variables related to disk size (CS area, perimeter) were correlated with BW, GA, trimmed PW and beta. "Fit" (the ratio of CV area to CS area), measures of shape irregularities, and the distance between the cord insertion and the centroids of surface and vascular areas were also correlated with one or more of the clinical outcome variables. PCA yielded three factors that had independent effects on birth weight, placental weight, the fetal-placental weight ratio, and beta (each p < 0.0001). Addition of GA did not alter the factors' associations with outcomes. Chorionic "fit" (ratio of areas), also included within the factor analysis, was a positive predictor of birth weight (p = 0.005) and FPR (p = 0.002) and a negative predictor of beta (p = 0.01). Fit was statistically significantly associated with greater distances between the umbilical cord insertion site and the CS (p < 0.001) and CV centroids (p < 0.001), and to lesser displacement between CS and CV centroids (p < 0.001).

CONCLUSIONS

Measures of CS and CV account for variation in placental efficiency defined by beta, independent of GA. Macroscopic placenta measurements can identify suboptimal placental development.

Placental Dysfunction Underlies Increased Risk of Fetal Growth Restriction and Stillbirth in Advanced Maternal Age Women

Pregnancies in women of advanced maternal age (AMA) are susceptible to fetal growth restriction (FGR) and stillbirth. We hypothesised that maternal ageing is associated with utero-placental dysfunction, predisposing to adverse fetal outcomes. Women of AMA (≥35 years) and young controls (20-30 years) with uncomplicated pregnancies were studied. Placentas from AMA women exhibited increased syncytial nuclear aggregates and decreased proliferation, and had increased amino acid transporter activity. Chorionic plate and myometrial artery relaxation was increased compared to controls. AMA was associated with lower maternal serum PAPP-A and sFlt and a higher PlGF:sFlt ratio. AMA mice (38-41 weeks) at E17.5 had fewer pups, more late fetal deaths, reduced fetal weight, increased placental weight and reduced fetal:placental weight ratio compared to 8-12 week controls. Maternofetal clearance of 14C-MeAIB and 3H-taurine was reduced and uterine arteries showed increased relaxation. These studies identify reduced placental efficiency and altered placental function with AMA in women, with evidence of placental adaptations in normal pregnancies. The AMA mouse model complements the human studies, demonstrating high rates of adverse fetal outcomes and commonalities in placental phenotype. These findings highlight placental dysfunction as a potential mechanism for susceptibility to FGR and stillbirth with AMA.

Selective Targeting of a Novel Vasodilator to the Uterine Vasculature to Treat Impaired Uteroplacental Perfusion in Pregnancy

Fetal growth restriction (FGR) in pregnancy is commonly caused by impaired uteroplacental blood flow. Vasodilators enhance uteroplacental perfusion and fetal growth in humans and animal models; however, detrimental maternal and fetal side effects have been reported. We hypothesised that targeted uteroplacental delivery of a vasodilator would enhance drug efficacy and reduce the risks associated with drug administration in pregnancy. Phage screening identified novel peptides that selectively accumulated in the uteroplacental vasculature of pregnant mice. Following intravenous injection, the synthetic peptide CNKGLRNK selectively bound to the endothelium of the uterine spiral arteries and placental labyrinth in vivo; CNKGLRNK-decorated liposomes also selectively bound to these regions. The nitric oxide donor 2-[[4-[(nitrooxy)methyl]benzoyl]thio]-benzoic acid methyl ester (SE175) induced significant relaxation of mouse uterine arteries and human placental arteries in vitro; thus, SE175 was encapsulated into these targeted liposomes and administered to healthy pregnant C57BL/6J mice or endothelial nitric oxide synthase knockout (eNOS-/-) mice, which exhibit impaired uteroplacental blood flow and FGR. Liposomes containing SE175 (0.44mg/kg) or PBS were administered on embryonic (E) days 11.5, 13.5, 15.5 and 17.5; fetal and placental weights were recorded at term and compared to mice injected with free PBS or SE175. Targeted uteroplacental delivery of SE175 had no effect on fetal weight in C57BL/6J mice, but significantly increased fetal weight and mean spiral artery diameter, and decreased placental weight, indicative of improved placental efficiency, in eNOS-/- mice; free SE175 had no effect on fetal weight or spiral artery diameter. Targeted, but not free SE175 also significantly reduced placental expression of 4-hydroxynonenal, cyclooxygenase-1 and cyclooxygenase-2, indicating a reduction in placental oxidative stress. These data suggest that exploiting vascular targeting peptides to selectively deliver SE175 to the uteroplacental vasculature may represent a novel treatment for FGR resulting from impaired uteroplacental perfusion.

MR Imaging Measurements of Altered Placental Oxygenation in Pregnancies Complicated by Fetal Growth Restriction

Purpose To evaluate oxygen-enhanced and blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging parameters in normal pregnancies and those complicated by fetal growth restriction (FGR). Materials and Methods This case-control study was approved by the local research ethics committee. Informed consent was obtained from all subjects. From October 2010 to October 2015, 28 women with uncomplicated pregnancies (individualized birthweight ratio [IBR] >20th percentile and delivery >37 weeks) and 23 with pregnancies complicated by FGR (IBR <5th percentile and abnormal Doppler ultrasonography [US] studies) underwent MR imaging. Differences in placental longitudinal R1 (1/T1) and transverse R2* (1/T2*) were quantified, with subjects breathing either air or oxygen. The difference in R1 (ΔR1) after hyperoxia was converted to change in partial pressure of oxygen (ΔPo₂). Data were acquired prospectively, with retrospective interpretation of group differences (unpaired t tests). Diagnostic models were developed by using logistic regression analysis with gestational age as a covariate. Results The mean baseline R1 and R2* for normal pregnancies (R1: 0.59 sec^-1, 95% confidence interval [CI]: 0.58 sec^-1, 0.60 sec^-1; R2*: 17 sec^-1, 95% CI: 14 sec^-1, 20 sec^-1) were significantly different from those of pregnancies complicated by FGR (R1: 0.63 sec^-1, 95% CI: 0.62 sec^-1, 0.65 sec^-1; R2*: 26 sec^-1, 95% CI: 22 sec^-1, 32 sec^-1) (P < .0001). The ΔR1 showed a significant negative association with gestational age (P < .0001) in the combined cohort, with the FGR group having a ΔR1 that was generally 61.5% lower than that in the normal pregnancy group (P = .003). The area under the receiver operating characteristic curve for the differentiation between pregnancy complicated by FGR and normal pregnancy by using ΔPo₂, baseline R1, and baseline R2* was 0.91 (95% CI: 0.82, 0.99). Conclusion R1, R2*, and ΔPo₂ were significantly different between normal pregnancies and those complicated by severe FGR. MR imaging parameters have the potential to help identify placental dysfunction associated with FGR and may have clinical utility in correctly identifying FGR among fetuses that are small for gestational age. A larger prospective study is needed to assess the incremental benefit beyond that offered by US. ^© RSNA, 2017.

Whole organ vascular casting and microCT examination of the human placental vascular tree reveals novel alterations associated with pregnancy disease

Experimental methods that allow examination of the intact vascular network of large organs, such as the human placenta are limited, preventing adequate comparison of normal and abnormal vascular development in pregnancy disease. Our aims were (i) to devise an effective technique for three-dimensional analyses of human placental vessels; (ii) demonstrate the utility of the technique in the comparison of placental vessel networks in normal and fetal growth restriction (FGR) complicated pregnancies. Radiopaque plastic vessel networks of normal and FGR placentas (n = 12/group) were created by filling the vessels with resin and corroding the surrounding tissues. Subsequently, each model was scanned in a microCT scanner, reconstructed into three-dimensional virtual objects and analysed in visualisation programmes. MicroCT imaging of the models defined vessel anatomy to our analyses threshold of 100 µm diameter. Median vessel length density was significantly shorter in arterial but longer in venous FGR networks compared to normals. No significant differences were demonstrable in arterial or venous tortuosity, diameter or branch density. This study demonstrates the potential effectiveness of microCT for ex-vivo examination of human placental vessel morphology. Our findings show significant discrepancies in vessel length density in FGR placentas. The effects on fetoplacental blood flow, and hence nutrient transfer to the fetus, are unknown.

Feeding Your Baby In Utero: How the Uteroplacental Circulation Impacts Pregnancy

The utero-placental circulation links the maternal and fetal circulations during pregnancy, ensuring adequate gas and nutrient exchange, and consequently fetal growth. However, our understanding of this circulatory system remains incomplete. Here, we discuss how the utero-placental circulation is established, how it changes dynamically during pregnancy, and how this may impact on pregnancy success, highlighting how we may address knowledge gaps through advances in imaging and computational modeling approaches.

Placental soluble fms-like tyrosine kinase expression in small for gestational age infants and risk for adverse outcomes

INTRODUCTION

Soluble fms-like tyrosine kinase 1 (sFLT-1) is an anti-angiogenic factor implicated in the pathogenesis of preterm preeclampsia. We evaluated sFLT-1 expression and placental pathology in pregnancies complicated by small for gestational age (SGA) infants (<10th percentile), without evidence of preeclampsia.

METHODS

Clinical and histologic data were compared between groups with high or low sFLT-1 expression determined by immunohistochemistry on archived placentas.

RESULTS

Nineteen of 69 placentas showed high sFLT-1 expression. The high sFLT-1 group had higher predelivery median systolic blood pressure (BP); 140 (interquartile range (IQR) 133-152) vs. 126 (118-139) mm Hg (p = 0.003), and median diastolic BP; 87 (78-94) vs. 77.5 (71-86) mm Hg (p = 0.02). Abnormal umbilical Doppler abnormalities were more prevalent; 89.5% vs. 46% (p = 0.001). These pregnancies delivered earlier; 31.9 weeks (28.3-34.7 weeks) vs. 37.1 weeks (33.7-38.7 weeks) (p < 0.001), and infants had lower birthweight; 980 grams (520-1545 grams) vs. 2087.5 grams (1455-2340 grams) (p < 0.001). Placental-weight to fetal-weight ratios, a marker of vascular insufficiency, was increased in the high sFlt-1 group: 0.18 (0.14-0.28) vs 0.15 (0.13-0.18), p = 0.03. Placentas with high sFLT-1 showed more decidual vasculopathy; 42.1% vs. 10.0% (p = 0.005), infarction; 36.8% vs. 14.0% (p = 0.048), distal villous hypoplasia; 78.9% vs. 36.0% (p = 0.001), and fetal thrombotic vasculopathy; 47.4% vs. 16.0% (p = 0.01).

DISCUSSION

Placental sFLT-1 expression is upregulated in approximately 28% of non-preeclamptic pregnancies complicated by SGA infants. These pregnancies showed increased placental vascular pathology, more umbilical Doppler abnormalities, and earlier delivery with lower birthweight. A subgroup of non-preeclamptic fetal growth restriction with upregulated sFlt-1 expression may share a common pathogenic pathway with preterm preeclampsia. This subgroup is worthy of additional study.

Reduced placental volume and flow in severe growth restricted fetuses

OBJECTIVES

To evaluate placental volume and vascular indices in pregnancies with severe fetal growth restriction and determine their correlations to normal reference ranges and Doppler velocimetry results of uterine and umbilical arteries.

METHODS

Twenty-seven fetuses with estimated weights below the 3rd percentile for gestational age were evaluated. Placental volume and vascular indices, including vascularization, flow, and vascularization flow indices, were measured by three-dimensional ultrasound using a rotational technique and compared to a previously described nomogram. The observed-to-expected placental volume ratio for gestational age and observed-to-expected placental volume ratio for fetal weight were calculated. Placental parameters correlated with the Doppler velocimetry results of uterine and umbilical arteries.

RESULTS

The mean uterine artery pulsatility index was negatively correlated with the observed-to-expected placental volume ratio for gestational age, vascularization index and vascularization flow index. The observed-to-expected placental volume ratio for gestational age and observed-to-expected placental volume ratio for fetal weight and vascularization index were significantly lower in the group with a bilateral protodiastolic notch. No placental parameter correlated with the umbilical artery pulsatility index.

CONCLUSIONS

Pregnancies complicated by severe fetal growth restriction are associated with reduced placental volume and vascularization. These findings are related to changes in uterine artery Doppler velocimetry. Future studies on managing severe fetal growth restriction should focus on combined results of placental three-dimensional ultrasound and Doppler studies of uterine arteries.

The impact of a human IGF-II analog ([Leu27]IGF-II) on fetal growth in a mouse model of fetal growth restriction

Enhancing placental insulin-like growth factor (IGF) availability appears to be an attractive strategy for improving outcomes in fetal growth restriction (FGR). Our approach was the novel use of [Leu(27)]IGF-II, a human IGF-II analog that binds the IGF-II clearance receptor IGF-IIR in fetal growth-restricted (FGR) mice. We hypothesized that the impact of [Leu(27)]IGF-II infusion in C57BL/6J (wild-type) and endothelial nitric oxide synthase knockout (eNOS(-/-); FGR) mice would be to enhance fetal growth and investigated this from mid- to late gestation; 1 mg·kg(-1)·day(-1) [Leu(27)]IGF-II was delivered via a subcutaneous miniosmotic pump from E12.5 to E18.5. Fetal and placental weights recorded at E18.5 were used to generate frequency distribution curves; fetuses <5th centile were deemed growth restricted. Placentas were harvested for immunohistochemical analysis of the IGF system, and maternal serum was collected for measurement of exogenously administered IGF-II. In WT pregnancies, [Leu(27)]IGF-II treatment halved the number of FGR fetuses, reduced fetal(P = 0.028) and placental weight variations (P = 0.0032), and increased the numbers of pups close to the mean fetal weight (131 vs. 112 pups within 1 SD). Mixed-model analysis confirmed litter size to be negatively correlated with fetal and placental weight and showed that [Leu(27)]IGF-II preferentially improved fetal weight in the largest litters, as defined by number. Unidirectional (14C)MeAIB transfer per gram placenta (System A amino acid transporter activity) was inversely correlated with fetal weight in [Leu(27)]IGF-II-treated WT animals (P < 0.01). In eNOS(-/-) mice, [Leu(27)]IGF-II reduced the number of FGR fetuses(1 vs. 5 in the untreated group). The observed reduction in FGR pup numbers in both C57 and eNOS(-/-) litters suggests the use of this analog as a means of standardizing and rescuing fetal growth, preferentially in the smallest offspring.

Placental Features of Late-Onset Adverse Pregnancy Outcome

Objective

Currently, no investigations reliably identify placental dysfunction in late pregnancy. To facilitate the development of such investigations we aimed to identify placental features that differ between normal and adverse outcome in late pregnancy in a group of pregnancies with reduced fetal movement.

Methods

Following third trimester presentation with reduced fetal movement (N = 100), placental structure ex vivo was measured. Placental function was then assessed in terms of (i) chorionic plate artery agonist responses and length-tension characteristics using wire myography and (ii) production and release of placentally derived hormones (by quantitative polymerase chain reaction and enzyme linked immunosorbant assay of villous tissue and explant conditioned culture medium).

Results

Placentas from pregnancies ending in adverse outcome (N = 23) were ~25% smaller in weight, volume, length, width and disc area (all p<0.0001) compared with those from normal outcome pregnancies. Villous and trophoblast areas were unchanged, but villous vascularity was reduced (median (interquartile range): adverse outcome 10 (10–12) vessels/mm² vs. normal outcome 13 (12–15), p = 0.002). Adverse outcome pregnancy placental arteries were relatively insensitive to nitric oxide donated by sodium nitroprusside compared to normal outcome pregnancy placental arteries (50% Effective Concentration 30 (19–50) nM vs. 12 (6–24), p = 0.02). Adverse outcome pregnancy placental tissue contained less human chorionic gonadotrophin (20 (11–50) vs. 55 (24–102) mIU/mg, p = 0.007) and human placental lactogen (11 (6–14) vs. 27 (9–50) mg/mg, p = 0.006) and released more soluble fms-like tyrosine kinase-1 (21 (13–29) vs. 5 (2–15) ng/mg, p = 0.01) compared with normal outcome pregnancy placental tissue.

Conclusion

These data provide a description of the placental phenotype of adverse outcome in late pregnancy. Antenatal tests that accurately reflect elements of this phenotype may improve its prediction.