The human first trimester gestational sac limits rather than facilitates oxygen transfer to the foetus--a review

Unveiling the human fetal-maternal interface during the first trimester: biophysical knowledge and gaps

The intricate interplay between the developing placenta and fetal-maternal interactions is critical for pregnancy outcomes. Despite advancements, gaps persist in understanding biomechanics, transport processes, and blood circulation parameters, all of which are crucial for safe pregnancies. Moreover, the complexity of fetal-maternal interactions led to conflicting data and methodological variations. This review presents a comprehensive overview of current knowledge on fetal-maternal interface structures, with a particular focus on the first trimester. More in detail, the embryological development, structural characteristics, and physiological functions of placental chorionic plate and villi, fetal membranes and umbilical cord are discussed. Furthermore, a description of the main structures and features of maternal and fetal fluid dynamic exchanges is provided. However, ethical constraints and technological limitations pose still challenges to studying early placental development directly, which calls for sophisticated in vitro, microfluidic organotypic models for advancing our understanding. For this, knowledge about key in vivo parameters are necessary for their design. In this scenario, the integration of data from later gestational stages and mathematical/computational simulations have proven to be useful tools. Notwithstanding, further research into cellular and molecular mechanisms at the fetal-maternal interface is essential for enhancing prenatal care and improving maternal and fetal health outcomes.

Placenta and maternal endothelium during preeclampsia: Disruption of the glycocalyx explains increased inositol phosphoglycans and angiogenic factors in maternal blood

The etiology of the pregnancy syndrome preeclampsia is still unclear, while most hypotheses center on the placenta as the major contributor of the syndrome. Especially changes of the placental metabolism, including the use of glucose to produce energy, are important features. As an example, inositol phosphoglycan P-type molecules, second messengers involved in the glucose metabolism of all cells, can be retrieved from maternal urine of preeclamptic women, even before the onset of clinical symptoms. Alterations in the placental metabolism may subsequently lead to negative effects on the plasma membrane of the placental syncytiotrophoblast. This in turn may have deleterious effects on the glycocalyx of this layer and a disruption of this layer in all types of preeclampsia. The interruption of the glycocalyx in preeclampsia may result in changes of inositol phosphoglycan P-type signaling pathways and the release of these molecules as well as the release of soluble receptors such as sFlt-1 and sEndoglin. The release of placental factors later affects the maternal endothelium and disrupts the endothelial glycocalyx as well. This in turn may pave the way for edema, endothelial dysfunction, coagulation, all typical symptoms of preeclampsia.

Hypoxia Inducible Factors (HIF1α and HIF3α) are differentially methylated in preeclampsia placentae and are associated with birth outcomes

Preeclampsia is a placental vascular pathology and hypoxia is known to influence placental angiogenesis. Hypoxia Inducible Factors (HIF1α and HIF3α) mediate the response to cellular oxygen concentration and bind to hypoxia response element of target genes. However the mechanism regulating above activity is not well-understood. We investigated if placental DNA methylation (DNAm) and expression of HIF1α and 3α genes are altered and associated with pre-eclampsia, placental weight and birth outcomes. Using a cohort comprising women with preeclampsia [N = 100, delivering at term (N = 43) and preterm (N = 57)] and normotensive controls (N = 100), we analysed DNAm in HIF1α and 3α, and their mRNA expression in placentae, employing pyrosequencing and quantitative real-time PCR, respectively. We observed significant hypermethylation at cg22891070 of HIF3α in preeclampsia placentae compared to controls (β = 1.5%, p = 0.04). CpG8 in the promoter region of HIF1α, showed marginally significant hypomethylation in preterm preeclampsia compared to controls (β = - 0.15%, p = 0.055). HIF1α expression was significantly lower in preterm preeclampsia compared to controls (mean ± SE = 10.16 ± 2.00 vs 4.25 ± 0.90, p = 0.04). Further, DNAm in HIF1α promoter region was negatively associated with its expression levels (β =  - 0.165, p = 0.024). Several CpGs in HIF1α were negatively associated with placental weight and birth outcomes including birth weight (β range =  - 0.224-0.300) and birth length [β range =  - 0.248 to - 0.301 (p < 0.05 for all)]. Overall, we demonstrate altered DNAm in HIF1α and HIF3α in preeclampsia placentae, also associated with various birth outcomes. Correlation of DNAm in HIF1α and its expression suggests a possible role in the pathogenesis of pre-eclampsia. Further investigations on interactions between HIF1α and HIF3α in preeclampsia would be interesting.

The human placenta: new perspectives on its formation and function during early pregnancy

The placenta has evolved to support the development of the embryo and fetus during the different intrauterine periods of life. By necessity, its development must precede that of the embryo. There is now evidence that during embryogenesis and organogenesis, the development of the human placenta is supported by histotrophic nutrition secreted from endometrial glands rather than maternal blood. These secretions provide a plentiful supply of glucose, lipids, glycoproteins and growth factors that stimulate rapid proliferation and differentiation of the villous trophoblast. Furthermore, evidence from endometrial gland organoids indicates that expression and secretion of these products are upregulated following sequential exposure to oestrogen, progesterone and trophoblastic and decidual hormones, in particular prolactin. Hence, a feed-forward signalling dialogue is proposed among the trophoblast, decidua and glands that enables the placenta to stimulate its own development, independent of that of the embryo. Many common complications of pregnancy represent a spectrum of disorders associated with deficient trophoblast proliferation. Increasing evidence suggests that this spectrum is mirrored by one of impaired decidualization, potentially compromising histotroph secretion through diminished prolactin secretion and reduced gland function. Optimizing endometrial wellbeing prior to conception may therefore help to prevent common pregnancy complications, such as miscarriage, growth restriction and pre-eclampsia.

First‐trimester plasma extracellular heat shock proteins levels and risk of preeclampsia

Preeclampsia (PE) occurs annually in 8% of pregnancies. Patients without risk factors represent 10% of these. There are currently no first-trimester biochemical markers that accurately predict PE. An increase in serum 60- and 70-KDa extracellular heat shock proteins (eHsp) has been shown in patients who developed PE at 34 weeks. We sought to determine whether there is a relationship between first-trimester eHsp and the development of PE. This was a prospective cohort study performed at a third level hospital in Mexico City from 2019 to 2020. eHsp levels were measured during the first-trimester ultrasound in singleton pregnancies with no comorbidities. First-trimester eHsp levels and biochemical parameters of organ dysfunction were compared between patients who developed preeclampsia and those who did not. All statistical analyses and model of correlation (r) between eHsp and clinical parameter were performed using bootstrapping R-software. p-values <0.05 were considered significant. The final analysis included 41 patients. PE occurred in 11 cases. eHsp-60 and eHsp-70 were significantly higher at 12 weeks in patients who developed PE (p = 0.001), while eHsp-27 was significantly lower (p = 0.004). Significant differences in first-trimester eHsp concentration suggest that these are possible early biomarkers useful for the prediction of PE.

The Role of Dietary Polyphenols in Pregnancy and Pregnancy-Related Disorders

Polyphenols are a group of phytochemicals with extensive biological functions and health-promoting potential. These compounds are present in most foods of plant origin and their increased widespread availability through the intake of nutritional supplements, fortified foods, and beverages, has also led to increased exposure throughout gestation. In this narrative review, we focus on the role of polyphenols in both healthy and pathological pregnancy. General information related to their classification and function is followed by an overview of their known effects in early-pregnancy events, including the current insights into molecular mechanisms involved. Further, we provide an overview of their involvement in some of the most common pregnancy-associated pathological conditions, such as preeclampsia and gestational diabetes mellitus. Additionally, we also discuss the estimated possible risk of polyphenol consumption on pregnancy outcomes. The consumption of dietary polyphenols during pregnancy needs particular attention considering the possible effects of polyphenols on the mechanisms involved in maternal adaptation and fetal development. Further studies are strongly needed to unravel the in vivo effects of polyphenol metabolites during pregnancy, as well as their role on advanced maternal age, prenatal nutrition, and metabolic risk of the offspring.

The role of miRNA-210 in pre-eclampsia development

MicroRNAs (miRNAs) are a class of small non-coding, single-stranded RNAs (ribonucleic acids) that play important roles in many vital processes through their impact on gene expression. One such miRNA, miR210, represents a hypoxia-induced cellular miRNA group that hold a variety of functions. This review article highlights the importance of miR-210 in the development of pre-eclampsia.KEY MESSAGEmiR-210 is a promising biomarker for monitoring pregnancy with pre-eclampsia. Overexpression of miR-210 had a negative impact on the process of cell migration and trophoblast invasion.

Human placental development and function

The placenta is a transient fetal organ that plays a critical role in the health and wellbeing of both the fetus and its mother. Functionally, the placenta sustains the growth of the fetus as it facilitates delivery of oxygen and nutrients and removal of waste products. Not surprisingly, defective early placental development is the primary cause of common disorders of pregnancy, including recurrent miscarriage, fetal growth restriction, pre-eclampsia and stillbirth. Adverse pregnancy conditions will also affect the life-long health of the fetus via developmental programming[1]. Despite its critical importance in reproductive success and life-long health, our understanding of placental development is not extensive, largely due to ethical limitations to studying early or chronological placental development, lack of long-term in vitro models, or comparative animal models. In this review, we examine current knowledge of early human placental development, discuss the critical role of the maternal endometrium and of the fetal-maternal dialogue in pregnancy success, and we explore the latest models of trophoblast and endometrial stem cells. In addition, we discuss the role of oxygen in placental formation and function, how nutrient delivery is mediated during the periods of histotrophic nutrition (uptake of uterine secretions) and haemotrophic nutrition (exchange between the maternal and fetal circulations), and how placental endocrine function facilitates fetal growth and development.

Selection on embryonic haemoglobin in an elevational generalist songbird

Animals developing at high elevation experience a suite of environmental challenges, most notably the low partial pressure of oxygen (PO₂) in ambient air. In low PO₂, bird species with high-elevation ancestry consistently demonstrate higher hatching success than lowland counterparts, suggesting highland birds are adapted to restricted O₂ (hypoxia) in early development. Haemoglobin (Hb), the critical oxygen-transport protein, is a likely target of PO₂-related selection across ontogeny since Hb isoforms expressed at distinct developmental stages demonstrate different O₂ affinities. To test if Hb function is under PO₂-related selection at different ontogenetic stages, we sampled a songbird, the hooded siskin (Spinus magellanicus), across two approximately 4000 m elevational transects. We sequenced all of the loci that encode avian Hb isoforms, and tested for signatures of spatially varying selection by comparing divergence patterns in Hb loci to other loci sampled across the genome. We found strong signatures of diversifying selection at non-synonymous sites in loci that contribute to embryonic (α^π, β^H) and definitive (β^A) Hb isoforms. This is the first evidence for selection on embryonic haemoglobin in high-elevation Neoaves. We conclude that selection on Hb function at brief, but critical stages of ontogeny may be a vital component to high elevation adaptation in birds.

Vascular Malperfusion – As a Morphological Pattern of Preeclampsia

Introduction. The system « mother-placenta-fetus » is in a complex functional balance, and dysfunction of any of the components can compromise others. The placenta plays an important role in the development of preeclampsia, since preeclampsia can occur in the absence of a fetus, but in the presence of a trophoblast. In this regard, the study of morphological placental patterns in preeclampsia can give an idea of preeclampsia as a pathology in general, as well as its relationship with hypoxic damage to the fetus. Aim.  Identification of morphological patterns of placental lesions associated with preeclampsia. Materials and methods. A retrospective morphological study of 355 placentas sent for histological examination in the period from 2015 to 2020 was carried out. During the analyzed period, 184 placentas from pregnancies with an established diagnosis of preeclampsia and 171 placentas from pregnancies with a physiological course were studied. Results. It has been established that preeclampsia is associated with a smaller mass, size and height of the placenta. As morphological patterns associated with preeclampsia, such histological signs of maternal vascular malperfusion, such as infarcts, arterial atherosclerosis, etc., were identified. Conclusions. The heterogeneity of clinical and histological signs associated with both the physiological and pathological course of pregnancy reflects the different gestational age of the onset of the disease and the stage of development of the adaptive capabilities of the placenta. Identification of morphological patterns associated with hypoxic damage to the fetus allows us to identify a group of newborns with a high risk of chronic hypoxic damage in the perinatal period and to stratify the risk group in the postnatal period in order to reduce infant morbidity and mortality.

The Role of Type I and Type II NKT Cells in Materno-Fetal Immunity

NKT cells represent a small but significant immune cell population as being a part of and bridging innate and adaptive immunity. Their ability to exert strong immune responses via cytotoxicity and cytokine secretion makes them significant immune effectors. Since pregnancy requires unconventional maternal immunity with a tolerogenic phenotype, investigation of the possible role of NKT cells in materno-fetal immune tolerance mechanisms is of particular importance. This review aims to summarize and organize the findings of previous studies in this field. Data and information about NKT cells from mice and humans will be presented, focusing on NKT cells characteristics during normal pregnancy in the periphery and at the materno-fetal interface and their possible involvement in female reproductive failure and pregnancy complications with an immunological background.

The Role of Oxidative Stress and Antioxidant Balance in Pregnancy

It has been widely known that oxidative stress disrupts the balance between reactive oxygen species (ROS) and the antioxidant system in the body. During pregnancy, the physiological generation of ROS is involved in a variety of developmental processes ranging from oocyte maturation to luteolysis and embryo implantation. While abnormal overproduction of ROS disrupts these processes resulting in reproductive failure. In addition, excessive oxidative stress impairs maternal and placental functions and eventually results in fetal loss, IUGR, and gestational diabetes mellitus. Although some oxidative stress is inevitable during pregnancy, a balancing act between oxidant and antioxidant production is necessary at different stages of the pregnancy. The review aims to highlight the importance of maintaining oxidative and antioxidant balance throughout pregnancy. Furthermore, we highlight the role of oxidative stress in pregnancy-related diseases.

CoNaMad-Cohorte de Nacimiento de Madre de Dios/Madre de Dios Birth Cohort to Study Effects of in-utero Trace Metals Exposure in the Southern Peruvian Amazon

Background:

In-utero exposure to mercury and other trace metals pose a significant threat to child health and development, but exposures and health impacts in artisanal and small-scale gold mining (ASGM) environments are poorly defined.

Objectives:

We describe the CONAMAD study design, a prospective birth cohort consisting of multiparous women (18 and over) living in rural and peri-urban Peruvian Amazon communities exposed to ASGM.

Methods:

Pregnant women are enrolled from health posts across four zones of Madre de Dios, Peru. Data are collected at enrollment, childbirth, and (planned) 36-48 months. At enrollment, hair samples for mercury assessment, demographic and clinical data are obtained. At birth, we obtain venous and cord blood, placenta, hair, toenails, and saliva.

Findings:

Two hundred seventy mothers were enrolled at an average 20 weeks gestational age with no differences in maternal characteristics across zones. Two hundred fifteen mothers were successfully followed at birth. We obtained 214 maternal and cord blood samples, 211 maternal and 212 infant hair samples, 212 placenta samples, 210 infant saliva samples, and 214 infant dried blood spots. Data collected will allow for testing our primary hypotheses of maternal malnutrition modifying ratios of cord:maternal blood total mercury (tHg), cord blood:maternal hair tHg, and infant:maternal hair tHg, and whether chemical mixtures (Hg, Pb, Cd) have synergistic effects on infant neurodevelopment.

Conclusions:

CONAMAD is designed to collect and store samples for future processing and hypothesis testing associated with in-utero mercury exposure and child development. We have completed the exposure assessments and will conduct a follow-up of mothers to evaluate early child development outcomes, including developmental delay and growth. These data offer insights into disease mechanisms, exposure prevention, and policy guidance for countries where ASGM is prevalent.

First trimester mechanisms of gestational sac placental and foetal teratogenicity: a framework for birth cohort studies

BACKGROUND

The function of the gestational sac (GS) and the placenta in the closely related processes of embryogenesis and teratogenicity in the first trimester has been minimally described. The prevailing assumption is that direct teratogenic effects are mediated by the critical extraembryonic organ, the placenta, which either blocks or transfers exposures to the foetus. Placental transfer is a dominant mechanism, but there are other paradigms by which the placenta can mediate teratogenic effects. Knowledge of these paradigms and first trimester human developmental biology can be useful to the epidemiologist in the conduct of biomarker-based studies of both maternal and child health.

OBJECTIVE AND RATIONALE

Our aim is to provide a causal framework for modelling the teratogenic effects of first trimester exposures on child health outcomes mediated by the GS and placenta using biomarker data collected in the first trimester. We initially present first trimester human developmental biology for the sake of informing and strengthening epidemiologic approaches. We then propose analytic approaches of modelling placental mechanisms by way of causal diagrams using classical non-embryolethal teratogens (diethylstilboestrol [DES], folic acid deficiency and cytomegalovirus [CMV]) as illustrative examples. We extend this framework to two chronic exposures of particular current interest, phthalates and maternal adiposity.

SEARCH METHODS

Information on teratogens was identified by a non-systematic, narrative review. For each teratogen, we included papers that answered the five following questions: (i) why were these exposures declared teratogens? (ii) is there a consensus on biologic mechanism? (iii) is there reported evidence of a placental mechanism? (iv) can we construct a theoretical model of a placental mechanism? and (v) can this knowledge inform future work on measurement and modelling of placental-foetal teratogenesis? We prioritized literature specific to human development, the organogenesis window in the first trimester and non-embryolethal mechanisms.

OUTCOMES

As a result of our review of the literature on five exposures considered harmful in the first trimester, we developed four analytic strategies to address first trimester placental mechanisms in birth cohort studies: placental transfer and direct effects on the foetus (DES and maternal adiposity), indirect effects through targeted placental molecular pathways (DES and phthalates), pre-placental effects through disruptions in embryonic and extraembryonic tissue layer differentiation (folic acid deficiency), and multi-step mechanisms that involve maternal, placental and foetal immune function and inflammation (DES and CMV).

WIDER IMPLICATIONS

The significance of this review is to offer a causal approach to classify the large number of potentially harmful exposures in pregnancy when the exposure occurs in the first trimester. Our review will facilitate future research by advancing knowledge of the first trimester mechanisms necessary for researchers to effectively associate environmental exposures with child health outcomes.

Does the fibrinogen/albumin ratio predict the prognosis of pregnancies with abortus imminens?

OBJECTIVES

To investigate the fibrinogen/albumin ratio (FAR) of pregnant women with abortus imminens (AI) and its prognostic value for predicting spontaneous abortion.

METHODS

A total 102 early pregnancies, 52 had been diagnosed with AI and 50 ages and body mass index matched healthy control pregnant women were included in this prospective observational study conducted in the Research and Training Hospital, Balikesir University, Balikesir, Turkey between September 2019 and August 2020. Fibrinogen/albumin values were compared between AI and control group.

RESULTS

The rate of spontaneous abortion in AI pregnancies was 26.9% in our study population. Fibrinogen/albumin ratio levels were higher in AI pregnancies than in controls (p=0.0088). The regression analysis have shown that the increased FAR value (odds ratio [OR]: 7.3116 [95% CI: 1.3119 to 40.7507]; p=0.0232) was an independent marker for spontaneous abortion prediction in AI pregnancies.

CONCLUSION

Pregnancies with AI have increased levels of FAR compared to healthy pregnancies. Fibrinogen/albumin ratio is an independent marker for predicting spontaneous abortion.

Placentation in the Human and Higher Primates

Placentation in humans is precocious and highly invasive compared to other mammals. Implantation is interstitial, with the conceptus becoming completely embedded within the endometrium towards the end of the second week post-fertilization. Villi initially form over the entire surface of the chorionic sac, stimulated by histotrophic secretions from the endometrial glands. The secondary yolk sac never makes contact with the chorion, and a choriovitelline placenta is never established. However, recent morphological and transcriptomic analyses suggest that the yolk sac plays an important role in the uptake of nutrients from the coelomic fluid. Measurements performed in vivo demonstrate that early development takes place in a physiological, low-oxygen environment that protects against teratogenic free radicals and maintains stem cells in a multipotent state. The maternal arterial circulation to the placenta is only fully established around 10-12 weeks of gestation. By then, villi have regressed over the superficial, abembryonic pole, leaving the definitive discoid placenta, which is of the villous, hemochorial type. Remodeling of the maternal spiral arteries is essential to ensure a high-volume but low-velocity inflow into the mature placenta. Extravillous trophoblast cells migrate from anchoring villi and surround the arteries. Their interactions with maternal immune cells release cytokines and proteases that are key to remodeling, and a successful pregnancy.

Adaptations of the human placenta to hypoxia: opportunities for interventions in fetal growth restriction

BACKGROUND

The placenta is the functional interface between the mother and the fetus during pregnancy, and a critical determinant of fetal growth and life-long health. In the first trimester, it develops under a low-oxygen environment, which is essential for the conceptus who has little defense against reactive oxygen species produced during oxidative metabolism. However, failure of invasive trophoblasts to sufficiently remodel uterine arteries toward dilated vessels by the end of the first trimester can lead to reduced/intermittent blood flow, persistent hypoxia and oxidative stress in the placenta with consequences for fetal growth. Fetal growth restriction (FGR) is observed in ∼10% of pregnancies and is frequently seen in association with other pregnancy complications, such as preeclampsia (PE). FGR is one of the main challenges for obstetricians and pediatricians, as smaller fetuses have greater perinatal risks of morbidity and mortality and postnatal risks of neurodevelopmental and cardio-metabolic disorders.

OBJECTIVE AND RATIONALE

The aim of this review was to examine the importance of placental responses to changing oxygen environments during abnormal pregnancy in terms of cellular, molecular and functional changes in order to highlight new therapeutic pathways, and to pinpoint approaches aimed at enhancing oxygen supply and/or mitigating oxidative stress in the placenta as a mean of optimizing fetal growth.

SEARCH METHODS

An extensive online search of peer-reviewed articles using PubMed was performed with combinations of search terms including pregnancy, placenta, trophoblast, oxygen, hypoxia, high altitude, FGR and PE (last updated in May 2020).

OUTCOMES

Trophoblast differentiation and placental establishment are governed by oxygen availability/hypoxia in early pregnancy. The placental response to late gestational hypoxia includes changes in syncytialization, mitochondrial functions, endoplasmic reticulum stress, hormone production, nutrient handling and angiogenic factor secretion. The nature of these changes depends on the extent of hypoxia, with some responses appearing adaptive and others appearing detrimental to the placental support of fetal growth. Emerging approaches that aim to increase placental oxygen supply and/or reduce the impacts of excessive oxidative stress are promising for their potential to prevent/treat FGR.

WIDER IMPLICATIONS

There are many risks and challenges of intervening during pregnancy that must be considered. The establishment of human trophoblast stem cell lines and organoids will allow further mechanistic studies of the effects of hypoxia and may lead to advanced screening of drugs for use in pregnancies complicated by placental insufficiency/hypoxia. Since no treatments are currently available, a better understanding of placental adaptations to hypoxia would help to develop therapies or repurpose drugs to optimize placental function and fetal growth, with life-long benefits to human health.

Monochorionic twins with selective fetal growth restriction: insight from placental whole-transcriptome analysis

BACKGROUND

The underlying pathomechanism in placenta-related selective fetal growth restriction in monochorionic diamniotic twin pregnancy is not known.

OBJECTIVE

This study aimed to investigate any differences in placental transcriptomic profile between the selectively growth-restricted twins and the normally grown cotwins in monochorionic diamniotic twin pregnancies.

STUDY DESIGN

This was a prospective study of monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction. Placental biopsy specimens were obtained from the subjects in the delivery suite. The placental transcriptome of the selectively growth-restricted twin was compared with that of the normally grown cotwin. This study was divided into 2 stages: (1) gene discovery phase in which placental tissues from 5 monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction plus 2 control twin pregnancies underwent transcriptome profiling, and transcriptome profiling was carried out using whole-genome RNA sequencing; and (2) validation phase in which placental tissues from 13 monochorionic diamniotic twin pregnancies with selective fetal growth restriction underwent RNA and protein validation. RNA and protein expression levels of candidate genes were determined using quantitative real-time polymerase chain reaction and immunohistochemistry staining.

RESULTS

A total of 1429 transcripts were differentially expressed in the placentae of selectively growth-restricted twin pairs, where 610 were up-regulated and 819 were down-regulated. Endoplasmic reticulum lectin and mannose 6-phosphate receptor were consistently differentially up-regulated in all placentae of selectively growth-restricted twins. Quantitative real-time polymerase chain reaction and immunohistochemistry staining were used to validate the results (P<.05).

CONCLUSION

The expression of endoplasmic reticulum lectin and mannose 6-phosphate receptor, which are important for angiogenesis and fetal growth, was significantly increased in the placentae of selectively growth-restricted twin of a monochorionic twin pair.

Oxidative stress and mitochondrial dysfunction in early-onset and late-onset preeclampsia

Preeclampsia is a pregnancy-specific syndrome with multisystem involvement which leads to foetal, neonatal, and maternal morbidity and mortality. This syndrome is characterized by the onset of clinical signs and symptoms and delivery before (early-onset preeclampsia, eoPE), or after (late-onset preeclampsia, loPE), the 34 weeks of gestation. Preeclampsia is a mitochondrial disorder where its differential involvement in eoPE and loPE is unclear. Mitochondria regulate cell metabolism and are a significant source of reactive oxygen species (ROS). The syncytiotrophoblast in eoPE and loPE show altered mitochondrial structure and function resulting in ROS overproduction, oxidative stress, and cell damage and death. Mitochondrial dysfunction in eoPE may result from altered expression of several molecules, including dynamin-related protein 1 and mitofusins, compared with loPE where these factors are either reduced or unaltered. Equally, mitochondrial fusion/fission dynamics seem differentially modulated in eoPE and loPE. It is unclear whether the electron transport chain and oxidative phosphorylation are differentially altered in these two subgroups of preeclampsia. However, the activity of complex IV (cytochrome c oxidase) and the expression of essential proteins involved in the electron transport chain are reduced, leading to lower oxidative phosphorylation and mitochondrial respiration in the preeclamptic placenta. Interventional studies in patients with preeclampsia using the coenzyme Q₁₀, a key molecule in the electron transport chain, suggest that agents that increase the antioxidative capacity of the placenta may be protective against preeclampsia development. In this review, the mitochondrial dysfunction in both eoPE and loPE is summarized. Therapeutic approaches are discussed in the context of contributing to the understanding of mitochondrial dysfunction in eoPE and loPE.

Origin and function of the yolk sac in primate embryogenesis

Human embryogenesis is hallmarked by two phases of yolk sac development. The primate hypoblast gives rise to a transient primary yolk sac, which is rapidly superseded by a secondary yolk sac during gastrulation. Moreover, primate embryos form extraembryonic mesoderm prior to gastrulation, in contrast to mouse. The function of the primary yolk sac and the origin of extraembryonic mesoderm remain unclear. Here, we hypothesise that the hypoblast-derived primary yolk sac serves as a source for early extraembryonic mesoderm, which is supplemented with mesoderm from the gastrulating embryo. We discuss the intricate relationship between the yolk sac and the primate embryo and highlight the pivotal role of the yolk sac as a multifunctional hub for haematopoiesis, germ cell development and nutritional supply.

Protection of Lycopene against Embryonic Anomalies and Yolk Sac Placental Vasculogenic Disorders Induced by Nicotine Exposure

Identification of a new agent from natural products for the protection of embryonic anomalies is potentially valuable. To investigate the protective effect exerted by lycopene against nicotine-induced malformations, mouse embryos in embryonic day 8.5 with yolk sac placentas were cocultured with 1 mM nicotine and/or lycopene (1 × 10^-6, 1 × 10^-5 μM) for 48 h. The morphological defects and apoptotic cell deaths in the embryo and yolk sac placenta of the nicotine group were significantly increased. Exposure to nicotine resulted in reduced superoxide dismutase (SOD) activity and cytoplasmic SOD and cytoplasmic glutathione peroxidase mRNA levels, but increased lipid peroxidation level in embryos. Moreover, treatment with nicotine resulted in aggravated expressions of the mRNA or protein level of antiapoptotic (BCL2-associated X protein, B-cell lymphoma-extralarge, and caspase 3), anti-inflammatory (nuclear factor kappa-light-chain-enhancer of activated B cells and tumor necrosis factor-alpha), and vasculogenic (vascular endothelial growth factor-alpha, insulin-like growth factor-1, alpha smooth muscle actin, transforming growth factor-beta 1, and hypoxia inducible factor-1 alpha) factors in the embryo and yolk sac placenta. However, all the parameters were significantly improved by treatment with lycopene, as compared to the nicotine group. These findings indicate the potential of lycopene as a protective agent against embryonic anomalies and yolk sac vasculogenic and placenta-forming defects induced by nicotine through modulations of oxidative, apoptotic, vasculogenic, and inflammatory activities.

The role of mammalian foetal membranes in early embryogenesis: Lessons from marsupials

Across mammals, early embryonic development is supported by uterine secretions taken up through the yolk sac and other foetal membranes (histotrophic nutrition). The marsupial conceptus is enclosed in a shell coat for the first two-thirds of gestation and nutrients pass to the embryo through the shell and the avascular bilaminar yolk sac. At around the time of shell rupture, part of the yolk sac is trilaminar and supplied with blood vessels. It attaches to the uterus and forms a choriovitelline placenta. Rapid growth of the embryo ensues, still supported by histotrophe as well as exchange of oxygen and nutrients between maternal and foetal blood vessels (haemotrophic nutrition). Few marsupials have a chorioallantoic placenta and the highly altricial newborn is delivered after a short gestation. Eutherian embryos pass through a similar sequence before there is a fully functional chorioallantoic placenta. In most orders, there is transient yolk sac placentation, but even before this, nutrients are transferred through an avascular yolk sac. Yolk sac placentation does not occur in rodents or catarrhine primates. Early embryonic development in the mouse is nonetheless dependent on histotrophic nutrition. In the first trimester of human pregnancy, uterine glands open to the intervillous space and secretion products are taken up by the trophoblast. Transfer of nutrients to the early human embryo also involves the yolk sac, which floats free in the exocoelom. Marsupials can therefore inform us about the role of foetal membranes and histotrophic nutrition in early embryogenesis, knowledge that can translate to eutherians.

Soluble epoxide hydrolase in the human placenta throughout gestation

OBJECTIVE

To investigate the spatial and temporal changes of soluble epoxide hydrolase (sEH) in the human placenta throughout gestation and to study the effects of hypoxia-reoxygenation (HR) on the expression of sEH in villous explants in vitro.

MATERIALS AND METHODS

Placental samples were obtained from women of different gestation and grouped as early (8-12 weeks, n = 10), mid- (16-28 weeks, n = 6), and late gestation (38-39 weeks, n = 10) according to gestational age. Immunohistochemistry, western blot, and real-time quantitative PCR were used to assess the cellular distribution and temporal changes of sEH. Villous explant cultures were used to study the effect of HR (8 h at 2% oxygen, followed by 16 h at 8% oxygen, two cycles) on the expression of sEH.

RESULTS

Using a mouse monoclonal antibody against human sEH, immunoreactivity of sEH was observed mainly localized in the cytotrophoblasts and, to a lesser extent, the syncytiotrophoblast in the villous tissues throughout gestation. Compared to villous tissues of early gestation, the levels of sEH mRNA and protein were significantly increased in villous samples of mid- and late gestation. Furthermore, villous explants subjected to HR had significantly higher levels of sEH mRNA and protein compared to villous tissues kept at 8% oxygen throughout the experiment.

CONCLUSION

Our results indicate that sEH is likely to play an essential role in the development of human placenta and HR is a possible factor regulating the expression of sEH in the placenta.

Contributions of Drug Transporters to Blood-Placental Barrier

The placenta is the only organ linking two different individuals, mother and fetus, termed as blood-placental barrier. The functions of the blood-placental barrier are to regulate material transfer between the maternal and fetal circulation. The main functional units are the chorionic villi within which fetal blood is separated by only three or four cell layers (placental membrane) from maternal blood in the surrounding intervillous space. A series of drug transporters such as P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), multidrug resistance-associated proteins (MRP1, MRP2, MRP3, MRP4, and MRP5), organic anion-transporting polypeptides (OATP4A1, OATP1A2, OATP1B3, and OATP3A1), organic anion transporter 4 (OAT4), organic cation transporter 3 (OCT3), organic cation/carnitine transporters (OCTN1 and OCTN2), multidrug and toxin extrusion 1 (MATE1), and equilibrative nucleoside transporters (ENT1 and ENT2) have been demonstrated on the apical membrane of syncytiotrophoblast, some of which also expressed on the basolateral membrane of syncytiotrophoblast or fetal capillary endothelium. These transporters are involved in transport of most drugs in the placenta, in turn, affecting drug distribution in fetus. Moreover, expressions of these transporters in the placenta often vary along with the gestational ages and are also affected by pathophysiological factor. This chapter will mainly illustrate function and expression of these transporters in placentas, their contribution to drug distribution in fetus, and their clinical significance.

Uterine Glands: Developmental Biology and Functional Roles in Pregnancy

All mammalian uteri contain glands in the endometrium that develop only or primarily after birth. Gland development or adenogenesis in the postnatal uterus is intrinsically regulated by proliferation, cell-cell interactions, growth factors and their inhibitors, as well as transcription factors, including forkhead box A2 (FOXA2) and estrogen receptor α (ESR1). Extrinsic factors regulating adenogenesis originate from other organs, including the ovary, pituitary, and mammary gland. The infertility and recurrent pregnancy loss observed in uterine gland knockout sheep and mouse models support a primary role for secretions and products of the glands in pregnancy success. Recent studies in mice revealed that uterine glandular epithelia govern postimplantation pregnancy establishment through effects on stromal cell decidualization and placental development. In humans, uterine glands and, by inference, their secretions and products are hypothesized to be critical for blastocyst survival and implantation as well as embryo and placental development during the first trimester before the onset of fetal-maternal circulation. A variety of hormones and other factors from the ovary, placenta, and stromal cells impact secretory function of the uterine glands during pregnancy. This review summarizes new information related to the developmental biology of uterine glands and discusses novel perspectives on their functional roles in pregnancy establishment and success.

Pre-eclampsia: pathophysiology and clinical implications

Pre-eclampsia is a common disorder that particularly affects first pregnancies. The clinical presentation is highly variable but hypertension and proteinuria are usually seen. These systemic signs arise from soluble factors released from the placenta as a result of a response to stress of syncytiotrophoblast. There are two sub-types: early and late onset pre-eclampsia, with others almost certainly yet to be identified. Early onset pre-eclampsia arises owing to defective placentation, whilst late onset pre-eclampsia may center around interactions between normal senescence of the placenta and a maternal genetic predisposition to cardiovascular and metabolic disease. The causes, placental and maternal, vary among individuals. Recent research has focused on placental-uterine interactions in early pregnancy. The aim now is to translate these findings into new ways to predict, prevent, and treat pre-eclampsia.

Chronic gestational hypoxia accelerates ovarian aging and lowers ovarian reserve in next-generation adult rats

Chronic fetal hypoxia is a common complication observed in human pregnancy, impacting pregnancies across global contexts. Exposure to chronic intrauterine hypoxia has major short- and long-term consequences for offspring health. However, the impact of chronic gestational hypoxia on female reproductive system development is unknown. We aimed to understand the impact of exposure to chronic fetal hypoxia on the developing female reproductive system. Wistar rat dams underwent normoxia (21%) or hypoxia (13%) during pregnancy. Postnatally, all female offspring were maintained in normoxic conditions into early adulthood. Female rats exposed to chronic gestational hypoxia (13%) during their intrauterine development had decreased ovarian primordial follicular reserve compared to controls (P < 0.05). Adult females who had been exposed to chronic fetal hypoxia had significantly reduced somatic ovarian telomere length (P < 0.05) and reduced ovarian protein expression of KU70, a critical component of the DNA-activated protein kinase repair complex (P < 0.01). Gene expression of NADPH oxidase 2-mediated oxidative stress markers was increased (P < 0.05). Exposure to chronic hypoxia during fetal development leads to accelerated aging of the somatic ovary and decreased ovarian reserve in adulthood. Ovarian aging is highly sensitive to gestational hypoxia, with implications for future fertility in next-generation offspring of high-risk pregnancies.-Aiken, C. E., Tarry-Adkins, J. L., Spiroski, A.-M., Nuzzo, A. M., Ashmore, T. J., Rolfo, A., Sutherland, M. J., Camm, E. J., Giussani, D. A., Ozanne, S. E. Chronic gestational hypoxia accelerates ovarian aging and lowers ovarian reserve in next-generation adult rats.

Early development of the human placenta and pregnancy complications

An adequately sized placenta at a suitable site with appropriate depth and centripetal progression of implantation are the major factors for optimal fetal development. The cytotrophoblasts surround the blastocyst fuses at the site of the uterine attachment. This forms a second layer of multinucleated syncytiotrophoblasts that constitutes the inner epithelial boundary of the chorionic villous against the intervillous space. In a normal pregnancy, extravillous cytotrophoblasts (EVT) invade and obstruct the spiral arteries and remodel them. Vacuoles in the syncytial cell layer fuse and develop the intervillous space. The inner cell mass (embryoblast) gives rise to the umbilical cord and the mesenchyme in the chorionic villi. Vasculogenesis starts with the formation of hemangioblastic cords in this mesenchyme. The trophoblastic cell columns anchor the placenta. A variety of molecular pathways participate in the placentation process. Placental morphogenesis occurs mainly through complex cellular interactions between the chorionic villous and the extravillous cytotrophoblasts. The formation of the normal structure of the chorionic villi, syncytiotrophoblast layer and vasculature is essential for placental function, hormone production, and regulation of fetal growth. At each stage of placental development, genetic variants, exposure to infection, poor vascular function, oxidative stress, or failure of normal development can all lead to abnormal formation resulting in the clinical complications of pregnancy such as fetal growth disorders, neonatal neurologic abnormalities, placental adhesions, and inflammatory problems as well as maternal disease such as preeclampsia.

Role of Immune Distribution of Tissue Factor in the Development of Hemostasis during the First Trimester of Normal Pregnancy

Immunohistochemistry of tissue factor, vimentin, and cytokeratin-8 was studied in the medical abortion material at gestation week 5-10 in 20 healthy women. No expression of tissue factor was found in vimentin-positive decidual cells of the parietal endometrium. By contrast, intensive immunostaining of the TF/FVIIα complex was detected in the marginal layer of Rohr fibrinoid and less intense staining was found in vimentin-positive decidual cells adjacent to the walls of modified spiral arteries in the utero-placental region under conditions of invasion of the interstitial and intravascular cytotrophoblast (marker: cytokeratin-8). In the villi, tissue factor was expressed only in the fibrinoid lumps at sites of the syncytiotrophoblast defects. We demonstrated the formation of local hemostasis system in the uteroplacental region at weeks 5-8. This system creates optimal conditions for external thrombogenesis aimed at realization of the cytotrophoblast invasion and subsequent flow of arterial blood between the villi at the end of the first trimester.

Defining Physiological Normoxia for Improved Translation of Cell Physiology to Animal Models and Humans

The extensive oxygen gradient between the air we breathe (Po₂ ~21 kPa) and its ultimate distribution within mitochondria (as low as ~0.5-1 kPa) is testament to the efforts expended in limiting its inherent toxicity. It has long been recognized that cell culture undertaken under room air conditions falls short of replicating this protection in vitro. Despite this, difficulty in accurately determining the appropriate O₂ levels in which to culture cells, coupled with a lack of the technology to replicate and maintain a physiological O₂ environment in vitro, has hindered addressing this issue thus far. In this review, we aim to address the current understanding of tissue Po₂ distribution in vivo and summarize the attempts made to replicate these conditions in vitro. The state-of-the-art techniques employed to accurately determine O₂ levels, as well as the issues associated with reproducing physiological O₂ levels in vitro, are also critically reviewed. We aim to provide the framework for researchers to undertake cell culture under O₂ levels relevant to specific tissues and organs. We envisage that this review will facilitate a paradigm shift, enabling translation of findings under physiological conditions in vitro to disease pathology and the design of novel therapeutics.

A novel and compact review on the role of oxidative stress in female reproduction

In recent years, the study of oxidative stress (OS) has become increasingly popular. In particular, the role of OS on female fertility is very important and has been focused on closely. The occurrence of OS is due to the excessive production of reactive oxygen species (ROS). ROS are a double-edged sword; they not only play an important role as secondary messengers in many intracellular signaling cascades, but they also exert indispensable effects on pathological processes involving the female genital tract. ROS and antioxidants join in the regulation of reproductive processes in both animals and humans. Imbalances between pro-oxidants and antioxidants could lead to a number of female reproductive diseases. This review focuses on the mechanism of OS and a series of female reproductive processes, explaining the role of OS in female reproduction and female reproductive diseases caused by OS, including polycystic ovary syndrome (PCOS), endometriosis, preeclampsia and so on. Many signaling pathways involved in female reproduction, including the Keap1-Nrf2, NF-κB, FOXO and MAPK pathways, which are affected by OS, are described, providing new ideas for the mechanism of reproductive diseases.

Human coelomic fluid investigation: A MS-based analytical approach to prenatal screening

Coelomic fluid (CF) is the earliest dynamic and complex fluid of the gestational sac. CF contains maternal cells and proteins produced by embryonic cells, tissues and excretions. The biochemical composition of CF is modified throughout the first trimester of pregnancy and its protein profile reflects both physiological/pathological changes affecting the embryo and mother. Identification of variations in the balance of proteins might indicate particular types of pathologies, or ascertain specific genetic disorders. A platform utilizing protein enrichment procedures coupled with shotgun identification and iTRAQ differentiation provided the identification and quantitation of 88 unique embryonic proteins. It is relevant to note that chromosome X protein CXorf23 was found suggesting the embryo sex. Foetal sex was determined by Quantitative Fluorescent Polymerase Chain Reaction (QF-PCR) on coelomic cells, foetal tissues and maternal white blood cells, with a 100% concordance rate between iTRAQ-MS/MS and QF-PCR data. The functional associations among the identified proteins were investigated using STRING database. Open Targets Platform showed as significant the following therapeutic areas: nervous, respiratory, eye and head system disease.

Development of the Human Placenta and Fetal Heart: Synergic or Independent?

The placenta is the largest fetal organ, and toward the end of pregnancy the umbilical circulation receives at least 40% of the biventricular cardiac output. It is not surprising, therefore, that there are likely to be close haemodynamic links between the development of the placenta and the fetal heart. Development of the placenta is precocious, and in advance of that of the fetus. The placenta undergoes considerable remodeling at the end of the first trimester of pregnancy, and its vasculature is capable of adapting to environmental conditions and to variations in the blood supply received from the mother. There are two components to the placental membranes to consider, the secondary yolk sac and the chorioallantoic placenta. The yolk sac is the first of the extraembryonic membranes to be vascularized, and condensations in the mesenchyme at ~17 days post-conception (p.c.) give rise to endothelial and erythroid precursors. A network of blood vessels is established ~24 days p.c., with the vitelline vein draining through the region of the developing liver into the sinus venosus. Gestational sacs of early pregnancy failures often display aberrant development of the yolk sac, which is likely to be secondary to abnormal fetal development. Vasculogenesis occurs in the villous mesenchyme of the chorioallantoic placenta at a similarly early stage. Nucleated erythrocytes occupy the lumens of the placental capillaries and end-diastolic flow is absent in the umbilical arterial circulation throughout most of the first trimester, indicating a high resistance to blood flow. Resistance begins to fall in the umbilico-placental circulation around 12–14 weeks. During normal early pregnancy the placental capillary network is plastic, and considerable remodeling occurs in response to the local oxygen concentration, and in particular to oxidative stress. In pregnancies complicated by preeclampsia and/or fetal growth restriction, utero-placental malperfusion induces smooth muscle cells surrounding the placental arteries to dedifferentiate and adopt a proliferative phenotype. This change is associated with increased umbilical resistance measured by Doppler ultrasound, and is likely to exert a major effect on the developing heart through the afterload. Thus, both the umbilical and maternal placental circulations may impact on development of the heart.

Metabolic Pathways of the Warburg Effect in Health and Disease: Perspectives of Choice, Chain or Chance

Focus on the Warburg effect, initially descriptive of increased glycolysis in cancer cells, has served to illuminate mitochondrial function in many other pathologies. This review explores our current understanding of the Warburg effect’s role in cancer, diabetes and ageing. We highlight how it can be regulated through a chain of oncogenic events, as a chosen response to impaired glucose metabolism or by chance acquisition of genetic changes associated with ageing. Such chain, choice or chance perspectives can be extended to help understand neurodegeneration, such as Alzheimer’s disease, providing clues with scope for therapeutic intervention. It is anticipated that exploration of Warburg effect pathways in extreme conditions, such as deep space, will provide further insights crucial for comprehending complex metabolic diseases, a frontier for medicine that remains equally significant for humanity in space and on earth.

Placental Mechanics in the Zika-Microcephaly Relationship

How the Zika virus (ZIKV) accesses the embryo remains unknown. In this issue, Quicke et al. (2016) use an in vitro model of the human placenta to show that placental macrophages are more permissive to ZIKV infection than trophoblasts, which may be refractory to infection (Bayer et al., 2016).

RNA-seq reveals conservation of function among the yolk sacs of human, mouse, and chicken

The yolk sac is phylogenetically the oldest of the extraembryonic membranes. The human embryo retains a yolk sac, which goes through primary and secondary phases of development, but its importance is controversial. Although it is known to synthesize proteins, its transport functions are widely considered vestigial. Here, we report RNA-sequencing (RNA-seq) data for the human and murine yolk sacs and compare those data with data for the chicken. We also relate the human RNA-seq data to proteomic data for the coelomic fluid bathing the yolk sac. Conservation of transcriptomes across the species indicates that the human secondary yolk sac likely performs key functions early in development, particularly uptake and processing of macro- and micronutrients, many of which are found in coelomic fluid. More generally, our findings shed light on evolutionary mechanisms that give rise to complex structures such as the placenta. We identify genetic modules that are conserved across mammals and birds, suggesting these modules are part of the core amniote genetic repertoire and are the building blocks for both oviparous and viviparous reproductive modes. We propose that although a choriovitelline placenta is never established physically in the human, the placental villi, the exocoelomic cavity, and the secondary yolk sac function together as a physiological equivalent.

Oxidative stress, placental ageing-related pathologies and adverse pregnancy outcomes

Oxidative stress (OS), an imbalance between free radical generation and antioxidant defence, is recognized as a key factor in the pathogenesis of adverse pregnancy outcomes. Although OS is a common future of normal pregnancy, persistent, overwhelming OS leads to consumption and decline of antioxidants, affecting placental antioxidant capacity and reducing systems. The accumulation of OS causes damage to lipids, proteins and DNA in the placental tissue that induces a form of accelerated ageing. Premature ageing of the placenta is associated with placental insufficiency that prevents the organ meeting the needs of the foetus, and as a consequence, the viability of the foetus is compromised. This review summarizes the literature regarding the role of OS and premature placental ageing in the pathophysiology of pregnancy complications.

Choriovitelline placenta: prenatal sonographic imaging and clinical characteristics

OBJECTIVES

To describe the fetal sonographic characteristics, in-utero natural history and postnatal outcome of choriovitelline placenta, in which the fetal umbilical vein is replaced by the extra-embryonic vitelline circulation.

METHODS

This was a retrospective study of pregnancies examined during the period 2010-2014. Fetuses which presented with sonographic criteria of a downward caudal course of an enlarged vein from the umbilical annulus to the hepatic hilum were followed prospectively. Two-dimensional and three-dimensional color Doppler with high-definition flow were used in order to investigate the extra- and intrahepatic venous system. Ultrasound images and volumes were stored digitally, clinical data were obtained from patients' medical files and telephone interviews were conducted regarding the course of the pregnancy, perinatal data and developmental milestones.

RESULTS

Four cases were identified during the study period. The mean ± SD gestational age at diagnosis was 19.5 ± 4.3 (range, 13-23) weeks. The characteristic downward course of the persistent vitelline vein was associated with aneurysmal dilatation and anomalous anatomical configuration of the intrahepatic venous system. One case ended with antepartum death at 28 weeks. The mean gestational age at delivery was 34.6 (±5.0) weeks and the birth weight corresponded to the 57.2^nd (± 16.8 SD) centile. In two cases, a thrombotic mass was detected in the portal venous system after birth. One necessitated antithrombotic treatment for 6 months; in the other case, spontaneous resolution occurred 7 days after birth. In the three surviving infants, the persistent extrahepatic vitelline vein regressed gradually within 6 months after birth. Neurodevelopment was normal at follow-up aged 1 year and 7 months, 3 years and 6 months and 5 years and 5 months.

CONCLUSION

The main clinical importance of choriovitelline placentation derives from the possible formation of thrombus in the portal venous system. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Ischemia modified albumin in perinatology

Ischemia modified albumin is a novel marker of ischemia generated due to hypooxygenation and increased hydroxyl free radicals in low pH. The molecule has been licenced for clinical use as an early marker for acute coronary syndrome in cardiology. Since presence of ischemia might have serious and sometimes devastating effects in perinatology, various researches have evaluated its value in different clinical conditions. This narrative review aims to summarize the literature concerning the value of IMA in perinatology and guide for further research.

Correlation analysis between ultrasound findings and abnormal karyotypes in the embryos from early pregnancy loss after in vitro fertilization-embryo transfer

PURPOSE

The purpose of the study is to evaluate the correlation between ultrasound findings and abnormal karyotypes in early pregnancy losses (EPLs) after in vitro fertilization-embryo transfer (IVF-ET).

METHODS

This retrospective analysis assessed 2172 cases of EPL after IVF-ET occurring between January 2008 and December 2013. The cases were examined via transvaginal ultrasonography (TVS). Embryonic tissue karyotyping following miscarriage was performed using a comparative genomic hybridization (CGH) analysis with fluorescence in situ hybridization (FISH). The correlations between the ultrasound findings and the karyotypes were evaluated.

RESULTS

Six categories of ultrasound findings were observed: normal ultrasound, empty sac, yolk sac only, small gestational sac, small embryonic pole, and early symmetrical arrested growth. The overall rate of abnormal karyotypes was 44.9 % (976/2172), and the rate of abnormal karyotypes associated with a normal ultrasound, empty sac, yolk sac only, small gestational sac, small embryonic pole, and early symmetrical arrested growth was 49.5 % (218/440), 28.1 % (138/491), 43.4 % (197/454), 50.0 % (43/86), 49.8 % (155/311), and 57.7 % (225/390), respectively. Compared with the other groups, the prevalence of chromosomal abnormalities was significantly higher in the early symmetrical arrested growth group but was markedly lower in the empty sac group in all cases and when cases of 46,XX were excluded (p < 0.05). Trisomy 16 was the most common chromosomal abnormality in the yolk sac only, small embryonic pole and early symmetrical arrested growth groups. In the empty sac, small gestational sac and normal ultrasound groups, monosomy X was the most frequent abnormality.

CONCLUSIONS

Chromosomal anomalies may be associated with specific types of ultrasound findings in EPLs after IVF-ET.

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.

[The role of oxidative stress in placental-related diseases of pregnancy]

In normal pregnancies, the earliest stages of development take place in a low oxygen (O₂) environment. This physiological hypoxia of the early gestational sac protects the developing fetus against the deleterious and teratogenic effects of O₂free radicals. Oxidative stress is manifested at the maternal-fetal interface from early pregnancy onwards. In early pregnancy, a well-controlled oxidative stress plays a role in modulating placental development, functions and remodelling. Focal trophoblastic oxidative damage and progressive villous degeneration trigger the formation of the fetal membranes, which is an essential developmental step enabling vaginal delivery. Our data have demonstrated that the first trimester placenta in humans is histiotrophic and not haemochorial. The development and maintenance of a physiological O₂ gradient between the uterine and fetal circulations is also essential for placental functions, such as transport and hormonal synthesis. Pathological oxidative stress arises when the production of reactive O₂ species overwhelms the intrinsic anti-oxidant defences causing indiscriminate damage to biological molecules, leading to loss of function and cell death. We here review the role of oxidative stress in the pathophysiology of miscarriage, pre-eclampsia and fetal growth restriction.