Abnormalities of placenta implantation

A Narrative Review on the Pathophysiology of Preeclampsia

Preeclampsia (PE) is a multifactorial pregnancy disorder characterized by hypertension and proteinuria, posing significant risks to both maternal and fetal health. Despite extensive research, its complex pathophysiology remains incompletely understood. This narrative review aims to elucidate the intricate mechanisms contributing to PE, focusing on abnormal placentation, maternal systemic response, oxidative stress, inflammation, and genetic and epigenetic factors. This review synthesizes findings from recent studies, clinical trials, and meta-analyses, highlighting key molecular and cellular pathways involved in PE. The review integrates data on oxidative stress biomarkers, angiogenic factors, immune interactions, and mitochondrial dysfunction. PE is initiated by poor placentation due to inadequate trophoblast invasion and improper spiral artery remodeling, leading to placental hypoxia. This triggers the release of anti-angiogenic factors such as soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), causing widespread endothelial dysfunction and systemic inflammation. Oxidative stress, mitochondrial abnormalities, and immune dysregulation further exacerbate the condition. Genetic and epigenetic modifications, including polymorphisms in the Fms-like tyrosine kinase 1 (FLT1) gene and altered microRNA (miRNA) expression, play critical roles. Emerging therapeutic strategies targeting oxidative stress, inflammation, angiogenesis, and specific molecular pathways like the heme oxygenase-1/carbon monoxide (HO-1/CO) and cystathionine gamma-lyase/hydrogen sulfide (CSE/H2S) pathways show promise in mitigating preeclampsia's effects. PE is a complex disorder with multifactorial origins involving abnormal placentation, endothelial dysfunction, systemic inflammation, and oxidative stress. Despite advances in understanding its pathophysiology, effective prevention and treatment strategies remain limited. Continued research is essential to develop targeted therapies that can improve outcomes for both mothers and their babies.

Diagnostic significance of blood lymphocyte activation markers in pre-eclampsia

The adaptive and innate immune system is important in both initiating and preventing functional disorders during pregnancy, one of which is pre-eclampsia. The research aims to conduct the comparative quantification of selected subpopulations of peripheral blood immunoregulatory cells in pregnant women with pre-eclampsia in the third trimester. The marker receptors CD4, CD8, CD95, CD25, and CD27 and the marker antigen HLA-DR were considered. The screening was performed by flow cytometry with dual phenotyping using phycoerythrin- and fluorescein-isothiocyanate-labeled monoclonal antibodies. Data processing consisted in calculating a likelihood value to assess the statistical significance of the difference between the samples. A statistically significant decrease in the subpopulation titer of T and B lymphocytes with marker receptors CD4, CD8, and CD19 was found in pre-eclampsia patients. In the CD4 carrier T-lymphocyte population, there was an increased expression of the CD25/CD95 activation and apoptosis markers. In the CD8 T-killer population, a decreased representation of the CD27/CD25/CD95 markers of differentiation, activation, and apoptosis was deterministic. The expression pattern of the major histocompatibility complex antigen HLA-DR did not change significantly in normality and pathology. The titer of peripheral natural killer cells carrying the CD56 marker increased in patients with various degrees of disease severity, while the number of CD16 natural killer remained at the level of the control group. The research results suggest that a change in the ratio of the above receptors is a diagnostic indicator for pre-eclampsia.

Placenta Accreta Spectrum

Placenta accreta spectrum (PAS) is one of the most dangerous conditions in pregnancy and is increasing in frequency. The risk of life-threatening bleeding is present throughout pregnancy but is particularly high at the time of delivery. Although the exact cause is unknown, the result is clear: Severe PAS distorts the uterus and surrounding anatomy and transforms the pelvis into an extremely high-flow vascular state. Screening for risk factors and assessing placental location by antenatal ultrasonography are essential for timely diagnosis. Further evaluation and confirmation of PAS are best performed in referral centers with expertise in antenatal imaging and surgical management of PAS. In the United States, cesarean hysterectomy with the placenta left in situ after delivery of the fetus is the most common treatment for PAS, but even in experienced referral centers, this treatment is often morbid, resulting in prolonged surgery, intraoperative injury to the urinary tract, blood transfusion, and admission to the intensive care unit. Postsurgical complications include high rates of posttraumatic stress disorder, pelvic pain, decreased quality of life, and depression. Team-based, patient-centered, evidence-based care from diagnosis to full recovery is needed to optimally manage this potentially deadly disorder. In a field that has relied mainly on expert opinion, more research is needed to explore alternative treatments and adjunctive surgical approaches to reduce blood loss and postoperative complications.

Impact of Co-Occurrence of Obesity and SARS-CoV-2 Infection during Pregnancy on Placental Pathologies and Adverse Birth Outcomes: A Systematic Review and Narrative Synthesis

Obesity is a risk factor for severe COVID-19 disease during pregnancy. We hypothesized that the co-occurrence of high maternal body mass index (BMI) and gestational SARS-CoV-2 infection are detrimental to fetoplacental development. We conducted a systematic review following PRISMA/SWiM guidelines and 13 studies were eligible. In the case series studies (n = 7), the most frequent placental lesions reported in SARS-CoV-2(+) pregnancies with high maternal BMI were chronic inflammation (71.4%, 5/7 studies), fetal vascular malperfusion (FVM) (71.4%, 5/7 studies), maternal vascular malperfusion (MVM) (85.7%, 6/7 studies) and fibrinoids (100%, 7/7 studies). In the cohort studies (n = 4), three studies reported higher rates of chronic inflammation, MVM, FVM and fibrinoids in SARS-CoV-2(+) pregnancies with high maternal BMI (72%, n = 107/149; mean BMI of 30 kg/m2) compared to SARS-CoV-2(−) pregnancies with high BMI (7.4%, n = 10/135). In the fourth cohort study, common lesions observed in placentae from SARS-CoV-2(+) pregnancies with high BMI (n = 187 pregnancies; mean BMI of 30 kg/m2) were chronic inflammation (99%, 186/187), MVM (40%, n = 74/187) and FVM (26%, n = 48/187). BMI and SARS-CoV-2 infection had no effect on birth anthropometry. SARS-CoV-2 infection during pregnancy associates with increased prevalence of placental pathologies, and high BMI in these pregnancies could further affect fetoplacental trajectories.

Omics insights into extracellular vesicles in embryo implantation and their therapeutic utility

Implantation success relies on intricate interplay between the developing embryo and the maternal endometrium. Extracellular vesicles (EVs) represent an important player of this intercellular signalling through delivery of functional cargo (proteins and RNAs) that reprogram the target cells protein and RNA landscape. Functionally, the signalling reciprocity of endometrial and embryo EVs regulates the site of implantation, preimplantation embryo development and hatching, antioxidative activity, embryo attachment, trophoblast invasion, arterial remodelling, and immune tolerance. Omics technologies including mass spectrometry have been instrumental in dissecting EV cargo that regulate these processes as well as molecular changes in embryo and endometrium to facilitate implantation. This has also led to discovery of potential cargo in EVs in human uterine fluid (UF) and embryo spent media (ESM) of diagnostic and therapeutic value in implantation success, fertility, and pregnancy outcome. This review discusses the contribution of EVs in functional hallmarks of embryo implantation, and how the integration of various omics technologies is enabling design of EV-based diagnostic and therapeutic platforms in reproductive medicine.

Placental location and obstetrical-neonatal outcomes: A retrospective study

OBJECTIVE

To explore the potential association of lateral placentation with pregnancy outcome.

METHODS

The database of a tertiary medical center was searched for women who gave birth to a singleton neonate from 2012 to 2020 for whom placental location was documented during antepartum sonographic examination. Clinical data were compared between patients with a central (anterior/posterior/fundal) or lateral placenta using standard statistics. The primary outcome measure was neonatal birthweight, and secondary outcome measures were pregnancy complications and mode of delivery.

RESULTS

The cohort included 12 306 women: 11 608 (94%) with a central placenta and 698 (5.6%) with a lateral placenta. The lateral placenta group had higher rates (P < 0.05) of prior and current cesarean delivery, assisted delivery, and preterm birth. On multivariate regression analyses, placental location (adjusted odds ratio [aOR], 1.36; 95% confidence interval [CI], 1.11-1.66) and maternal age (aOR, 1.02; 95% CI, 1.01-1.03) were associated with risk of preterm birth. Lateral placenta (aOR, 1.22; 95% CI, 1.02-1.47), maternal age (aOR, 1.07; 95% CI, 1.06-1.08), parity (aOR, 0.32; 95% CI, 0.28-0.35), and prior cesarean delivery (aOR, 12.00; 95% CI, 10.60-13.60) were associated with risk of current cesarean delivery.

CONCLUSION

The findings suggest that lateral placentation may pose a risk of preterm birth and cesarean delivery compared with central placentation.

Placenta Accreta Spectrum: Correlation between FIGO Clinical Classification and Histopathologic Findings

OBJECTIVE

Placenta accreta spectrum (PAS) covers a wide spectrum of placental adherence/invasion with varied clinical significance. Histopathologic examination is considered the confirmatory gold standard, but is only obtained sometime after definitive treatment. The International Federation of Gynecology and Obstetrics (FIGO) has published a new clinical classification that can be assigned at delivery, and we aimed to investigate the association between this new FIGO classification and histopathology and also to assess its correlation with maternal outcomes.

STUDY DESIGN

We studied a retrospective cohort of 185 patients with histopathologically proven PAS managed at our referral center between September 2012 and January 2019. Two experienced surgeons retrospectively reviewed charts and assigned the FIGO grading based on findings reported at delivery. A third experienced reviewer adjudicated to determine the classification used for final analysis. Categorical outcomes were compared with the use of chi-squared and the Fisher exact test, as appropriate. A multivariate model was designed to adjust outcomes in different FIGO groups for the involvement of a formal multidisciplinary management team.

RESULTS

Among 185 patients, there were 41 (22%) placenta accreta, 44 (24%) placenta increta, and 100 (54%) placenta percreta on histopathology. The inter-rater reliability was found to be substantial with Kappa = 0.661 (p < 0.001), and 95% confidence interval (CI): 0.449-0.872. There was a significant association between all histopathology groupings and the FIGO clinical classification (p < 0.001). However, we found no association between FIGO classifications and maternal complications.

CONCLUSION

The new FIGO clinical classification is strongly associated with histopathologic findings. A better understanding of the depth and extent of invasion as afforded by the clinical classification system will help standardize reporting and future research.

KEY POINTS

· PAS includes a wide spectrum of placental invasion with varied clinical significance.. · Histopathological examination is considered the confirmatory gold standard.. · The new FIGO clinical classification is strongly associated with histopathologic findings..

A retrospective study of estrogen in the pretreatment for medical management of early pregnancy loss and the inference from intrauterine adhesion

Background

Estrogen has been usually used in clinic for medical pretreatment of early pregnancy loss. There was little reported the effect of estrogen combined with prostaglandin analogs in the medical management of early pregnancy loss. This retrospective study aimed to evaluate the efficacy of estrogen pretreatment for medical management of early pregnancy loss and explore the confounding factor of intrauterine adhesion (IUA) on the outcome of medical management.

Methods

A total of 226 early pregnancy loss patients who received pretreatment with estradiol valerate and/or mifepristone, followed by carboprost methylate suppositories (study groups), or carboprost methylate suppositories alone (control group) in a regional central institution from March 2020 to February 2021 were retrospectively studied. All patients were evaluated by hysteroscopy 6 h after carboprost methylate suppositories use to assess whether the gestational sac was complete expulsion and assess the morphology of uterine cavity.

Results

The complete expulsion rate was 56.94% in the mifepristone and estradiol valerate-pretreatment group, 20.69% in the estradiol valerate-pretreatment group, 62.5% in the mifepristone-pretreatment group, and 12.5% in the control group. Compared with the control group, pretreatment with estradiol valerate did not increase the complete expulsion rate significantly (P = 0.297), pretreatment with mifepristone increased the complete expulsion rate significantly (P < 0.001). Pretreatment with mifepristone combined with estradiol valerate did not increase the complete expulsion rate significantly comparing with pretreatment with mifepristone (P = 0.222). The data of IUA showed that the complete expulsion rate in patients with IUA was lower than that in those patients without IUA (P < 0.001).

Conclusions

Pretreatment with estrogen was not a sensible substitute for mifepristone in the medical management of early pregnancy loss. Mifepristone followed by carboprost methylate suppositories was likelihood of the ideal medical scheme in early pregnancy loss. IUA decreased the complete expulsion rate of medical management, it is cautious about medical management for early pregnancy loss with risk of IUA.

Trial Registration Number: ChiCTR2100046503. Date of registration (retrospectively registered): May 18, 2021. Trial registration website: http://www.chictr.org.cn/.

Clinical Utility of the Prenatal Ultrasound Score of the Placenta Combined with Magnetic Resonance Imaging in Diagnosis of Placenta Accreta during the Second and Third Trimester of Pregnancy

Objective. The aim is to explore the clinical utility of the prenatal ultrasound score of the placenta combined with magnetic resonance imaging (MRI) in diagnosis of placenta accreta during the second and third trimester of pregnancy. Materials and Methods. A total of 108 pregnant women with suspected placenta accreta treated in Wuhan Hankou Hospital and Yantaishan Hospital of Yantai from January 2019 to January 2022 were retrospectively analyzed, the enrolled pregnant women received MRI examination because of suspected results of ultrasonic diagnosis, and by taking pathologic findings as the gold standard, the diagnostic efficacy of the ultrasound score, MRI, and their combination to placenta accreta during the second and third trimester of pregnancy was analyzed, and the diagnostic sensitivity, specificity, the positive predictive value, and the negative predictive value of these diagnostic modalities were evaluated. Results. Among 108 patients with suspected placenta accreta, 75 with pathologically confirmed placenta accreta were included in the accreta group, and 33 without placenta accreta were included in the non-accreta group; no statistical between-group differences in the patients’ age, gestational weeks, educational degree, and other general data were observed ( $P>0.05$ ), but the history of cesarean section, history of induced abortion, and incidence rate of placenta praevia were significantly higher in the accreta group than in the non-accreta group ( $P<0.05$ ); the ultrasound score was significantly higher in the accreta group than in the non-accreta group ( $P<0.05$ ); the incidence rates of signs of “placental heterogeneity” and “bulge of lower segment of the uterus and local thickening of the placenta” were obviously higher in the accreta group than in the non-accreta group ( $P<0.05$ ); according to the comparison with pathologic findings, the accuracy rate, sensitivity, specificity, the positive predictive value, and the negative predictive value of combined diagnosis were significantly higher than those of single application of the ultrasound score and MRI diagnosis ( $P<0.05$ ); and ROC analysis found that the area under the curve of combined diagnosis was obviously larger than that of the ultrasound score and MRI diagnosis ( $P<0.05$ ). Conclusion. A combining prenatal ultrasound score of the placenta with MRI plays an important role in the diagnosis of placenta accreta during the second and third trimester of pregnancy, which can further improve the diagnostic accuracy rate of placenta accreta and provide significant guidance in preventing high-risk complications during the perinatal period.

Transcriptomic analysis reveals differential gene expression, alternative splicing, and novel exons during mouse trophoblast stem cell differentiation

BACKGROUND

Differentiation of mouse trophoblast stem cells (TSCs) to trophoblast giant cells (TGCs) has been widely used as a model system to study placental development and function. While several differentially expressed genes, including regulators of TSC differentiation, have been identified, a comprehensive analysis of the global expression of genes and splice variants in the two cell types has not been reported.

RESULTS

Here, we report ~ 7800 differentially expressed genes in TGCs compared to TSCs which include regulators of the cell cycle, apoptosis, cytoskeleton, cell mobility, embryo implantation, metabolism, and various signaling pathways. We show that several mitotic proteins, including Aurora A kinase, were downregulated in TGCs and that the activity of Aurora A kinase is required for the maintenance of TSCs. We also identify hitherto undiscovered, cell-type specific alternative splicing events in 31 genes in the two cell types. Finally, we also report 19 novel exons in 12 genes which are expressed in both TSCs and TGCs.

CONCLUSIONS

Overall, our results uncover several potential regulators of TSC differentiation and TGC function, thereby providing a valuable resource for developmental and molecular biologists interested in the study of stem cell differentiation and embryonic development.

Development of placental abnormalities in location and anatomy

Low‐lying placentas, placenta previa and abnormally invasive placentas are the most frequently occurring placental abnormalities in location and anatomy. These conditions can have serious consequences for mother and fetus mainly due to excessive blood loss before, during or after delivery. The incidence of such abnormalities is increasing, but treatment options and preventive strategies are limited. Therefore, it is crucial to understand the etiology of placental abnormalities in location and anatomy. Placental formation already starts at implantation and therefore disorders during implantation may cause these abnormalities. Understanding of the normal placental structure and development is essential to comprehend the etiology of placental abnormalities in location and anatomy, to diagnose the affected women and to guide future research for treatment and preventive strategies. We reviewed the literature on the structure and development of the normal placenta and the placental development resulting in low‐lying placentas, placenta previa and abnormally invasive placentas.

Immune and Apoptosis Mechanisms Regulating Placental Development and Vascularization in Preeclampsia

Preeclampsia is the most severe type of hypertensive disorder of pregnancy, affecting one in 10 pregnancies worldwide and increasing significantly maternal and neonatal morbidity and mortality. Women developing preeclampsia display an array of symptoms encompassing uncontrolled hypertension and proteinuria, with neurological symptoms including seizures at the end of pregnancy. The main causes of preeclampsia are still unknown. However, abnormal placentation and placenta vascularization seem to be common features in preeclampsia, also leading to fetal growth restriction mainly due to reduced placental blood flow and chronic hypoxia. An over activation of maternal immunity cells against the trophoblasts, the main cells forming the placenta, has been recently shown as an important mechanism triggering trophoblast apoptosis and death. This response will further disrupt the remodeling of maternal uterine arteries, in a first stage, and the formation of new placental vessels in a later stage. A consequent chronic hypoxia stress will further contribute to increase placental stress and exacerbate systemic circulatory changes in the mother. The molecular mechanisms driving these processes of apoptosis and anti-angiogenesis are also not well-understood. In this review, we group main evidences suggesting potential targets and molecules that should be better investigated in preeclampsia. This knowledge will contribute to improve therapies targeting a better placenta formation, having a positive impact on maternal disease prevention and on fetal development.

Comparison between abdominal ultrasound and nuclear magnetic resonance imaging detection of placenta accreta in the second and third trimester of pregnancy

This study is to determine accuracy of abdominal ultrasound and nuclear magnetic resonance imaging (MRI) for placenta accreta in the second and third trimester of pregnancy and to define the most relevant features of abdominal ultrasound and MRI for placenta accreta prediction.Between September 2012 and September 2018, 245 high risk of placenta accreta in the second trimester of pregnancy were prenatal diagnosed by abdominal ultrasound and MRI and they were followed up until the end of pregnancy.Forty-six patients at the second trimester of pregnancy and 40 patients at the third trimester of pregnancy were confirmed as placenta accreta. For the second and third trimester of pregnancy, the sensitivity (Se), specificity (Sp), positive and negative predictive value (PPV and NPV) of abdominal ultrasound were 95.65% versus 97.50%, 91.78% versus 90.70%, 88% versus 83%, and 97% versus 99%, respectively, while the Se, Sp, PPV, and NPV of MRI were 89.13% versus 92.50%, 87.67% versus 8721%, 82% versus 77%, and 93% versus 96%, respectively. Five features having significant statistical differences between normal placentation women and placenta accreta patients in second or third trimester of pregnancy, including loss of the normal retroplacental clear space, thinning or disappearance of the myometrium, increased vascularization at the uterine serosa-bladder wall interface, and vascularization perpendicular to the uterine wall on abdominal ultrasound, and uterine bulging and dark intraplacental bands on MRI.Abdominal ultrasound and MRI for placenta accreta in the second and third trimester of pregnancy could provide meaningful imaging evidences.

Placental location and pregnancy outcomes in nulliparous women: A population-based cohort study

INTRODUCTION

The impact of placenta previa on pregnancy, delivery and infant outcomes has been extensively studied. However, less is known about the possible association of placental location other than previa with pregnancy outcomes. The aim of this study was to investigate if placental location other than previa is associated with adverse pregnancy, delivery and infant outcomes.

MATERIAL AND METHODS

This is a population-based cohort study, with data from the regional population-based Stockholm-Gotland Obstetric Cohort, Sweden, from 2008 to 2014. The study population included 74 087 nulliparous women with singleton pregnancies resulting in live-born infants, with information about placental location from the second-trimester ultrasound screening. The association between placental location (fundal, lateral, anterior or posterior) and pregnancy outcomes was estimated using logistic regression analysis. Odds ratios (OR) with 95% confidence intervals (95% CI) were calculated, and adjustments were made for maternal age, height, country of birth, smoking in early pregnancy, sex of the infant and in vitro fertilization. Main outcome measures were pregnancy, delivery and infant outcomes.

RESULTS

Compared with posterior placental location, fundal and lateral placental locations were associated with a number of adverse pregnancy outcomes, the most important being: very preterm birth (<32 weeks of gestation) (adjusted OR [aOR] 1.78, 95% CI 1.18-2.63 and aOR 2.12, 95% CI 1.39-2.25, respectively), moderate preterm birth (32-36 weeks of gestation) (aOR 1.23, 95% CI 1.001-1.51 and aOR 1.62, 95% CI 1.32-2.00, respectively), small-for-gestational-age birth (aOR 1.67, 95% CI 1.34-2.07 and aOR 1.77, 95% CI 1.39-2.25, respectively) and manual removal of the placenta in vaginal births (aOR 3.27, 95% CI 2.68-3.99 and aOR 3.27, 95% CI 2.60-4.10, respectively). Additionally, lateral placental location was associated with preeclampsia (aOR 1.30, 95% CI 1.03-1.65) and severe postpartum hemorrhage (aOR 1.42, 95% CI 1.27-1.82).

CONCLUSIONS

Compared with posterior placental location, fundal and lateral placental locations are associated with a number of adverse pregnancy, delivery and infant outcomes.