Imaging of Placenta Accreta Spectrum

Customizing EV-CATCHER to Purify Placental Extracellular Vesicles from Maternal Plasma to Detect Placental Pathologies

Placenta Accreta Spectrum (PAS) is a life-threatening condition in which placental trophoblastic cells abnormally invade the uterus, often up to the uterine serosa and, in extreme cases, tissues beyond the uterine wall. Currently, there is no clinical assay for the non-invasive detection of PAS, and only ultrasound and MRI can be used for its diagnosis. Considering the subjectivity of visual assessment, the detection of PAS necessitates a high degree of expertise and, in some instances, can lead to its misdiagnosis. In clinical practice, up to 50% of pregnancies with PAS remain undiagnosed until delivery, and it is associated with increased risk of morbidity/mortality. Although many studies have evaluated the potential of fetal biomarkers circulating in maternal blood, very few studies have evaluated the potential of circulating placental extracellular vesicles (EVs) and their miRNA contents for molecular detection of PAS. Thus, to purify placental EVs from maternal blood, we customized our robust ultra-sensitive immuno-purification assay, termed EV-CATCHER, with a monoclonal antibody targeting the membrane Placental Alkaline Phosphatase (PLAP) protein, which is unique to the placenta and present on the surface of placental EVs. Then, as a pilot evaluation, we compared the miRNA expression profiles of placental EVs purified from the maternal plasma of women diagnosed with placenta previa (controls, n = 16); placenta lying low in uterus but not invasive) to those of placental EVs purified from the plasma of women with placenta percreta (cases, n = 16), PAS with the highest level of invasiveness. Our analyses reveal that miRNA profiling of PLAP+ EVs purified from maternal plasma identified 40 differentially expressed miRNAs when comparing these two placental pathologies. Preliminary miRNA pathway enrichment and gene ontology analysis of the top 14 upregulated and top nine downregulated miRNAs in PLAP+ EVs, purified from the plasma of women diagnosed with placenta percreta versus those diagnosed with placenta previa, suggests a potential role in control of cellular invasion and motility that will require further investigation.

Sensitivity of antenatal ultrasound in diagnosing posterior placenta accreta spectrum disorders

OBJECTIVES

Optimal management of placenta accreta spectrum (PAS) requires antenatal diagnosis. We sought to evaluate the sensitivity of ultrasound findings suggestive of PAS in detecting posterior PAS.

METHODS

Cohort study of patients with posterior placentation and pathology-confirmed PAS from 2011 to 2020 at a tertiary center. Patients were excluded if ultrasound images were unavailable. Ultrasounds were reviewed for presence of lacunae, hypervascularity, myometrial thinning, loss of the hypoechoic zone, bridging vessels, abnormal uterine serosa-bladder interface, placental bulge, placental extension into/beyond the myometrium, and an exophytic mass. Risk factors, postpartum outcomes, and ultrasound findings were compared by antepartum suspicion for PAS. Sensitivity was calculated for each ultrasound finding.

RESULTS

Thirty-three patients were included. PAS was not suspected antenatally in 70 % (23/33). Patients with unsuspected PAS were more likely to be non-Hispanic, have in vitro fertilization, no prior Cesarean deliveries, no placenta previa, and delivered later in gestation. Depth of invasion and estimated blood loss were less for unsuspected PAS, but there was no difference in hysterectomy between groups. Ultrasound findings were less frequently seen in those who were not suspected antenatally: lacunae 17.4 vs. 100 % (p<0.001), hypervascularity 8.7 vs. 80 % (p<0.001), myometrial thinning 4.4 vs. 70 % (p<0.001), and placental bridging vessels 0 vs. 60 % (p<0.001). There was poor sensitivity (0-42.4 %) for all findings.

CONCLUSIONS

Posterior PAS is less likely to be detected antenatally due to a lower sensitivity of typical ultrasound findings in the setting of a posterior placenta. Further studies are needed to better identify reliable markers of posterior PAS.

Value of early pregnancy ultrasound combined with ultrasound score in the evaluation of placenta accreta in scar uterus: A retrospective cohort study

The objective of this study is to investigate the value of early pregnancy ultrasound combined with ultrasound score (USS) for the evaluation of placenta accreta (PA) in scar uteri. Thirty cases of PA in scar uteri diagnosed by ultrasound at our hospital between June 2021 and June 2022 were selected retrospectively (observation group). In addition, 30 patients had placenta attached to the anterior wall of the uterus and covered the internal orifice of the cervix; however, no PA was selected in the same period (control group). The results of surgical pathology and ultrasound examination in the first trimester of pregnancy (11-14 weeks of pregnancy, fetal top hip length 4.5-8.4 cm) were analyzed. Ultrasonic image characteristics of the 2 groups were scored using an ultrasonic scoring scale. The ultrasonic signs and ultrasonic scores of the 2 groups were analyzed. The diagnostic value of ultrasound and USS for PA in the scarred uterus alone and in combination was analyzed based on the gold standard of surgical and pathological results. The rich blood flow signal at the junction of the uterine serosa and bladder, the rate of blood flow in the cavity of the placental parenchyma, the thinning rate of the myometrium after placenta, and the abnormal rate of the low echo area after placenta in the observation group were significantly higher than those in the control group (P < .05). The USS of the observation group was significantly higher than that of the control group (P < .05). The sensitivity (93.33%) and accuracy (95.00%) of the combined examinations were significantly higher than those of ultrasound (70.00% and 83.33%, respectively) (P < .05). The sensitivity and accuracy of combined examination were slightly higher than those of USS examination (83.33% and 90.00%), but the difference was not statistically significant (P > .05). There was no significant difference between the specificity of combined examination (93.33%) and ultrasound (96.67%) and USS (96.67%) (P > .05). Early pregnancy ultrasound and USS evaluation have high application value in the diagnosis and evaluation of early scar uterine PA. The combination of the 2 methods can further improve the sensitivity and accuracy of diagnosis.

Gynaecological Causes of Acute Pelvic Pain: Common and Not-So-Common Imaging Findings

In female patients, acute pelvic pain can be caused by gynaecological, gastrointestinal, and urinary tract pathologies. Due to the variety of diagnostic possibilities, the correct assessment of these patients may be challenging. The most frequent gynaecological causes of acute pelvic pain in non-pregnant women are pelvic inflammatory disease, ruptured ovarian cysts, ovarian torsion, and degeneration or torsion of uterine leiomyomas. On the other hand, spontaneous abortion, ectopic pregnancy, and placental disorders are the most frequent gynaecological entities to cause acute pelvic pain in pregnant patients. Ultrasound (US) is usually the first-line diagnostic technique because of its sensitivity across most common aetiologies and its lack of radiation exposure. Computed tomography (CT) may be performed if ultrasound findings are equivocal or if a gynaecologic disease is not initially suspected. Magnetic resonance imaging (MRI) is an extremely useful second-line technique for further characterisation after US or CT. This pictorial review aims to review the spectrum of gynaecological entities that may manifest as acute pelvic pain in the emergency department and to describe the imaging findings of these gynaecological conditions obtained with different imaging techniques.

Animal models of the placenta accreta spectrum: current status and further perspectives

Placenta accreta spectrum disorder (PAS) is a kind of disease of placentation defined as abnormal trophoblast invasion of part or all of the placenta into the myometrium, even penetrating the uterus. Decidual deficiency, abnormal vascular remodeling in the maternal-fetal interface, and excessive invasion by extravillous trophoblast (EVT) cells contribute to its onset. However, the mechanisms and signaling pathways underlying such phenotypes are not fully understood, partly due to the lack of suitable experimental animal models. Appropriate animal models will facilitate the comprehensive and systematic elucidation of the pathogenesis of PAS. Due to the remarkably similar functional placental villous units and hemochorial placentation to humans, the current animal models of PAS are based on mice. There are various mouse models induced by uterine surgery to simulate different phenotypes of PAS, such as excessive invasion of EVT or immune disturbance at the maternal-fetal interface, which could define the pathological mechanism of PAS from the perspective of the "soil." Additionally, genetically modified mouse models could be used to study PAS, which is helpful to exploring the pathogenesis of PAS from the perspectives of both "soil" and "seed," respectively. This review details early placental development in mice, with a focus on the approaches of PAS modeling. Additionally, the strengths, limitations and the applicability of each strategy and further perspectives are summarized to provide the theoretical foundation for researchers to select appropriate animal models for various research purposes. This will help better determine the pathogenesis of PAS and even promote possible therapy.

Ultrasonographic Prediction of Placental Invasion in Placenta Previa by Placenta Accreta Index

This study aimed to investigate the diagnostic accuracy of the placenta accreta index (PAI) for predicting placenta accreta spectrum (PAS) in women with placenta previa. We analyzed 33 pregnancies with placenta previa at Keio University Hospital. The PAI was assessed in the early third trimester, and PAS was diagnosed histologically or clinically defined as retained placenta after manual removal attempts. The PAI and incidence of PAS were analyzed. Ten women (30%) were diagnosed with PAS and had higher volumes of perioperative bleeding (p = 0.016), higher rate of requiring uterine artery embolization (p = 0.005), and peripartum hysterectomy (p = 0.0002) than women without PAS. A PAI > 2 was the most useful cut-off point for predicting PAS and was more sensitive than prediction values using traditional evaluation (history of cesarean section and placental location). Post-hoc analysis revealed a higher rate of previous history of cesarean delivery (30% vs. 4.4%, p = 0.038), severe placental lacunae (≥grade2) (70% vs. 8.7%, p = 0.0003), thin myometrial thickness (90% vs. 22%, p = 0.0003), anterior placenta (100% vs. 30%, p = 0.0002), and presence of bridging vessels (30% vs. 0%, p = 0.0059) in PAS women. PAI could help predict the outcomes of women with placenta previa with and without a history of cesarean delivery to reduce PAS-induced perinatal complications.

Placental and Umbilical Cord Anomalies Diagnosed by Two- and Three-Dimensional Ultrasound

The aim of this review is to present a wide spectrum of placental and umbilical cord pathologies affecting the pregnancy. Placental and umbilical cord anomalies are highly associated with high-risk pregnancies and may jeopardize fetal well-being in utero as well as causing a predisposition towards poor perinatal outcome with increased fetal and neonatal mortality and morbidity. The permanent, computerized perinatology databases of different international centers have been searched and investigated to fulfil the aim of this manuscript. An extended gallery of prenatal imaging with autopsy correlation in specific cases will help to provide readers with a useful iconographic tool and will assist with the understanding and definition of this critical obstetrical and perinatological issue.

Ultrasound-based nomogram for postpartum hemorrhage prediction in pernicious placenta previa

Background: Pernicious placenta previa (PPP) is one of the most dangerous complications in pregnancy after cesarean section, with high perinatal mortality. This study aimed to develop a nomogram to predict postpartum hemorrhage in patients with PPP.

Methods: A total of 246 patients with confirmed PPP at Shengjing Hospital of China Medical University from January 2018 to December 2021 were included. Patients were divided into to two cohorts depending on a postpartum blood loss of > 1000 ml (n = 146) or ≤ 1000 ml (n = 100). Lasso regression analysis was performed on the risk factors screened by univariate analysis to screen out the final risk factors affecting postpartum hemorrhage. Based on the final risk factors, a Nomogram prediction model with excellent performance was constructed using Logistic regression. A nomogram was constructed with further screening of the selected risk factors of postpartum hemorrhage in PPP. A second nomogram based only on the total ultrasonic risk score was constructed. Decision curve analysis (DCA) was used to evaluate the clinical efficacy of the nomograms.

Results: Older age, larger gestational age, larger neonatal birth weight, presence of gestational diabetes mellitus, larger amniotic fluid index, absence of gestational bleeding, and higher ultrasonic risk single score were selected to establish a nomogram for postpartum hemorrhage in PPP. The area under the curve of the nomogram constructed by Lasso regression analysis was higher than that of the ultrasonic total score alone (0.887 vs. 0.833). Additionally, DCA indicated better clinical efficacy in the former nomogram than in the later nomogram. Furthermore, internal verification of the nomogram constructed by Lasso regression analysis showed good agreement between predicted and actual values.

Conclusion: A nomogram for postpartum hemorrhage in PPP was developed and validated to assist clinicians in evaluating postpartum hemorrhage. This nomogram was more accurate than using the ultrasonic score alone.

Doppler evaluation of normal and abnormal placenta

Doppler techniques are needed for the evaluation of the intraplacental circulation and can be of great value in the diagnosis of placental anomalies. Highly sensitive Doppler techniques can differentiate between the maternal (spiral arteries) and fetal (intraplacental branches of the umbilical artery) components of the placental circulation and assist in the evaluation of the placental functional units. A reduced number of placental functional units can be associated with obstetric complications, such as fetal growth restriction. Doppler techniques can also provide information on decidual vessels and blood movement. Abnormal decidual circulation increases the risk of placenta accreta. Doppler evaluation of the placenta greatly contributes to the diagnosis and clinical management of placenta accreta, vasa previa, placental infarcts, placental infarction hematoma, maternal floor infarction, massive perivillous fibrin deposition and placental tumors. However, it has a limited role in the diagnosis and clinical management of placental abruption, placental hematomas, placental mesenchymal dysplasia and mapping of placental anastomoses in monochorionic twin pregnancies. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

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.

USMRI Features and Clinical Data-Based Model for Predicting the Degree of Placenta Accreta Spectrum Disorders and Developing Prediction Models

AIM

This study aimed to investigate the ability of ultrasound/magnetic resonance imaging (MRI) signature and clinical data-based model for preoperatively predicting the degree of placenta accreta spectrum disorders and develop combined prediction models.

METHODS

The clinicopathological characteristics, prenatal ultrasound images, and MRI features of 132 pregnant women with placenta accreta spectrum disorders at Xiangyang No. 1 People's Hospital were retrospectively reviewed from January 2016 to December 2020. In the training set of 99 patients, the ultrasound/MRI features model, clinical characteristics model, and combined model were developed by multivariate logistic regression analysis to predict the degree of placenta accreta spectrum disorders. The prediction performance of different models was compared using the Delong test. The developed models were validated by assessing their prediction performance in a test set of 33 patients.

RESULTS

The multivariate logistic regression analysis identified history of abortion, history of endometrial injury, and blurred boundary between the placenta and the myometrium/between the uterine serosa and the bladder to construct a combined model for predicting the degree of placenta accreta spectrum disorders (area under the curve (AUC) = 0.931; 95% confidence interval (CI): 0.882-0.980). The AUC of the clinical characteristics model and ultrasound/MRI features model was 0.858 (95% CI 0.794-0.921) and 0.709 (95% CI 0.624-0.798), respectively. The AUC of the combined model was significantly higher than that of the ultrasound/MRI features model (P < 0.001) or clinical characteristics model (P < 0.0015) in the training set. In the test set, the combined model also showed higher prediction performance.

CONCLUSIONS

Ultrasound/MRI-based signature is a powerful predictor for the degree of placenta accreta spectrum disorders in an early stage. A combined model (constructed with history of abortion, history of endometrial injury, and blurred boundary between the placenta and the myometrium/between the uterine serosa and the bladder) can improve the accuracy for predicting the degree of placenta accreta spectrum disorders in an early stage.

Suspected Placenta Accreta: Using Imaging to Stratify Risk of Morbidity

OBJECTIVE

This study was aimed to compare clinical outcomes and use of interventions in women with suspected accreta based on the degree of antenatal suspicion.

STUDY DESIGN

This was a retrospective cohort study of women with suspected accreta from 2007 to 2019. Included patients had one or more imaging studies suggestive of accreta. Cases were classified as "lower risk" if imaging showed possible signs of accreta including mild or superficial myometrial infiltration, an abnormal uterine contour, an abnormal uteroplacental interface, or loss of the retroplacental hypoechoic zone and "higher risk" if there was clear evidence of more than superficial myometrial infiltration, placental tissue extruding beyond the uterine serosa, bridging vessel(s), or placental lacunae with high velocity and/or turbulent flow. The primary study outcome was a composite maternal morbidity including cesarean hysterectomy, transfusion of blood or blood products, unintentional cystotomy, or intensive care unit (ICU) admission. Chi-square, Fisher's exact test, and Mann-Whitney U-test were used for analysis.

RESULTS

A total of 78 women had a suspected accreta on imaging, 36 with "lower risk" features and 42 with "higher risk" features. There were no differences in baseline maternal demographics. Women in the "higher risk" group were more likely to have a placenta previa (p < 0.01) and preoperative consultation with gynecologic oncology (p = 0.04). There was a significant difference in composite maternal morbidity between patients with "lower risk" and "higher risk" features of accreta on imaging (50 vs. 92.9%, p < 0.01). Median gestational age at planned and actual delivery were earlier in the "higher risk" group (36.6 vs. 34.9 weeks, p < 0.01; 36.0 vs. 34.7 weeks, p < 0.01).

CONCLUSION

Stratification of women with suspected accreta based on imaging corresponded to rates of maternal morbidity and operative complications, and appears to have been used clinically in selecting timing of delivery and interventions.

KEY POINTS

· Increased morbidity with high risk accreta imaging.. · Interventions correlate with accreta imaging risk.. · Imaging can be used to stratify accreta cases..

Predictive value of vascular endothelial growth factor and placenta growth factor for placenta accreta spectrum

This study aimed to assess the maternal features, Vascular Endothelial Growth Factor (VEGF) and Placenta Growth Factor (PLGF) in the Placenta Accreta Spectrum (PAS); then, to determine a predictive value of VEGF and PLGF in the PAS. This prospective case-control study was conducted on 90 pregnant women including 45 PAS, and 45 Normal Placenta (NP). Maternal age, gravidity, C/S, and serum levels of VEGF and PLGF were assessed between NP and PAS, and among NP and PAS sub-groups, including Placenta Accreta (PA), Placenta Increta (PI), and Placenta Percreta (PP). The Multi-gravidity, previous C/S, maternal age, and serum level of PLGF were significantly higher in the PAS group compared to the NP group OR = 42, 8.1, 1.17, and 1.002 (p-value <.05 for all); however, there was no difference regarding serum level of VEGF (p-value >.05). The same differences were seen among NP with PA, PI, and PP sub-groups (p-value <.05 for all, but p-value >.05 for VEGF). Placenta Previa was uniformly distributed across the PAS sub-groups (p-value >.05), also the VEGF and PLGF serum levels did not differ between PAS with Previa and PAS without Previa groups (p-value >.05). A valid cut-off point for PLGF was reported at 63.55. A predictive value of PLGF for the PAS patients is presented enjoying high accuracy and generalisability for the study population.Impact statementWhat is already known on this subject? The Placenta Accreta Spectrum (PAS), in which the placenta grows too deep in the uterine wall, is responsible for maternal-foetal morbidity and mortality worldwide; so, the antenatal diagnosis of PAS is an important key to improve maternal-foetal health. Normal placental implantation requires a fine balance among the levels of angiogenic and anti-angiogenic factors, such as the Placenta Growth Factor (PLGF), the Vascular Endothelial Growth Factor (VEGF), and soluble Fms-like tyrosine kinase-1. However, there is still controversy regarding The PLGF and VEGF level changes in PAS patients.What do the results of this study add? Despite traditional measuring the levels of PLGF and VEGF from the placenta at the time of delivery; in this study including 90 participants (28-34 weeks of gestation) the maternal serum levels of PLGF and VEGF were measured in advance (temporality causation), resulted in presenting a more valid cut-off point for PLGF in PAS group. In addition, the serum level of PLGF was significantly higher in the PAS and PAS sub-groups compared to the Normal Placenta group. Also, the Previa status of PAS patients did not affect the VEGF and PLGF serum levels.What are the implications of these findings for clinical practice and/or further research? PLGF cut-off point derived from the maternal serum level could predict PAS validly and, if used as a screening test in an earlier pregnancy, the maternal-foetal morbidity and mortality would decrease.

Cesarean Section for Placenta Previa and Placenta Previa Accreta Spectrum

According to the increase in the rate of cesarean section and the increase of high-aged pregnancy, we seem to more often encounter cases with placenta previa and placenta previa accrete spectrum. There are concerns about these cases, such as difficulty in controlling bleeding from the separation surface of placenta previa, the need for hysterectomy as a life-saving procedure, systemic management and hemostasis during massive hemorrhage, and treatment of disseminated intravascular coagulation (DIC). These cases are most frequently associated with cesarean hysterectomy.

Effectiveness of segmental resection technique in the treatment of placenta accreta spectrum

BACKGROUND

Placental accreta is a serious obstetrical entity and its management is challenging. The aim of this study was to evaluate and define our uterus sparing surgical technique in patients with placenta accreta spectrum.

METHODS

The data of 21 patients who underwent uterine segmental resection during cesarean section with a preliminary diagnosis of placenta accreta spectrum at Ege University between January 2017 and December 2018 were evaluated retrospectively.

RESULTS

Twenty-one patients were successfully treated with the segmental resection technique. In all cases, resected tissues were evaluated by histopathologically and the diagnosis of placenta accreta spectrum was confirmed. Hysterectomy was performed in two cases due to peri-partum hemorrhage that disrupted hemodynamics. None of the patients had complications such as visceral organ injury and wound infection.

CONCLUSION

Our technique of uterine sparing surgery seems to be safe and effective in the management of placenta accreta spectrum without increasing complication rates.