Magnetic resonance imaging is often misleading when used as an adjunct to ultrasound in the management of placenta accreta spectrum disorders

Radiomic study of antenatal prediction of severe placenta accreta spectrum from MRI

OBJECTIVES

We previously demonstrated the potential of radiomics for the prediction of severe histological placenta accreta spectrum (PAS) subtypes using T2-weighted MRI. We aim to validate our model using an additional dataset. Secondly, we explore whether the performance is improved using a new approach to develop a new multivariate radiomics model.

METHODS

Multi-centre retrospective analysis was conducted between 2018 and 2023. Inclusion criteria: MRI performed for suspicion of PAS from ultrasound, clinical findings of PAS at laparotomy and/or histopathological confirmation. Radiomic features were extracted from T2-weighted MRI. The previous multivariate model was validated. Secondly, a 5-radiomic feature random forest classifier was selected from a randomized feature selection scheme to predict invasive placenta increta PAS cases. Prediction performance was assessed based on several metrics including area under the curve (AUC) of the receiver operating characteristic curve (ROC), sensitivity, and specificity.

RESULTS

We present 100 women [mean age 34.6 (±3.9) with PAS], 64 of whom had placenta increta. Firstly, we validated the previous multivariate model and found that a support vector machine classifier had a sensitivity of 0.620 (95% CI: 0.068; 1.0), specificity of 0.619 (95% CI: 0.059; 1.0), an AUC of 0.671 (95% CI: 0.440; 0.922), and accuracy of 0.602 (95% CI: 0.353; 0.817) for predicting placenta increta. From the new multivariate model, the best 5-feature subset was selected via the random subset feature selection scheme comprised of 4 radiomic features and 1 clinical variable (number of previous caesareans). This clinical-radiomic model achieved an AUC of 0.713 (95% CI: 0.551; 0.854), accuracy of 0.695 (95% CI 0.563; 0.793), sensitivity of 0.843 (95% CI 0.682; 0.990), and specificity of 0.447 (95% CI 0.167; 0.667).

CONCLUSION

We validated our previous model and present a new multivariate radiomic model for the prediction of severe placenta increta from a well-defined, cohort of PAS cases.

ADVANCES IN KNOWLEDGE

Radiomic features demonstrate good predictive potential for identifying placenta increta. This suggests radiomics may be a useful adjunct to clinicians caring for women with this high-risk pregnancy condition.

Caesarean scar pregnancy presenting at 17 weeks with a journey involving an exploratory laparotomy, continuing pregnancy and delivery at 34 weeks: A case report

Caesarean scar pregnancy (CSP) occurs when the gestational sac implants in the region of a scar from a previous caesarean delivery. CSP can lead to life-threatening complications, including severe haemorrhage, uterine rupture, placenta accreta spectrum (PAS) and hysterectomy. A 40-year-old woman with one previous caesarean was referred to the specialist centre at 17+1 weeks of gestation with concerns about CSP. At 19 weeks, she was admitted with abdominal pain. Due to raised body habitus, accurate ultrasound assessment was challenging, necessitating reliance on magnetic resonance imaging (MRI). The patient desired to continue the pregnancy, but due to pain and concerns about uterine rupture she consented to a laparotomy to potentially terminate the pregnancy. Findings during the laparotomy were reassuring, leading to the decision not to terminate the pregnancy. The patient remained hospitalised until delivery by caesarean-hysterectomy at 33+6 weeks. Histopathology confirmed the PAS diagnosis. This case highlights the importance of achieving early diagnosis and obtaining clear sonographic findings. It emphasises the pitfalls of relying on MRI due to its tendency to over-diagnose severity. It emphasises the urgency for improved training in this domain. Early sonographic diagnosis allows safer performance of termination of pregnancy. It also provides women who continue with the pregnancy useful prognostic signs to facilitate decisions on the optimal gestation for delivery. Determining optimal conservative management for CSP remains an ongoing challenge. This case emphasises the importance of multidisciplinary discussion, comprehensive patient counselling and involving patients in their care planning, to create an individualised and adaptable treatment plan.

First-trimester screening for placenta accreta spectrum

In recent years, there has been a significant rise in cases of placenta accreta spectrum, a group of life-threatening placental disorders that can arise during childbirth. Early detection plays a crucial role in facilitating meticulous delivery planning, ultimately leading to a reduction in mortality and morbidity rates and improved overall outcomes. Although third-trimester ultrasound has traditionally been the primary method for prenatal screening for placenta accreta spectrum, it often falls short in identifying cases or diagnosis is too late for optimal delivery planning. Emerging evidence has highlighted the option of early detection of placenta accreta spectrum indicators during the first trimester of pregnancy. This comprehensive review delves into our current knowledge of sonographic assessment of the uterine cervicoisthmic complex in the first trimester, examining the location and appearance of cesarean scars and exploring first-trimester screening strategies, ultimately paving the way for improved maternal and neonatal outcomes.

Pregnancy-specific beta-1-glycoprotein 6 is a potential novel diagnostic biomarker of placenta accreta spectrum

Early diagnosis is essential for the safer perinatal management of placenta accreta spectrum (PAS). We used transcriptome analysis to investigate diagnostic maternal serum biomarkers and the mechanisms of PAS development. We analyzed eight formalin-fixed paraffin-embedded placental specimens from two placenta increta and three placenta percreta cases who underwent cesarean hysterectomy at Sapporo Medical University Hospital between 2013 and 2019. Invaded placental regions were isolated from the uterine myometrium and RNA was extracted. The transcriptome difference between normal placenta and PAS was analyzed by microarray analysis. The PAS group showed markedly decreased expression of placenta-specific genes such as LGALS13 and the pregnancy-specific beta-1-glycoprotein (PSG) family. Term enrichment analysis revealed changes in genes related to cellular protein catabolic process, female pregnancy, autophagy, and metabolism of lipids. From the highly dysregulated genes in the PAS group, we investigated the expression of PSG family members, which are secreted into the intervillous space and can be detected in maternal serum from the early stage of pregnancy. The gene expression level of PSG6 in particular was progressively decreased from placenta increta to percreta. The PSG family, especially PSG6, is a potential biomarker for PAS diagnosis.

Magnetic resonance imaging improves diagnosis of placenta accreta spectrum requiring hysterectomy compared to ultrasound

BACKGROUND

Magnetic resonance imaging has been used increasingly as an adjunct for ultrasound imaging for placenta accreta spectrum assessment and preoperative surgical planning, but its value has not been established yet. The ultrasound-based placenta accreta index is a well-validated standardized approach for placenta accreta spectrum evaluation. Placenta accreta spectrum-magnetic resonance imaging markers have been outlined in a joint guideline from the Society of Abdominal Radiology and the European Society of Urogenital Radiology.

OBJECTIVE

This study aimed to compare placenta accreta spectrum-magnetic resonance imaging parameters with the ultrasound-based placenta accreta index in pregnancies at high risk for placenta accreta spectrum and to assess the additional diagnostic value of magnetic resonance imaging for placenta accreta spectrum that requires a cesarean hysterectomy.

STUDY DESIGN

This was a single-center, retrospective study of pregnant patients who underwent magnetic resonance imaging, in addition to ultrasonography, because of suspected placenta accreta spectrum. The ultrasound-based placenta accreta index and placenta accreta spectrum-magnetic resonance imaging parameters were obtained. Student's t test and Fisher's exact test were used to compare the groups in terms of the primary outcome (hysterectomy vs no hysterectomy). The diagnostic performance of magnetic resonance imaging and the ultrasound-based placenta accreta index was assessed using multivariable logistic regressions, receiver operating characteristics curves, the DeLong test, McNemar test, and the relative predictive value test.

RESULTS

A total of 82 patients were included in the study, 41 of whom required a hysterectomy. All patients who underwent a hysterectomy met the International Federation of Gynecology and Obstetrics clinical evidence of placenta accreta spectrum at the time of delivery. Multiple parameters of the ultrasound-based placenta accreta index and placenta accreta spectrum-magnetic resonance imaging were able to predict hysterectomy, and the parameter of greatest dimension of invasion by magnetic resonance imaging was the best quantitative predictor. At 96% sensitivity for hysterectomy, the cutoff values were 3.5 for the ultrasound-based placenta accreta index and 2.5 cm for the greatest dimension of invasion by magnetic resonance imaging. Using this sensitivity, the parameter of greatest dimension of invasion measured by magnetic resonance imaging had higher specificity (P=.0016) and a higher positive predictive value (P=.0018) than the ultrasound-based placenta accreta index, indicating an improved diagnostic threshold.

CONCLUSION

In a suspected high-risk group for placenta accreta spectrum, magnetic resonance imaging identified more patients who will not need a hysterectomy than when using the ultrasound-based placenta accrete index only. Magnetic resonance imaging has the potential to aid patient counseling, surgical planning, and delivery timing, including preterm delivery decisions for patients with placenta accreta spectrum requiring hysterectomy.

A Deep Learning Pipeline Using Prior Knowledge for Automatic Evaluation of Placenta Accreta Spectrum Disorders With MRI

BACKGROUND

The diagnosis of prenatal placenta accreta spectrum (PAS) with magnetic resonance imaging (MRI) is highly dependent on radiologists' experience. A deep learning (DL) method using the prior knowledge that PAS-related signs are generally found along the utero-placental borderline (UPB) may help radiologists, especially those with less experience, to mitigate this issue.

PURPOSE

To develop a DL tool for antenatal diagnosis of PAS using T2-weighted MR images.

STUDY TYPE

Retrospective.

SUBJECTS

Five hundred and forty pregnant women with clinically suspected PAS disorders from two institutions, divided into training (409), internal test (103), and external test (28) datasets.

FIELD STRENGTH/SEQUENCE

Sagittal T2-weighted fast spin echo sequence at 1.5 T and 3 T.

ASSESSMENT

An nnU-Net was trained for placenta segmentation. The UPB straightening approach was used to extract the utero-placental boundary region. The UPB image was then fed into DenseNet-PAS for PAS diagnosis. DenseNet-PP learnt placental position information to improve the PAS diagnosis performance. Three radiologists with 8, 10, and 12 years of experience independently evaluated the images. Two radiologists marked the placenta tissue. Histopathological findings were the reference standard.

STATISTICAL TESTS

Area under the curve (AUC) was used to evaluate the classification. Dice coefficient evaluated the segmentation between radiologists and the model performance. The Mann-Whitney U-test or the chi-squared test assessed the significance of differences. Decision curve analysis was used to determine clinical effectiveness. DeLong's test was used to compare AUCs.

RESULTS

Of the 540 patients, 170 had PAS disorders confirmed by histopathology. The DL model using UPB images and placental position yielded the highest AUC of 0.860 and 0.897 in internal test and external test cohorts, respectively, significantly exceeding the performance of three radiologists (internal test AUC, 0.737-0.770).

DATA CONCLUSION

By extracting the UPB image, this fully automatic DL pipeline achieved high accuracy and may assist radiologists in PAS diagnosis using MRI.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

Extensive fundal placenta accreta spectrum (PAS) in a nulliparous patient with an unscarred uterus and systemic lupus erythematosus (SLE) necessitating cesarean hysterectomy at delivery

Placenta accreta spectrum (PAS) defined by various degrees of abnormally invasive placentation is strongly associated with severe maternal morbidity and maternal mortality, mainly reflecting maternal hemorrhage. Predisposing factors for this condition include: multiparity, placenta previa, previous uterine surgeries (previous curettage, cesarean delivery, and myomectomy), smoking and previous PAS. Prenatal sonographic findings associated with PAS include the presence of placenta previa, loss of the hypoechoic retroplacental sonolucency, myometrial thinning, interruption of the irregularity of the bladder wall, excessive vascularity of the uterovesical plane, placental lacunae, increased placental vascularity, bridging vessels with vascularity extending from the placental bed across the uterine wall into the bladder or other pelvic organs. PAS is very rare among nulliparous patients, especially those without previous uterine surgery. We describe an unusual case of PAS in a nulliparous patient with an unscarred uterus and systemic lupus erythematosus in whom a fundal placenta with PAS and thinned and areas of absent myometrium suspected at midtrimester sonography, sustained uterine atony and severe hemorrhage at delivery, necessitated massive blood transfusion and subtotal hysterectomy. Both mother and infant did well. Pathology confirmed PAS and marked uterine thinning. Although PAS most commonly is associated with placenta previa and the presence of previous cesarean delivery, this case emphasizes the need for alertness of at times subtle prenatal sonographic findings of PAS irrespective of placental location even among nulliparous patients, especially those with systemic lupus erythematosus.

Placental Area in the Lower Uterine Segment, Cervical Length, and Clinical Outcome in Pregnancies With Complete Placenta Previa

BACKGROUND

Complete placenta previa is associated with a higher percentage of adverse clinical outcomes and magnetic resonance imaging (MRI) is widely used in the preoperative examination of patients with placenta previa.

PURPOSE

To evaluate the effectiveness of the placental area in the lower uterine segment and cervical length in identifying the adverse maternal-fetal outcomes in women with complete placenta previa.

STUDY TYPE

Retrospective.

POPULATION

A total of 141 pregnant women (median age, 32; age range, 24-40 years) with complete placenta previa were examined by MRI to evaluate the uteroplacental condition.

FIELD STRENGTH/SEQUENCE

A 3 T with T1 -weighted imaging (T1 WI), T2 -weighted imaging (T2 WI), and half-Fourier acquisition single-shot turbo spin echo (HASTE) sequence.

ASSESSMENT

The association of the placental area in the lower uterine segment and cervical length measured using MRI with the risk of massive intraoperative hemorrhage (MIH) and maternal-fetal perinatal outcomes were determined. The adverse neonatal outcomes (preterm delivery, respiratory distress syndrome [RDS], admission to neonatal intensive care unit [NICU]) were analyzed in different groups.

STATISTICAL TESTS

The t-test, Mann-Whitney U test, Chi-square, Fisher's exact test, and receiver operating characteristic (ROC) curve were used, and a P < 0.05 indicated a statistically significant difference.

RESULTS

The mean operation time, intraoperative blood loss, and intraoperative blood transfusing were significantly higher in patients with large placental area and short cervix than in patients with the small placental area and long cervix, respectively. The incidence of adverse neonatal outcomes was significantly higher in the large placenta area group and short cervix group than in the small placenta group area and long cervix group, respectively, such as preterm delivery, RDS, and NICU. By combining placental area with cervical length sensitivity and specificity increased to 93% and 92%, respectively, for the identification of MIH > 2000 mL with area under the receiver operating curve (AUC) 0.941.

DATA CONCLUSION

Large placental area and short cervical length may be associated with a high risk of MIH and adverse maternal-fetal perinatal outcomes in patients with complete placenta previa.

LEVEL OF EVIDENCE: 3

TECHNICAL EFFICACY STAGE

2.

Factors Limiting Magnetic Resonance Imaging Diagnosis of Placenta Accreta Spectrum

OBJECTIVE

Placenta accreta spectrum (PAS) disorders are characterized by an abnormal adherence of the placenta to the uterine myometrium. Magnetic resonance imaging (MRI) is an important adjunct in antenatal diagnosis. We sought to determine if there are patient and MRI characteristics that limit the accuracy of PAS diagnosis and degree of invasion.

STUDY DESIGN

We conducted a retrospective cohort analysis of patients who were evaluated for PAS by MRI from January 2007 to December 2020. Patient characteristics evaluated included number of prior cesarean deliveries, history of dilation and curettage (D&C) or dilation and evacuation (D&E), short interval pregnancy less than 18 months, and delivery body mass index (BMI). All patients were followed until delivery and MRI diagnosis was compared with final histopathology.

RESULTS

Of the 353 patients with suspected PAS, 152 (43%) underwent MRI evaluation and were included in the final analysis. In patients who underwent MRI evaluation, 105 (69%) had confirmed PAS on pathology. Patient characteristics were similar between groups and not associated with accuracy of MRI diagnosis. MRI was accurate in diagnosing PAS and the associated degree of invasion in 83 (55%) patients. Accuracy was associated with lacunae (8 vs. 0%, p = 0.02), abnormal bladder interface (25 vs. 6%, p = 0.002), and T1 hyperintensity (13 vs. 1%, p = 0.002). Of the 69 (45%) patients in whom MRI was inaccurate, overdiagnosis was seen in 44 (64%) patients and underdiagnosis in 25 (36%) patients. Overdiagnosis was significantly associated with dark T2 bands (45 vs. 22%, p = 0.005). Underdiagnosis was associated with earlier gestational age at MRI (28 vs. 30 weeks, p = 0.049) and lateral placentation (16 vs. 2.4%, p = 0.025).

CONCLUSION

Patient factors did not change MRI accuracy of PAS diagnosis. MRI is associated with a significant overdiagnosis of PAS when dark T2 bands are present, and underdiagnose PAS when performed earlier in gestation or when lateral placentation is present.

KEY POINTS

· Patient factors are not associated with MRI accuracy of PAS diagnosis.. · MRI overdiagnoses PAS invasion when there are dark T2 bands.. · MRI underdiagnoses PAS invasion when performed earlier in gestation.. · Underdiagnosis of PAS is associated with lateral placentation..

Radiomics-based prediction of FIGO grade for placenta accreta spectrum

BACKGROUND

Placenta accreta spectrum (PAS) is a rare, life-threatening complication of pregnancy. Predicting PAS severity is critical to individualise care planning for the birth. We aim to explore whether radiomic analysis of T2-weighted magnetic resonance imaging (MRI) can predict severe cases by distinguishing between histopathological subtypes antenatally.

METHODS

This was a bi-centre retrospective analysis of a prospective cohort study conducted between 2018 and 2022. Women who underwent MRI during pregnancy and had histological confirmation of PAS were included. Radiomic features were extracted from T2-weighted images. Univariate regression and multivariate analyses were performed to build predictive models to differentiate between non-invasive (International Federation of Gynecology and Obstetrics [FIGO] grade 1 or 2) and invasive (FIGO grade 3) PAS using R software. Prediction performance was assessed based on several metrics including sensitivity, specificity, accuracy and area under the curve (AUC) at receiver operating characteristic analysis.

RESULTS

Forty-one women met the inclusion criteria. At univariate analysis, 0.64 sensitivity (95% confidence interval [CI] 0.0-1.00), specificity 0.93 (0.38-1.0), 0.58 accuracy (0.37-0.78) and 0.77 AUC (0.56-.097) was achieved for predicting severe FIGO grade 3 PAS. Using a multivariate approach, a support vector machine model yielded 0.30 sensitivity (95% CI 0.18-1.0]), 0.74 specificity (0.38-1.00), 0.58 accuracy (0.40-0.82), and 0.53 AUC (0.40-0.85).

CONCLUSION

Our results demonstrate a predictive potential of this machine learning pipeline for classifying severe PAS cases.

RELEVANCE STATEMENT

This study demonstrates the potential use of radiomics from MR images to identify severe cases of placenta accreta spectrum antenatally.

KEY POINTS

• Identifying severe cases of placenta accreta spectrum from imaging is challenging. • We present a methodological approach for radiomics-based prediction of placenta accreta. • We report certain radiomic features are able to predict severe PAS subtypes. • Identifying severe PAS subtypes ensures safe and individualised care planning for birth.

External Validation of a Multivariable Prediction Model for Placenta Accreta Spectrum

BACKGROUND

Placenta accreta spectrum (PAS) is a disorder of abnormal placentation associated with severe postpartum hemorrhage, maternal morbidity, and mortality. Predelivery prediction of this condition is important to determine appropriate delivery location and multidisciplinary planning for operative management. This study aimed to validate a prediction model for PAS developed by Weiniger et al in 2 cohorts who delivered at 2 different United States tertiary centers.

METHODS

Cohort A (Brigham and Women's Hospital; N = 253) included patients with risk factors (prior cesarean delivery and placenta previa) and/or ultrasound features of PAS presenting to a tertiary-care hospital. Cohort B (Columbia University Irving Medical Center; N = 99) consisted of patients referred to a tertiary-care hospital specifically because of ultrasound features of PAS. Using the outcome variable of surgical and/or pathological diagnosis of PAS, discrimination (via c-statistic), calibration (via intercept, slope, and flexible calibration curve), and clinical usefulness (via decision curve analysis) were determined.

RESULTS

The model c-statistics in cohorts A and B were 0.728 (95% confidence interval [CI], 0.662-0.794) and 0.866 (95% CI, 0.754-0.977) signifying acceptable and excellent discrimination, respectively. The calibration intercept (0.537 [95% CI, 0.154-0.980] for cohort A and 3.001 [95% CI, 1.899- 4.335] for B), slopes (0.342 [95% CI, 0.170-0.532] for cohort A and 0.604 [95% CI, -0.166 to 1.221] for B), and flexible calibration curves in each cohort indicated that the model underestimated true PAS risks on average and that there was evidence of overfitting in both validation cohorts. The use of the model compared to a treat-all strategy by decision curve analysis showed a greater net benefit of the model at a threshold probability of >0.25 in cohort A. However, no net benefit of the model over the treat-all strategy was seen in cohort B at any threshold probability.

CONCLUSIONS

The performance of the Weiniger model is variable based on the case-mix of the population with regard to PAS clinical risk factors and ultrasound features, highlighting the importance of spectrum bias when applying this PAS prediction model to distinct populations. The model showed benefit for predicting PAS in populations with substantial case-mix heterogeneity at threshold probability of >25%.

Uterus-preserving surgical management of placenta accreta spectrum disorder: a large retrospective study

BACKGROUND

The two-child policy implemented in China resulted in a surge of high-risk pregnancies among advanced maternal aged women and presented a window of opportunity to identify a large number of placenta accreta spectrum (PAS) cases, which often invoke severe blood loss and hysterectomy. We thus had an opportunity to evaluate the surgical outcomes of a unique conservative PAS management strategy for uterus preservation, and the impacts of magnetic resonance imaging (MRI) in PAS surgical planning.

METHODS

Cross-sectional study, comparing the outcomes of a new uterine artery ligation combined with clover suturing technique (UAL + CST) with the existing conservative surgical approaches in a maternal public hospital with an annual birth of more than 20,000 neonates among all placenta previa cases suspecting of PAS between January 1, 2015 and December 31, 2018.

RESULTS

From a total of 89,397 live births, we identified 210 PAS cases from 400 singleton pregnancies with placenta previa. Aside from 2 self-requested natural births (low-lying placenta), all PAS cases had safe cesarean deliveries without any total hysterectomy. Compared with the existing approaches, the evaluated UAL + CST had a significant reduction in intraoperative blood loss (β=-312 ml, P < .001), RBC transfusion (β=-1.08 unit, P = .001), but required more surgery time (β = 16.43 min, P = .01). MRI-measured placenta thickness, when above 50 mm, can increase blood loss (β = 315 ml, P = .01), RBC transfusion (β = 1.28 unit, P = .01), surgery time (β = 48.84 min, P < .001) and hospital stay (β = 2.58 day, P < .001). A majority of percreta patients resumed normal menstrual cycle within 12 months with normal menstrual fluid volume, without abnormal urination or defecation.

CONCLUSIONS

A conservative surgical management approach of UAL + CST for PAS is safe and effective with a low complication rate. MRI might be useful for planning PAS surgery.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR2000035202.

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.

Imaging the Uterus in Placenta Accreta Spectrum Disorder

Antenatal diagnosis of placenta accreta spectrum (PAS) improves maternal and neonatal outcomes by allowing for multidisciplinary planning and preparedness. Ultrasound is the primary imaging tool. Simplification and standardization of placental evaluation and reporting terminology allows improved communication and understanding between teams. Prior to 10 weeks of gestation, gestational sac position and least myometrial thickness surrounding the gestational sac help PAS diagnosis very early in pregnancy. Late first-, second-, and third-trimester evaluation includes comprehensive evaluation of the placenta, transabdominal and transvaginal with partially full maternal urinary bladder, and by color Doppler. Subsequently, the sonologist should indicate whether the evaluation was optimal or suboptimal; the level of suspicion as low, moderate, or high; and the extent as focal, global, or extending beyond the uterus. Other complementary imaging modalities such as 3D-power Doppler ultrasound, magnetic resonance imaging (MRI), and vascular topography mapping strive to improve antenatal placental evaluation but remain investigational at present. KEY POINTS: · Antenatal imaging, primarily using ultrasound with partially full maternal urinary bladder, is an essential means of evaluation of those at risk for PAS.. · Simplification and standardization of placental evaluation and reporting will allow improved communication between the multidisciplinary teams.. · Gestational sac location prior to 10 weeks of gestation and four markers after that (placental lacunae and echostructure, myometrial thinning, hypoechoic zone with or without bulging between placenta and myometrium, and increased flow on color Doppler)..

Placenta Accreta Spectrum and Postpartum Hemorrhage

Placenta accreta spectrum is a group of disorders involving abnormal trophoblastic invasion to the deep layers of endometrium and myometrium. Placenta accrete spectrum is one of the major causes of severe maternal morbidity, with increasing incidence in the past decade mainly secondary to an increase in cesarean deliveries. Severity varies depending on the depth of invasion, with the most severe form, known as percreta, invading uterine serosa or surrounding pelvic organs. Diagnosis is usually achieved by ultrasound, and MRI is sometimes used to assess invasion. Management usually involves a hysterectomy at the time of delivery. Other strategies include delayed hysterectomy or expectant management.

The prenatal diagnostic indicators of placenta accreta spectrum disorders

Placenta accreta spectrum (PAS) disorders refers to a heterogeneous group of anomalies distinguished by abnormal adhesion or invasion of chorionic villi through the myometrium and uterine serosa. PAS frequently results in life-threatening complications, including postpartum hemorrhage and hysterotomy. The incidence of PAS has increased recently as a result of rising cesarean section rates. Consequently, prenatal screening for PAS is essential. Despite the need to increase specificity, ultrasound is still considered a primary adjunct. Given the dangers and adverse effects of PAS, it is necessary to identify pertinent markers and validate indicators to improve prenatal diagnosis. This article summarizes the predictors regarding biomarkers, ultrasound indicators, and magnetic resonance imaging (MRI) features. In addition, we discuss the effectiveness of joint diagnosis and the most recent research on PAS. In particular, we focus on (a) posterior placental implantation and (b) accreta after in vitro fertilization-embryo transfer, both of which have low diagnostic rates. At last, we graphically display the prenatal diagnostic indicators and each diagnostic performance.

Ferumoxytol-enhanced MR demonstration of changes to internal placental structure in placenta accreta spectrum: Preliminary findings

INTRODUCTION

The goal of this pilot study is to determine if ferumoxytol-enhanced MR might provide a new approach to the diagnosis of placenta accreta spectrum (PAS), and if so, to identify signs of PAS.

METHODS

Ten pregnant women were referred for MRI evaluation for PAS. MR studies consisted of pre-contrast SSFSE, SSFP, DWI, and ferumoxytol-enhanced sequences. Post-contrast images were rendered as MIP and MinIP images to separately display the maternal and fetal circulations respectively. Two readers examined the images for architectural changes to placentone (fetal cotyledon) that might distinguish PAS cases from normal. Attention was given to the size and morphology of the placentone, villous tree, and vascularity. In addition, the images were examined for evidence of fibrin/fibrinoid, intervillous thrombus, basal and chorionic plate bulges. Interobserver agreement was characterized with kappa coefficients and levels of confidence for feature identification was recorded on a 10-point scale.

RESULTS

At delivery, there were five normal placentas and five with PAS (one accreta, two increta, two percreta). The ten changes of placental architecture in PAS included: focal/regional expansion of placentone(s); lateral displacement and compression of the villous tree; disruption of a regular pattern of normal placentones; bulging of the basal plate; bulging of the chorionic plate; transplacental stem villi; linear/nodular bands at basal plate; non-tapering villous branches; intervillous hemorrhage; and dilated subplacental vessels. All these changes were more common in PAS; the first five achieved statistical significance in this small sample. The interobserver agreement and confidence for the identification of these features was good to excellent except for dilated subplacental vessels.

DISCUSSION

Ferumoxytol-enhanced MR imaging appears to depict derangements of the internal architecture of placentas with PAS, thereby suggesting a promising new strategy to diagnose PAS.

Systematic review and meta-analysis on placenta accreta spectrum disorders in twin pregnancies: risk factors, detection rate and histopathology

INTRODUCTION

The occurrence of PAS has been recently associated with the presence of twin pregnancy. Aim of this review is to report the risk factors, histopathological correlation, diagnostic accuracy of prenatal ultrasound and clinical outcome of twin pregnancies complicated by placenta accreta spectrum (PAS) disorders.

EVIDENCE ACQUISITION

PubMed, Embase, Cinahl, Clinical Trial.Gov and Google Scholar databases were searched. Inclusion criteria were studies on twin pregnancies complicated by PAS. The outcomes explored were risk factors for PAS (including placenta previa, prior uterine surgery or assisted reproductive technology, ART), histopathology (placenta accreta and increta/percreta), detection rate of prenatal ultrasound and clinical outcome, including need for blood transfusion, hysterectomy, emergency or scheduled Cesarean delivery (CD), and maternal death. Random effect meta-analyses of proportions were sued to combine the data.

EVIDENCE SYNTHESIS

Two studies considering 103 pregnancies were included in this systematic review: 41.86% (95% CI 27.0-57.9) of twin pregnancies complicated by PAS disorders had a prior CD, 28.22% (95% CI 13.4-46.0) presented placenta previa and 58.14% (95% CI 42.1-73.0) of twin pregnancies were conceived by ART. 74.49% (95% CI 41.6-96.5) of PAS in twin pregnancies were placenta accreta, while 25.51% (95% CI 3.5-58.4) were placenta increta or percreta. Prenatal diagnosis of PAS in twin pregnancies was accomplished only in 27.91% (95% CI 15.3-43.7) of cases. Finally, only one study consistently reported the clinical outcome of PAS in twins. 31.67% (95% CI 20.3-45.0) of women required blood transfusion, 26.67% (95% CI 16.1-39.7) had hysterectomy, while there was no case of maternal death. 44.19% of women had an emergency CD.

CONCLUSIONS

There is still limited evidence on the clinical course of PAS disorders in twin pregnancies. Placenta previa, prior uterine surgery (mainly CD), and ART are the most commonly risk factors for PAS disorders in twins. Prenatal diagnosis of PAS in twins is lower compared to what reported in singleton. Finally, about 30% of women with a twin pregnancy complicated by PAS required blood transfusion and hysterectomy.

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.

The effect of abnormal placentation on maternal serum fetal fraction of cell-free DNA

OBJECTIVES

Abnormal placentation may affect the maternal serum fraction of cell-free fetal DNA (fetal fraction) determined as part of non-invasive prenatal screening (NIPS). This study aimed to assess whether the fetal fraction can predict placenta accreta spectrum (PAS) with or without placenta previa (PP). We also investigated the impact of trophoblastic invasion depth on the fetal fraction.

METHODS

This is a retrospective case-control study of pregnant women with and without abnormal placentation carrying a singleton and having undergone NIPS prior to 20 weeks of gestation. The eligible subjects were selected from a cohort managed at our institution for PAS suspected antenatally. We compared women with normal placentation (controls) to PAS, PP, or PAS + PP cases. Data were abstracted from electronic medical records, and PAS was confirmed histologically.

RESULTS

Of the 146 patients in our cohort, 8 controls, 10 PP, 6 PAS, and 7 PAS + PP cases were eligible for the study. Among the groups, there were no significant differences in baseline demographic and clinical characteristics except the median number of prior uterine surgeries. Also, the groups did not significantly differ in their median fetal fraction. The fetal fraction did not discriminate any group when stratified according to the depth of placental invasion, i.e., no PAS, abnormally adherent, and abnormally invasive placenta.

CONCLUSIONS

The maternal serum fraction of cell-free fetal DNA measured before 20 weeks of gestation is not predictive of PAS with or without concurrent PP or the depth of trophoblastic invasion.

Accuracy of ultrasound for the detection of placenta accreta spectrum in a universal screening population

OBJECTIVES

The current study aimed to determine the sensitivity and specificity of ultrasound for the diagnosis of placenta accreta spectrum (PAS) in a universal screening population and assesses the added value of magnetic resonance imaging (MRI).

METHODS

This retrospective analysis evaluated 5219 patients with singleton pregnancies who had a standardized ultrasound (US) examination in our unit and delivered at our institution between 2014 and 2019.

RESULTS

A total of 181 (3.5%) of 5219 (100%) patients had a suspicion or diagnosis of PAS with US. The accuracy of US in detecting placenta increta/percreta showed a sensitivity of 100%, specificity of 99.9%, positive predictive value of 82.4%, and a negative predictive value of 100%. The diagnosis of all forms of PAS showed a sensitivity of 25.8%, specificity of 99.8%, positive predictive value of 80.8%, and a negative predictive value of 97.7%. MRI was concordant with US in 11 of 14 (78.5%) cases of severe forms of PAS and in three of 15 (20.0%) cases with placenta accreta.

CONCLUSION

A standardized US evaluation can be applied in a universal screening setting for the diagnosis of severe forms of PAS. MRI is a complementary examination in severe forms of PAS but seems of limited value to discriminate placenta accreta from placenta increta/percreta.

Placenta Accreta Spectrum: Prenatal Diagnosis and Management

The incidence of placenta accreta spectrum (PAS) is increasing and is now about 3 per 1000 deliveries, largely due to the rising cesarean section rate. Ultrasound is the preferred method for diagnosis of PAS. Ultrasound markers include multiple vascular lacunae, loss of the hypoechoic retroplacental zone, abnormalities of the uterine serosa-bladder interface, retroplacental myometrial thickness less than 1 mm, increased placental vascularity, and observation of bridging vessels linking the placenta and bladder. Patients with PAS should be managed by experienced multidisciplinary teams. Hysterectomy is the accepted management of PAS and conservative or expectant management of PAS should be considered investigational.

Percreta score to differentiate between placenta accreta and placenta percreta with ultrasound and MR imaging

INTRODUCTION

The objective of this study was to assess the performance of ultrasound and magnetic resonance imaging (MRI) features in helping to classify the type of placenta accreta spectrum (PAS; accreta/increta vs percreta), alone or combined in a predictive score.

MATERIAL AND METHODS

We conducted a retrospective study in 82 pregnant women with PAS who underwent ultrasound and MRI examination of the pelvis before delivery (from an initial cohort of 185 women with PAS). We estimated the sensitivity, specificity and accuracy of MRI and ultrasound in the diagnosis of the type of PAS. We analyzed cesarean and imaging features using univariable logistic regression analysis. We constructed a nomogram to predict the risk of placenta percreta and validated it with bootstrap resampling, then used receiver operating characteristic curves to assess the performance of the model in distinguishing between placenta percreta and placenta accreta/increta.

RESULTS

Among the 82 patients, 29 (35%) had placenta accreta/increta and 53 (65%) had placenta percreta. The best features to discriminate between placenta accreta/increta and placenta percreta with ultrasound were increased vascularization at the uterine serosa-bladder wall interface (odds ratio [OR] 7.93; 95% confidence interval [CI] 2.78-24.99; p < 0.01) and the number of lacunae without a hyperechogenic halo (OR 1.36; 95% CI 1.14-1.67; p = 0.012). Concerning MRI markers, heterogeneous placenta (OR 12.89; 95% CI 3.05-89.16; p = 0.002), dark intraplacental bands (OR 12.89; 95% CI 3.05-89.16; p = 0.002) and bladder wall interruption (OR 15.89; 95% CI 4.78-73.33; p < 0.001) had a higher OR in discriminating placenta accreta/increta from placenta percreta. The nomogram yielded areas under the curve of 0.841 (95% CI 0.754-0.927) and 0.856 (95% CI 0.767-0.945), after bootstrap resampling, for the accurate prediction of placenta percreta.

CONCLUSIONS

The nomogram we developed to predict the risk of placenta percreta among patients with PAS had good discriminative capabilities. This performance and its impact on maternal morbidity should be confirmed by future prospective studies.

Outcomes of pregnancies at high-risk for placenta accreta spectrum following negative diagnostic imaging

OBJECTIVES

To assess the pretest and negative post-test probability for placenta accreta spectrum (PAS) in a group of patients with high-risk clinical factors.

METHODS

We included patients with suspected and/or confirmed PAS at our institution over 8 years. Sonography performed by maternal-fetal medicine specialists, and selected patients underwent MRI. Imaging was considered positive if either sonography or MRI suggested PAS. Histopathology was the gold standard for diagnosis of PAS. We assessed the pretest and negative imaging-test probability, and resources required.

RESULTS

We identified 82 high-risk patients with the following: (1) a history of ≥1 cesarean section and/or intrauterine gynecologic procedure and placenta previa in the index pregnancy; (2) a history of >3 cesarean deliveries and/or gynecologic procedures regardless of placental location; (3) prior PAS disorder, or retained placenta requiring manual extraction and/or curettage, complicated by postpartum hemorrhage; and (4) suspected cesarean section scar pregnancy. Histopathology confirmed PAS in 52 patients, with pretest probability of 63%. Imaging correctly identified 44/50 cases with PAS, and excluded this condition in 24/30 cases. Thus, the positive and negative post-test probability for PAS following negative imaging was 88 and 20%, respectively. Of the six patients with false-negative imaging, all had either surgical complications or required care beyond that for routine cesarean section.

CONCLUSIONS

Although diagnostic imaging is sensitive, the negative posttest probability remains high in women with high pretest probability for PAS. Therefore, women at high risk for PAS should be managed in experienced centers by a multidisciplinary team even if imaging is negative.

Association between placenta accreta spectrum and third-trimester serum levels of vascular endothelial growth factor, placental growth factor, and soluble Fms-like tyrosine kinase-1: A meta-analysis

AIM

Antenatal suspicion of placenta accreta spectrum (PAS) currently relies on ultrasonographic findings, color doppler, and MRI, which have rendered it operator and expertise-dependent. No serum markers for PAS have been integrated into clinical practice yet. The aim of this meta-analysis was to identify potential serum markers for PAS by investigating third-trimester serum levels of vascular endothelial growth factor (VEFG), placental growth factor (PIGF), and soluble Fms-like tyrosine kinase-1 (sFlt-1) among PAS-cases and controls.

METHODS

PubMed, Scopus, EBSCO, Web of Science, and CNKI databases were systematically searched for relevant articles. Random-effects model was applied to calculate the overall standardized mean difference (SMD) for each marker. Subgroup analysis and meta-regression were performed to assess for potential covariates.

RESULTS

Eight studies involving 366 PAS-cases and 518 controls were included. Third trimester sFlt-1 levels were significantly lower in PAS-cases when compared to controls (SMD = -7.76, 95%CI = -10.42 to -5.10). This was, to a certain extent, consistent among studies though they differed in their extent of significance. Levels of VEGF (SMD = 1.59, 95%CI = -0.07 to 3.25) and PlGF (SMD = -0.49, 95%CI = -1.66 to 0.67) were not significantly different between PAS cases and controls, in which studies demonstrated conflicting results.

CONCLUSIONS

Third trimester sFlt-1 levels may be useful to predict PAS. Nonetheless, further studies are recommended to better understand conflicting results before adopting either VEGF or PlGF.

Ultrasound and magnetic resonance imaging in the diagnosis of clinically significant placenta accreta spectrum disorders

OBJECTIVES

We aimed to assess the performance of ultrasound (US) and magnetic resonance imaging (MRI) signs for antenatal detection of placenta accreta spectrum (PAS) disorders in women with placenta previa (placental edge ≤2 cm from the internal uterine orifice, ≥26^0/7 weeks' gestation) with and without a history of previous Caesarean section.

METHODS

Single center prospective observational study. US suspicion of PAS was raised in the presence of obliteration of the hypoechoic space between uterus and placenta, interruption of the hyperechoic uterine-bladder interface and/or turbulent placental lacunae on color Doppler. All MRI studies were blindly evaluated by a single operator. PAS was defined as clinically significant when histopathological diagnosis was associated with at least one of: intrauterine balloon placement, compressive uterine sutures, peripartum hysterectomy, uterine or hypogastric artery ligature, uterine artery embolization.

RESULTS

A total of 39 women were included: 7/39 had clinically significant PAS. There were 6/18 cases of PAS with anterior placenta: hypoechoic space interruption and placental lacunae were the most sensitive sonographic signs (83%), while abnormal hyperechoic interface was the most specific (83%). On MRI, focal myometrial interruption and T2 intraplacental dark bands showed the best sensitivity (83%), bladder tenting had the best specificity (100%). 1/21 women with posterior placenta had PAS. There was substantial agreement between US and MRI in patients with anterior placenta (κ=0.78).

CONCLUSIONS

US and MRI agreement in antenatal diagnosis of clinically significant PAS was maximal in high-risk women. Placental lacunae on ultrasound scan and T2 intraplacental hypointense bands on MRI should trigger the suspicion of PAS.

Performance comparison of ultrasonography and magnetic resonance imaging in their diagnostic accuracy of placenta accreta spectrum disorders: a systematic review and meta-analysis

OBJECTIVES

Accurate prenatal diagnosis of placenta accrete spectrum disorder (PAS) remains a challenge, and the reported diagnostic value of ultrasonography (US) and magnetic resonance imaging (MRI) varies widely. This study aims to systematically evaluate the diagnostic accuracy of US as compared with MRI in the detection of PAS within the identical patient population.

METHODS

Medline, EMBASE, Google scholar and Cochrane library were searched. Pooled sensitivity, specificity, diagnostic odds ratio (DOR) and the area under the summary receiver operating characteristic (SROC) curve were calculated. Subgroup analysis was also performed to elucidate the heterogeneity of results.

RESULTS

A total of 18 articles comprising 861 pregnancies were included in the study. The overall diagnostic accuracy of US for identification of PAS was as follows: sensitivity [0.90 (0.86-0.93)], specificity [0.83 (0.79-0.86)], DOR [39.5 (19.6-79.7)]. The overall diagnostic accuracy of MRI for identification of PAS was as follows: sensitivity [0.89 (0.85-0.92)], specificity [0.87 (0.83-0.89)], DOR [37.4 (17.0-82.3)]. The pooled sensitivity (p = 0.808) and specificity (p = 0.413) between US and MRI are not significantly different. SROC analysis revealed that there was no statistical difference (p = 0.552) in US and MRI for the overall predictive accuracy of PAS. Furthermore, in the subgroup analysis of between retrospective and prospective studies, between earlier and most recent studies, there was no statistical difference (p > 0.05) in diagnostic accuracy of US and MRI for the detection of PAS.

CONCLUSIONS

Both ultrasonography (US) and magnetic resonance imaging (MRI) showed comparable accuracy in the prenatal diagnosis of placenta accrete spectrum disorder (PAS). Routine employment of MRI with relatively high expense in the prenatal identification of PAS should not be recommended.

Diagnostic performance of radiologists with different levels of experience in the interpretation of MRI of the placenta accreta spectrum disorder

OBJECTIVES

There have been no investigations on the association between previous abdominopelvic MRI experience without placental MRI experience and diagnostic accuracy of placenta accreta spectrum (PAS). To evaluate the diagnostic performance of radiologists with different experience levels in interpreting PAS-related MRI findings.

METHODS

This retrospective study included 60 women who underwent MRI for placental assessment between 2016 and 2020. MR images were reviewed by four radiologists who were blinded to the clinical outcomes and had different experience levels in interpreting PAS-related MRI findings. The radiologists' diagnostic performance was evaluated according to the pathologic and surgical outcomes. Simple κ statistics were calculated to determine agreement among the radiologists.

RESULTS

Of 60 women, 46 were diagnosed with PAS. The maternal age mean ± SD was 33.0 years ± 5.0 for the PAS absent group and 36.0 ± 4.3 for the PAS present group (p = 0.013). Overall, the most experienced radiologist had the highest sensitivity (100%, 95% confidence interval (CI): 92.3-100%) and NPV (100%, 95% CI: 63.1-100%) in PAS diagnoses. However, the PPV and specificity were independent of experience. The most experienced radiologist had the highest diagnostic accuracy in PAS (90%, 95% CI: 79.5-96.2%) and placenta percreta (95%, 95% CI: 86.1-99.0%). There was a strong association between definitive PAS diagnoses and the highest experience level. The κ values for the interobserver agreement regarding PAS diagnoses were 0.67 for the most experienced radiologist (p < 0.001) and 0.38, 0.40, and 0.43 for the other radiologists (p = 0.001) and regarding placenta percreta diagnoses were 0.87 for the senior radiologist (p < 0.001) and 0.63, 0.57, and 0.62 for the other radiologists (p < 0.001).

CONCLUSION

Previous experience in interpreting PAS-related MRI findings plays a significant role in accurately interpreting such imaging findings. Previous abdominopelvic MRI experience without specific placental MRI experience did not improve diagnostic performance.

ADVANCES IN KNOWLEDGE

We believe that our study makes a significant contribution to the literature and that this paper will be of interest to the readership of your journal because to the best of our knowledge, this study is the first in which the correlation between previous experience in abdominopelvic MRI with no specific experience in PAS-related MRI and diagnostic accuracy of radiologists has been explored. Our results could aid in setting up specialized multidisciplinary teams to assist women with PAS disorders.

Placenta Accreta Spectrum

Placenta accreta spectrum (PAS) refers to the range of pathologic adherence of the placenta to the uterine myometrium, including the placenta accreta, increta, and percreta. The incidence of PAS is rising primarily because of an increase in related risk factors, such as the rate of cesarean deliveries and pregnancies resulting from assisted reproductive technology. The maternal risks associated with PAS are significant, including hemorrhage, hysterectomy, and death. Fetal and neonatal risks are primarily the result of premature delivery. Antenatal diagnosis via ultrasonography and magnetic resonance imaging remains imperfect. Management of PAS varies, however, and there is a clear improvement in maternal outcomes with an antenatal diagnosis compared with unexpected diagnosis at the time of delivery. Studies that evaluate the balance between maternal and fetal/neonatal risks of expectant management versus preterm delivery have found that planned delivery between 34 and 35 weeks' gestation optimizes outcomes. Multidisciplinary PAS care teams have become the norm and recommended approach to management, given the complexity of caring for this obstetrical condition. Although significant advances have been made over the years, large knowledge gaps remain in understanding the pathophysiology, diagnosis, and clinical management.

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..

Circulating trophoblast cell clusters for early detection of placenta accreta spectrum disorders

Placenta accreta spectrum (PAS) is a high-risk obstetrical condition associated with significant morbidity and mortality. Current clinical screening modalities for PAS are not always conclusive. Here, we report a nanostructure-embedded microchip that efficiently enriches both single and clustered circulating trophoblasts (cTBs) from maternal blood for detecting PAS. We discover a uniquely high prevalence of cTB-clusters in PAS and subsequently optimize the device to preserve the intactness of these clusters. Our feasibility study on the enumeration of cTBs and cTB-clusters from 168 pregnant women demonstrates excellent diagnostic performance for distinguishing PAS from non-PAS. A logistic regression model is constructed using a training cohort and then cross-validated and tested using an independent cohort. The combined cTB assay achieves an Area Under ROC Curve of 0.942 (throughout gestation) and 0.924 (early gestation) for distinguishing PAS from non-PAS. Our assay holds the potential to improve current diagnostic modalities for the early detection of PAS.

Pregnancy-Related Hysterectomy for Peripartum Hemorrhage: A Literature Narrative Review of the Diagnosis, Management, and Techniques

Postpartum hemorrhage is a life-threatening situation, in which hysterectomy can be performed to prevent maternal death. However, it is associated with high rates of maternal morbidity and mortality and permanent infertility. The incidence of pregnancy-related hysterectomy varies across countries, but its main indications are the following: uterine atony and placenta spectrum (PAS) disorders. PAS disorder prevalence is rising during the last years, mainly due to the increased number of cesarean sections. As a result, obstetricians should be aware of the difficulties of this emergent condition and improve its accurate antenatal diagnosis rates, as well as its modern management strategies. Of course, special skills are required during a pregnancy-related hysterectomy, so these patients should be referred to centers of excellence in antenatal care, where a multidisciplinary team approach is followed. This study is a narrative review of the literature of the last 5 years (PubMed, Cochrane) regarding postpartum hemorrhage to offer obstetricians up-to-date knowledge on this pregnancy-related life-threatening issue. However, there is a lack of available high-quality data, because most published papers are retrospective case series or observational cohorts.

Accuracy and Interobserver Reliability of Magnetic Resonance Imaging for Placenta Accreta Spectrum Disorders

OBJECTIVE

This study aims to define the accuracy, predictive value, and interobserver reliability of magnetic resonance imaging (MRI) in the diagnosis of placenta accreta spectrum (PAS) disorders.

STUDY DESIGN

Two experienced radiologists independently interpreted the MRI studies of patients with possible PAS from two referral centers. Radiologists were blinded to sonographic and clinical information. We calculated diagnostic testing characteristics and kappa statistics of interobserver reliability for MRI findings of PAS.

RESULTS

Sixty-eight MRI cases were evaluated. Confirmed PAS and severe PAS were present in 44 (65%) and 20 (29%) cases. For the diagnosis of any PAS, MRI had a sensitivity 66%, specificity 71%, positive predictive value (PPV) 81%, negative predictive value (NPV) 53%, and accuracy 68%. For the diagnosis of severe PAS (percreta), MRI had a sensitivity 85%, specificity 79%, PPV 63%, NPV 93%, and accuracy 81%. The accuracy of individual signs of PAS was lower (44-65%). Interobserver agreement was almost perfect for previa; substantial for myometrial interruptions, PAS, severe PAS, and placental bulging/balling; and moderate to slight for other signs of PAS.

CONCLUSION

Although the interobserver reliability of MRI for a diagnosis of PAS is substantial, the accuracy and predictive value are modest and lower than previously reported.

Prediction of placenta accreta spectrum in patients with placenta previa using clinical risk factors, ultrasound and magnetic resonance imaging findings

OBJECTIVES

To predict placental accreta spectrum (PAS) in patients with placenta previa (PP) evaluating clinical risk factors (CRF), ultrasound (US) and magnetic resonance imaging (MRI) findings.

METHODS

Seventy patients with PP were retrospectively selected. CRF were retrieved from medical records. US and MRI images were evaluated to detect imaging signs suggestive of PAS. Univariable analysis was performed to identify CRF, US and MRI signs associated with PAS considering histology as standard of reference. Receiver operating characteristic curve (ROC) analysis was performed, and the area under the curve (AUC) was calculated. Multivariable analysis was also performed.

RESULTS

At univariable analysis, the number of previous cesarean section, smoking, loss of the retroplacental clear space, myometrial thinning < 1 mm, placental lacunae, intraplacental dark bands (IDB), focal interruption of myometrial border (FIMB) and abnormal vascularity were statistically significant. The AUC in predicting PAS progressively increased using CRF, US and MRI signs (0.69, 0.79 and 0.94, respectively; p < 0.05); the accuracy of MRI alone was similar to that obtained combining CRF, US and MRI variables (AUC = 0.97) and was significantly higher (p < 0.05) than that combining CRF and US (AUC = 0.83). Multivariable analysis showed that only IDB (p = 0.012) and FIMB (p = 0.029) were independently associated with PAS.

CONCLUSIONS

MRI is the best modality to predict PAS in patients with PP independently from CRF and/or US finding. It is reasonable to propose the combined assessment of CRF and US as the first diagnostic level to predict PAS, sparing MRI for selected cases in which US findings are uncertain for PAS.

Protrusion of placental tissue through the cervical os as an unusual presentation of placenta accreta: A case report

Introduction

Abnormal placentation commonly occurs in women with a history of uterine surgery or placenta previa. Placenta accreta spectrum can occur in the setting of lesser-known risk factors and anatomical locations.

Case

A 41-year-old woman (G6P4014) at 18 weeks of gestation without major risk factors was diagnosed with a placenta accreta after presenting for desired termination of pregnancy. On examination, placental tissue was found to be protruding through the cervical os and this was confirmed by magnetic resonance imaging (MRI). Management included pregnancy termination with intracardiac potassium chloride injection, uterine artery embolization, and a total abdominal hysterectomy.

Conclusion

Protruding cervical tissue should raise suspicion for placenta accreta. Appropriate evaluation and surgical planning should be performed to ensure a safe delivery.

•

Placenta accreta can occur in a patient without traditional risk factors.

•

Placenta acreeta should be considered when protruding cervical tissue is suspected or identified during pregnancy

•

The role of advanced maternal age in abnormal placentation should be further characterized.

•

Institutions should utilize a standard screening protocol for abnormal placentation including indications for MRI.

•

A multidisciplinary approach is critical to optimize maternal safety.

Correlation of placental MR imaging signs and pathologic diagnosis of placenta accreta spectrum: Retrospective single center case series

INTRODUCTION

Alongside initial screening obstetric US, use of placental MRI has been increasing in the last few decades to aid with antenatal diagnosis and delivery planning in Placenta Accreta Spectrum (PAS). The aim of this study was to determine if the MRI pathophysiological sign subcategories described in the current literature can predict the severity of pathologic diagnosis.

METHODS

Institutional imaging records were reviewed for placental MRIs performed for suspicion of PAS in the last decade. Electronic health records were searched for patient history and pathology. The 59 MRI studies were reviewed using the 11 MRI signs described by the SAR and ESUR joint consensus statement. Further breakdown of the signs was divided by underlying pathophysiologic subcategories including gross morphologic, interface and tissue architecture signs.

RESULTS

Pathologic diagnosis yielded 34 cases: accreta 4/34, incerta 14/34, percreta 10/34 and normal 6/34. Of the accreta cases all of them demonstrated at least two interface and half of the cases had tissue architecture signs, 13/14 increta cases demonstrated interface signs and 12/14 demonstrated tissue architecture signs, 9/10 percreta cases had two interface and at least six demonstrated three tissue architecture signs. Statistical analysis showed significant difference between pathologic diagnosis and the number of positive interface signs with p = 0.02.

DISCUSSION

Interface signs were the most objective and sensitive MRI subcategory. Statistical analysis determined there was a significant difference between PAS diagnosis and number of interface signs present. This subcategory has the most overlap with classic US signs which are traditionally used before MRI referral.

Role of Ultrasound and MRI in Diagnosis of Severe Placenta Accreta Spectrum Disorder: An Intraindividual Assessment With Emphasis on Placental Bulge

Background: The placental bulge sign (focal area of myometrial-placental bulging beyond the normal uterine contour) on ultrasound (US) or MRI is postulated to represent deeper venous invasion in placental accreta spectrum (PAS) disorder and may represent severe PAS. Objective: To evaluate the diagnostic performance and interobserver agreement of US and MRI features for diagnosis of severe PAS, with an emphasis on the placental bulge sign. Method: This retrospective study included 62 pregnant women (mean age 33.2±5.5 years) with clinically suspected PAS who underwent both US and MRI. Five independent reviewers (two maternal-fetal medicine specialists for US; three abdominal radiologists for MRI) independently reviewed images for the given modality, blinded to the final diagnosis, and recorded presence of a range of findings (nine on US, eight on MRI) including placental bulge. Intraoperative and pathologic findings were used to separate patients into those with and without severe PAS, based on International Federation of Gynaecology and Obstetrics classification. Diagnostic performance of US and MRI findings for severe PAS were evaluated; multivariable logistic regression was performed; and interobserver agreement was assessed. Results: A total of 58.1% (36/62) of patients had severe PAS. On US, the finding with highest accuracy for severe PAS was placental bulge (85.5%), which was associated with sensitivity of 91.7% and specificity of 76.9%. On MRI, the finding with highest accuracy was also placental bulge (90.3%), which was associated with sensitivity of 94.4% and specificity of 84.6%. At multivariable regression, placental bulge was an independent predictor of severe PAS for US [odds ratio (OR)=8.94; p=.02] and MRI (OR=45.67; p=.003). Interobserver agreement analysis demonstrated kappa for placental bulge of 0.48 for MRI and 0.40 for US. Given wide 95% CIs, differences among features for a given modality as well as differences between modalities were not statistically significant. Conclusion: The findings suggest strong performance of placental bulge in diagnosing severe PAS on both US and MRI, with potentially relatively stronger performance on MRI. Nonetheless, interobserver agreement remains suboptimal on both modalities. Clinical impact: Accurate prenatal diagnosis of severe PAS by imaging could help guide maternal counseling and selection between hysterectomy and uterine-preserving surgery.

Performance of antenatal imaging to predict placenta accreta spectrum degree of severity

Introduction

In cases of placenta accreta spectrum, a precise antenatal diagnosis of the suspected degree of invasion is essential for the planning of individual management strategies at delivery. The aim of this work was to evaluate the respective performances of ultrasonography and magnetic resonance imaging for the antenatal assessment of the severity of placenta accreta spectrum disorders included in the database. The secondary objective was to identify descriptors related to the severity of placenta accreta spectrum disorders.

Material and methods

All the cases included in the database for which antenatal imaging data were available were analyzed. The rates of occurrence of each ultrasound and magnetic resonance imaging descriptor were reported and compared between the Group “Accreta‐Increta” (FIGO grades 1 & 2) and the Group “Percreta” (FIGO grade 3).

Results

Antenatal imaging data were available for 347 women (347/442, 78.5%), of which 105 were included in the Group “Accreta – Increta” (105/347, 30.2%) and 213 (213/347, 61.4%) in the Group “Percreta”. Magnetic resonance imaging was performed in addition to ultrasound in 135 women (135/347, 38.9%). After adjustment for all ultrasound descriptors in multivariate analysis, only the presence of a bladder wall interruption was associated with a significant higher risk of percreta (Odds ratio 3.23, Confidence interval 1.33–7.79). No magnetic resonance imaging sign was significantly correlated with the degree of severity.

Conclusions

The performance of ultrasound and magnetic resonance imaging to discriminate mild from severe placenta accreta spectrum disorders is very poor. To date, the benefit of additional magnetic resonance imaging has not been demonstrated.

The clinical utility of magnetic resonance imaging as an adjunct to ultrasound in the diagnosis of placenta accreta spectrum disorders

OBJECTIVES

To determine if the use of magnetic resonance imaging (MRI) changes the diagnosis of placenta accreta spectrum (PAS) made on prenatal ultrasound (US) leading to an improvement in clinical outcomes.

METHODS

This was a retrospective chart review of all patients with evidence of PAS on US from 2012 to 2018 in one tertiary care medical center with subsequent use of MRI of the uterus to confirm diagnosis. The type of PAS classified by imaging was compared between US and MRI, with a final diagnosis made using histology. Outcomes that were analyzed included the following: 1) MRI correctly changed diagnosis, 2) MRI incorrectly downgraded diagnosis, 3) MRI incorrectly upgraded diagnosis, and 4) MRI did not change diagnosis. A T-test and Chi-squared test were performed to compare the clinical outcomes of patients with an upgraded diagnosis by MRI to those whose diagnosis was downgraded or stayed the same.

RESULTS

Forty-one patients received an MRI to validate the diagnosis of PAS after ultrasound and are included in the analysis. MRI changed the diagnosis in 36.6% (15/41) patients, correctly changing the diagnosis in 22% (9/41) and incorrectly upgrading the diagnosis in 14.6% (6/41). Patients whose diagnosis was upgraded by MRI (either correctly or incorrectly) were more likely to deliver earlier compared to those who were either downgraded or had no change in their diagnosis [33. 2 ± 3. 5 weeks vs 35. 2 ± 2. 9 weeks, p = 0.05]. Patients who were upgraded were more likely to have interventional radiology and/or urology involvement at the time of delivery [91.7% (11/12) vs 25. 9% (7/27), p = 0.001]. There were no complications from these procedures.

CONCLUSION

The use of MRI incorrectly changed the diagnosis as much as it correctly changed the diagnosis of PAS after US. MRI should not be used routinely as a clinical adjunct to ultrasound in the diagnosis of placenta accreta spectrum.

Placenta accreta spectrum disorder: updates on anesthetic and surgical management strategies

Placenta accreta spectrum (PAS) is a leading contributor to major obstetric hemorrhage and severe maternal morbidity in the developed world. In the United States, PAS has become the most common cause of peripartum hysterectomy. Over the last 40 years, clinicians have also witnessed a dramatic increase in the incidence of PAS. In the 1950s, the incidence of PAS was reported to be 0.03 per 1000 pregnancies. Recent epidemiological studies estimate that the PAS incidence is between 0.79 and 3.11 in 1000 pregnancies. As a consequence, obstetric anesthesiologists are increasingly likely to be called upon to manage women with suspected PAS for delivery. Given the increasing incidence and the morbidity burden associated with PAS, anesthesiologists play a vital role in optimizing maternal outcomes for women with PAS. This review will provide up-to-date information on nomenclature, pathophysiology, risk factors, antenatal detection, systemic preparations (includes timing of delivery, location of surgery, pre-operative evaluation and patient positioning), surgical and anesthetic approach, intra-operative management, invasive radiology and postoperative plans.

An Ultrasound Scoring Model for the Prediction of Intrapartum Morbidly Adherent Placenta and Maternal Morbidity: A Cross-Sectional Study

OBJECTIVE

 To design an ultrasound scoring model for the prediction of the intrapartum morbidly adherent placenta (MAP) and maternal morbidity.

PATIENTS AND METHODS

 114 females with singleton pregnancies ≥ 28 weeks of gestation referred for suspicion of MAP were included. All patients underwent examination by two-dimensional ultrasound with the color Doppler setting. Five signs were evaluated: the retroplacental echolucent space, placental lacunae, the hyperechoic uterine-bladder interface, retroplacental myometrium thickness, and subplacental, uterine serosa-bladder wall, intraplacental and bladder wall vascularity. We designed a score ranging from 0-8.5 points, including the five signs according to their odds ratios and evaluated its prediction for MAP and maternal morbidity.

RESULTS

 Using multivariate logistic regression, all ultrasound signs were significant dependent predictors for both MAP and maternal morbidity (myometrium thickness < 1 mm followed by lacunae ≥ 4 and lost retroplacental echolucent space). The only independent predictors for MAP were myometrium thickness < 1 mm and lacunae ≥ 4, while myometrium thickness < 1 mm and lost retroplacental echolucent space were predictive for maternal morbidity. The score showed a perfect agreement with MAP and a good one for maternal morbidity.

CONCLUSION

 Application of the score we designed can improve the ultrasound diagnosis of MAP and the maternal outcome.

Comparative analysis of ultrasound and MRI in the diagnosis of placenta accreta spectrum

OBJECTIVES

Placenta accreta spectrum constitutes one of the most complicated challenges in modern obstetrics. Given the conflicting data regarding the added value of MRI in the diagnosis of invasive placentation, we aim to assess individual and combined ability of multiple sonographic and MRI signs to diagnose placenta accreta spectrum in suspected cases.

METHODS

We assessed 28 cases of suspected placenta accreta spectrum in the third trimester. All cases underwent ultrasound assessment as well as MRI scan. Diagnosis was confirmed during surgery. The value of sonographic and MRI signs in the detection of placenta accreta spectrum was assessed.

RESULTS

A total of 23 cases were diagnosed with placenta accreta spectrum during cesarean delivery. Overall, ultrasound was found to be more sensitive and specific compared to MRI (sensitivity of 0.96 and specificity of 0.6 in ultrasound vs. sensitivity of 0.83 and specificity of 0.4 in MRI). However, the use of a post-hoc structured model improved MRI performance to a similar level of ultrasound (sensitivity of 0.96 and specificity of 0.6).

CONCLUSIONS

Ultrasound is superior to MRI in the detection of placenta accreta spectrum. However, MRI performance can be greatly improved by the use of a structured scoring system.

Placenta Accreta Spectrum Disorders: Challenges, Risks, and Management Strategies

The worldwide incidence of placenta accreta spectrum (PAS) is rapidly increasing, following the trend of rising cesarean delivery. PAS is an heterogeneous condition associated with a high maternal morbidity and mortality rate, presenting unique challenges in its diagnosis and management. So far, the rarity of this condition, together with the absence of high quality evidence and the lack of a standardized approach in reporting PAS cases for the ultrasound, clinical, and pathologic diagnosis, represented the main challenges for a deep understanding of this condition. The study of the available management strategies of PAS has been hampered by the heterogeneity of the available epidemiological data on this condition. The aim of this review is to provide a critical view of the current available evidence on the screening, the diagnosis, and the management options for PAS disorders, with a special focus on the challenges we foresee for the near future.

Prevention of postpartum hemorrhage

Postpartum hemorrhage is a leading cause of severe maternal morbidity and mortality worldwide and the United States. While the rates of maternal mortality attributable to hemorrhage are declining, severe maternal morbidity continues to be a growing problem. Efforts in recent years to more appropriately identify patients at risk, define significant hemorrhage, quantify blood loss, and standardize approaches to care in pregnancy and postpartum have led to an increasing preventability of PPH. We aim to review the most current recommendation for the prevention and effective management of obstetric hemorrhage.

The use of magnetic resonance imaging to predict placenta previa with placenta accreta spectrum

INTRODUCTION

Massive hemorrhage due to placenta previa with placenta accreta spectrum is associated with high maternal mortality and morbidity. Therefore, accurate prediction of placenta previa with placenta accreta spectrum is essential; magnetic resonance imaging (MRI) is a useful tool for this purpose. This study investigated novel predictors of anterior and posterior placenta previa with placenta accreta spectrum using MRI.

MATERIAL AND METHODS

This was a retrospective study at a tertiary obstetrics hospital in Japan. The singleton patients with placenta previa who were scanned with MRI prenatally and had a cesarean section at our institution between 2007 and 2018 were included. The prediction of anterior and posterior placenta previa with placenta accreta spectrum was evaluated using four MRI findings: heterogeneous signals in the placenta, dark T2-weighted intraplacental bands, myometrial thinning or interruption, and focal uterine bulging. The prediction of posterior placenta previa with placenta accreta spectrum was performed using the quantification of cervical varicosities, which were defined as the ratio of the distance between the minimum distance from the most dorsal cervical varicosities (a) to the deciduous and amniotic placenta (b) on a sagittal image.

RESULTS

Among 202 patients, 14 (6.9%) patients were pathologically diagnosed as having placenta accreta spectrum. Further, 38 (18.8%) patients had anterior placenta previa and 164 (81.2%) patients had posterior placenta previa. When anterior placenta previa with placenta accreta spectrum was predicted using at least one of the four MRI findings, the sensitivity and specificity of the anterior placenta previa with placenta accreta spectrum were 87.5% and 86.7%, respectively. In contrast, the sensitivity and specificity of posterior placenta previa with placenta accreta spectrum were 42.9% and 96.2%, respectively. But when the A/B ratio was set at 0.20, the sensitivity and specificity of the prediction for posterior placenta previa with placenta accreta spectrum using cervical varicosities were 100.0% and 89.2%, respectively.

CONCLUSIONS

The findings of MRI to predict the anterior placenta previa with placenta accreta spectrum were different from posterior placenta previa. The cervical varicosities may be useful in predicting posterior placenta previa with placenta accreta spectrum.