A proposal for standardized magnetic resonance imaging (MRI) descriptors of abnormally invasive placenta (AIP) - From the International Society for AIP

Diagnostic accuracy of magnetic resonance imaging to predict peripartum hysterectomy and neonatal mortality in total placenta previa: A retrospective cohort study

OBJECTIVES

To assess the reliability of placental magnetic resonance imaging measurements in predicting peripartum hysterectomy and neonatal outcomes in patients with total placenta previa.

STUDY DESIGN

This retrospective cohort study, conducted at a single tertiary center, identified 372 pregnant women diagnosed with placenta previa. 277 singleton pregnancies that met the inclusion criteria and were diagnosed with total placenta previa in the third trimester were divided into two groups according to whether a placental MRI was performed. Two radiologists analyzed the MRI findings of 150 pregnant women with total placenta previa. Measurements were conducted for the placental volume of the upper and lower uterine sectors, cervical canal length, and cervical canal dilatation. A comparison was made between the surgical progression of these pregnant women and 127 pregnant women with total placenta previa who did not undergo an MRI. After pathological examination, 122 (63.2%) of 193 pregnant women diagnosed with placenta accreta spectrum underwent peripartum total abdominal hysterectomy. The results were compared using logistic regression analysis.

RESULTS

Reduced placental volume in the upper uterine segment and increased volume in the lower uterine segment significantly correlated with a higher probability of peripartum hysterectomy (cut-off: ≤343.4 and ≥ 403.4 cm3; OR: 0.993, 95 % CI: 0.990-0.995 and OR: 1.007, 95 % CI: 1.005-1.009, respectively). Shortened cervical canal length and increased dilatation raise the risk of peripartum hysterectomy (cut-off: ≤34, ≥11 mm; OR: 0.82, 95 % CI: 0.77 - 0.88 and OR: 1.7, 95 % CI: 1.4 - 2.1, respectively). The risk of neonatal death is 32 times higher in those < 34 weeks than in those 34 weeks or higher (95 % CI: 4.2-250, p = 0.001).

CONCLUSIONS

Placental MRI significantly contributes to predicting peripartum total abdominal hysterectomy and neonatal mortality in patients with total placenta previa associated with placenta accreta spectrum.

Can immunohistochemistry improve the pathological diagnosis of placenta accreta spectrum (PAS) disorders?

PURPOSE

The term of placenta accreta spectrum (PAS) disorder includes all grades of abnormal placentation. It is crucial for pathologist provide standardized diagnostic assessment to evaluate the outcome of management strategies. Moreover, a correct and safe diagnosis is useful in the medico-legal field when it becomes difficult for the gynecologist to demonstrate the suitability and legitimacy of demolitive treatment. The purposes of our study were: (1) to assess histopathologic features according to the recent guidelines; (2) to determine if immunohistochemistry can be useful to identify extravillous trophoblast (EVT) and to measure the depth of infiltration into the myometrium to improve the diagnosis of PAS.

METHODS

The retrospective study was conducted on 30 cases of gravid hysterectomy with histopathologic diagnosis of PAS. To identify the depth of EVT, immunohistochemical stainings were performed using anti MNF116 (cytokeratins 5, 6, 8, 17, 19), actin-SM, HPL (Human Placental Lactogen), vimentin and GATA3 antibodies.

RESULTS

Our cases were graded based on the degree of invasion of the myometrium. Ten were grade 1 (33.3%), 12 grade 2 (40%) and 8 grade 3A (26.7%). EVT invasion was best seen and evident by double immunostainings with actin-SM and cytokeratins, actin-SM and HPL, actin-SM and GATA3.

CONCLUSION

The role of pathologist is decisive to determine the different grades of PAS. A better understanding of the depth of myometrial invasion can be achieved by the use of immunohistochemistry affording an important tool to obtain reproducible grading of PAS. This purpose is crucial in the setting of postoperative quality reviews and particularly in the forensic medicine field.

Prediction of antenatal bleeding and preterm deliveries using placental magnetic resonance imaging in patients with placenta previa

PURPOSE

This study aimed to clarify associations between subacute hematoma on placental magnetic resonance imaging (MRI), antenatal bleeding, and preterm deliveries in patients with placenta previa (PP) without placenta accreta spectrum (PAS).

MATERIALS AND METHODS

This retrospective study investigated 78 consecutive patients with PP (median age, 34.5 years; interquartile range [IQR], 31-37 years) who underwent placental MRI in the third trimester. Patients with PAS detected intraoperatively or pathologically were excluded. Two radiologists evaluated the presence of subacute hematomas and their locations on placental MRI. We examined associations between presence of subacute hematoma and antenatal bleeding, emergency cesarean section (CS), hysterectomy, gestational age (GA) at delivery, birth weight, and amount of blood loss at CS. We also examined the association between perinatal outcome and subacute hematoma location: marginal, retro-placental, or intra-placental. Inter-observer agreement for the detection of subacute hematoma was calculated using kappa analysis.

RESULTS

Subacute hematomas were identified on MRI in 39 of the 78 patients (50.0%). Antenatal bleeding and emergency CS were more prevalent in patients with subacute hematoma on MRI (20 patients [51.3%] and 18 patients [46.2%], respectively) than in patients without (7 patients [17.9%], Fisher's exact test, p = 0.004 and 7 patients [17.9%], p = 0.014, respectively). GA at delivery was significantly lower in patients with subacute hematoma (median 36w3d, IQR 35w4d-37w1d) than in patients without (median 37w1d, IQR 36w4d-37w2d; Mann-Whitney test: p = 0.048). Marginal hematoma was significantly associated with antenatal bleeding and emergency CS. Inter-observer agreement for the presence of subacute hematoma was moderate (κ = 0.573).

CONCLUSION

Subacute hematoma on placental MRI was associated with antenatal bleeding, emergency CS and shorter GA at delivery in patients with PP. Marginal hematoma was also associated with antenatal bleeding and emergency CS. Placental MRI appears useful for predicting antenatal bleeding and preterm delivery in patients with PP.

[French survey on the management strategy for placenta accreta spectrum]

OBJECTIVE

Placenta accreta belongs to placenta accreta spectrum and is defined by an adhesion or even invasion of the placental villi in the myometrium. The main risk factor is a history of cesarean section. Its incidence is increasing following an increase in the cesarean section rate in recent years and the cause of severe maternal morbidity (hemorrhage, transfusions, hysterectomy). Treatment can be radical by cesarean section-hysterectomy or conservative with an attempt at uterine preservation. American, English, Canadian and international recommendations have been established but there are no French recommendations to date. The objective of this study was to investigate management strategy for placenta accreta in type III maternity hospitals in France.

MATERIALS AND METHODS

An anonymous questionnaire was sent by email to the obstetrics referents of the university hospital centers in France with type III maternity.

RESULTS

Forty-eight centers were approached, with a participation rate of 77%.

CONCLUSION

The management of placenta accreta spectrum in France is relatively heterogeneous on several points such as multidisciplinary management, evaluation by placental MRI, preoperative urological evaluation, treatment adopted as first-line, cesarean section-hysterectomy or conservative treatment, therapeutic strategy according to the placental invasion. However, the literature is currently poor, which may explain divergent treatment.

Primary and secondary postpartum haemorrhage: a review for a rationale endovascular approach

Postpartum haemorrhage (PPH) is a significant cause of maternal mortality globally, necessitating prompt and efficient management. This review provides a comprehensive exploration of endovascular treatment dimensions for both primary and secondary PPH, with a focus on uterine atony, trauma, placenta accreta spectrum (PAS), and retained products of conception (RPOC). Primary PPH, occurring within 24 h, often results from uterine atony in 70% of causes, but also from trauma, or PAS. Uterine atony involves inadequate myometrial contraction, addressed through uterine massage, oxytocin, and, if needed, mechanical modalities like balloon tamponade. Trauma-related PPH may stem from perineal injuries or pseudoaneurysm rupture, while PAS involves abnormal placental adherence. PAS demands early detection due to associated life-threatening bleeding during delivery. Secondary PPH, occurring within 24 h to 6 weeks postpartum, frequently arises from RPOC. Medical management may include uterine contraction drugs and hemostatic agents, but invasive procedures like dilation and curettage (D&C) or hysteroscopic resection may be required.Imaging assessments, particularly through ultrasound (US), play a crucial role in the diagnosis and treatment planning of postpartum haemorrhage (PPH), except for uterine atony, where imaging techniques prove to be of limited utility in its management. Computed tomography play an important role in evaluation of trauma related PPH cases and MRI is essential in diagnosing and treatment planning of PAS and RPOC.Uterine artery embolization (UAE) has become a standard intervention for refractory PPH, offering a rapid, effective, and safe alternative to surgery with a success rate exceeding 85% (Rand T. et al. CVIR Endovasc 3:1-12, 2020). The technical approach involves non-selective uterine artery embolization with resorbable gelatine sponge (GS) in semi-liquid or torpedo presentation as the most extended embolic or calibrated microspheres. Selective embolization is warranted in cases with identifiable bleeding points or RPOC with AVM-like angiographic patterns and liquid embolics could be a good option in this scenario. UAE in PAS requires a tailored approach, considering the degree of placental invasion. A thorough understanding of female pelvis vascular anatomy and collateral pathways is essential for accurate and safe UAE.In conclusion, integrating interventional radiology techniques into clinical guidelines for primary and secondary PPH management and co-working during labour is crucial.

Placental volume as a novel sign for identifying placenta accreta spectrum in pregnancies with complete placenta previa

BACKGROUND

Placenta accreta spectrum (PAS) carries an increased risk of maternal-fetal mortality and morbidity, and magnetic resonance imaging (MRI) features for PAS have been used for preoperative identification. This study aims to investigate the role of placental volume evaluated by MRI in identifying PAS in pregnant women with complete placenta previa.

METHODS

Totally 163 cases of complete placenta previa pregnant women with a history of cesarean section underwent MRI for suspected PAS were included. We categorized the patients into two groups according to the presence or absence of PAS, and the maternal-fetal perinatal outcomes and placental volume analyzed by 3D Slice software were compared.

RESULTS

There were significantly more gravidity, parity, and number of previous cesarean delivery in the PAS group (P < 0.05). Significant differences were also found between the two groups with respect to the following baseline characteristics: gestational age at delivery, intraoperative blood loss, blood transfusion, and neonatal birth weight (P < 0.05). Of 163 women in the study, 7 (4.294%) required cesarean hysterectomy for high-grade PAS or pernicious bleeding during cesarean section, and PAS was confirmed with histologic confirmation in 6 (85.714%) cases. The placental volume in PAS group was greater than that in the non-PAS group (P < 0.05). With a threshold of more than 887 cm3, the sensitivity and specificity in identifying PAS were 85.531% and 83.907% respectively, with AUC 0.908 (95% CI: 0.853-0.948).

CONCLUSIONS

Placental volume may be a promising indicator of PAS in complete placenta previa patients with a history of cesarean section.

Developments in functional imaging of the placenta

The placenta is both the literal and metaphorical black box of pregnancy. Measurement of the function of the placenta has the potential to enhance our understanding of this enigmatic organ and serve to support obstetric decision making. Advanced imaging techniques are key to support these measurements. This review summarises emerging imaging technology being used to measure the function of the placenta and new developments in the computational analysis of these data. We address three important examples where functional imaging is supporting our understanding of these conditions: fetal growth restriction, placenta accreta, and twin-twin transfusion syndrome.

The role of internal iliac artery intraoperative vascular clamp temporary occlusion in abnormally invasive placenta

OBJECTIVE

To investigate the efficacy of internal iliac artery intraoperative vascular clamp temporary occlusion in the treatment of abnormally invasive placenta.

METHOD

This retrospective study enrolled 153 patients diagnosed with abnormally invasive placenta between January 2018 and December 2021. The patients were divided into a study group (n = 88, undergoing cesarean section followed by internal iliac artery vascular clamp temporary occlusion) and a control group (n = 65, receiving routine cesarean section). The general situation, intraoperative conditions, postoperative complications, and neonatal outcomes were compared between the two groups.

RESULTS

The hysterectomy rate in the study group was significantly lower than that in the control group. However, there were no significant differences in intraoperative blood loss, blood transfusion, postoperative intensive care unit transfer rate, or neonatal outcome between the groups. Further subgrouping showed that in patients with placenta increta, the hysterectomy rate and intraoperative bleeding amount were significantly lower in the occlusion group. Nevertheless, these advantages were not significantly different between the groups in patients with placenta percreta.

CONCLUSION

Vascular clamp temporary occlusion of internal iliac artery is an effective method for controlling hemorrhage and decreasing the incidence of hysterectomy in patients with placenta increta. For patients with placenta percreta, the benefit is limited.

Bladder involvement in placenta accreta spectrum disorder with placenta previa: MRI findings and outcomes correlation

BACKGROUND

Placental accreta spectrum (PAS) disorder with bladder involvement can be associated with maternal and neonatal morbidity. Magnetic resonance imaging (MRI) may provide accurate preoperative diagnoses.

OBJECTIVE

This study had 2 aims: to retrospectively review the MRI findings for bladder involvement in PAS with placental previa and to correlate bladder involvement with maternal and neonatal outcomes.

MATERIALS AND METHODS

MRI images of 48 patients with severe PAS (increta and percreta) with placenta previa/low-lying placenta were evaluated by 2 experienced radiologists blinded to the final diagnoses. Nine MRI findings and stepwise logistic regression analysis were assessed to identify predictive MRI findings for bladder involvement. The correlations between PAS patients with bladder involvement and clinical outcomes were analyzed using Fisher's exact test.

RESULTS

Of the 48 patients, 27 did not have bladder involvement, while 21 did. Logistic regression analysis identified 2 predictive MRI features for bladder involvement. They were abnormal vascularization (OR,6.94; 95 %CI,1.05-45.75) and loss of the chemical shift line at the uterovesical interface (OR, 4.41; 95 %CI, 0.63-30.98). The sensitivity and specificity of the combined MRI features were 38.1 % and 100 %, respectively (p = 0.001). A significant correlation was found between bladder involvement and massive blood loss during surgery (p = 0.022).

CONCLUSIONS

PAS with bladder involvement was significantly correlated with massive surgical blood loss. Prenatally, the disorder was predicted with high specificity by the combination of loss of chemical shift artifacts in the steady-state free precession sequence and abnormal vascularization at the uterovesical interface on MRI.

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.

Comparison between 1.5-T and 3.0-T MRI for the diagnosis of placenta accreta spectrum disorders

PURPOSE

Accurate antenatal diagnosis of placenta accreta spectrum (PAS) is important for optimal management. The purpose of this study was to compare the respective capabilities of 1.5-T and 3.0-T MRI in the diagnosis of PAS.

MATERIALS AND METHODS

Between March 2016-March 2021, 190 pregnant women at high risk for PAS underwent dedicated prenatal MRI with either 1.5-T or 3.0-T units at a tertiary imaging center. Cesarian section and MRI were performed less than 6 weeks from each other. Prospectively collected data were evaluated by two experienced genitourinary radiologists for presence and extent of PAS. A comparative study was designed to investigate differences in predictive ability between 1.5-T and 3.0-T MRI groups. Sensitivity, specificity, accuracy, negative and positive prognostic values relative to intraoperative/histological findings, were computed for both groups and were compared with chi-square (χ 2) test. Interobserver agreement was estimated using Kappa test.

RESULTS

One hundred-eighty-two gravid women were included in the study; of these, 91/182 (50%) women were evaluated with 1.5-T (mean age, 35 ± 5.1 [SD] years; mean gestational age: 32.5 weeks) and 91/182 (50%) with 3.0-T MRI (mean age, 34.9 ± 4.9 [SD] years; mean gestational age, 32.1 weeks). 1.5-T MRI yielded 95.7% sensitivity (95% CI: 87.8-99.1) and 81.8% specificity (95% CI: 59.8) and 3.0-T MRI 93.8% sensitivity (95% CI: 86.0-97.9) and 83.3% specificity (95% CI: 48.2-97.7) for PAS identification, with no differences between the two groups (P = 0.725 and P >0.999, respectively). MRI showed excellent predictive ability for detecting extrauterine placental spread with 100% sensitivity (95% CI: 89.4-100.0), 96.7% specificity (95% CI: 88.1-99.6) for 1.5-T and 97% sensitivity (95% CI: 84.2-99.9), 96.7% specificity (95% CI: 88.1-99.6) for 3.0-T without differences between the two groups (P > 0.999). Interobserver agreement was excellent for both groups. The most frequently detected MRI signs of PAS for both 1.5-T and 3.0-T groups were placental heterogeneity (n = 85, 93.5% vs. n = 90, 98.9%; P = 0.413), and intraplacental fetal vessels (n = 64, 70.3% vs. n = 65, 71.4%; P = 0.870).

CONCLUSION

This study suggests that 3.0-T MRI and 1.5-T MRI are equivalent for the diagnosis 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.

Imaging during pregnancy: What the radiologist needs to know

During the last decades, there has been a growing demand for medical imaging in gravid women. Imaging of the pregnant woman is challenging as it involves both the mother and the fetus and, consequently, several medical, ethical, or legal considerations are likely to be raised. Theoretically, all currently available imaging modalities may be used for the evaluation of the pregnant woman; however, in practice, confusion regarding the safety of the fetus often results in unnecessary avoidance of useful diagnostic tests, especially those involving ionizing radiation. This review article is focused on the current safety guidelines and considerations regarding the use of different imaging modalities in the pregnant population; also presented is an imaging work-up for the most common medical conditions of pregnant women, with emphasis on fetal and maternal safety.

Diagnostic Utility of MRI Features of Placental Adhesion Disorder for Abnormal Placentation and Massive Postpartum Hemorrhage

OBJECTIVE. The study's aim was to assess MRI, in cases in which MRI was deemed clinically necessary, to determine its diagnostic accuracy for placental adhesion disorder (PAD) and prognostic accuracy for massive postpartum hemorrhage (PPH). Additionally, we investigated the diagnostic utility of MRI in the antenatal workup of PAD as an adjunct to clinical assessment and ultrasound. MATERIALS AND METHODS. We retrospectively identified patients who underwent antenatal MRI for suspicion of PAD. Images were reviewed by two radiologists who were blinded to surgical and pathologic outcomes. Diagnostic utility of various clinical, ultrasound, and MRI features of PAD were estimated by ROC analysis. Logistic regression analysis was performed to assess various diagnostic models for PAD and prognostic models for massive PPH, with model selection based on Bayesian information criterion. RESULTS. Fifty-six patients met the inclusion criteria. Sensitivity and specificity of MRI in the diagnosis of PAD were 93% and 81%, respectively. The most accurate MRI features for PAD were myometrial thinning (AUC = 0.881), heterogeneous placenta (AUC = 0.864), and placental bulge (AUC = 0.845). The most accurate MRI features for massive PPH were heterogeneous placenta (AUC = 0.872) and dark intraplacental bands (AUC = 0.736). The addition of MRI to a model based on clinical and ultrasound features was preferred for both diagnosis of PAD and prognosis of massive PPH. CONCLUSION. This study shows the utility of certain MRI features for identification of PAD and massive PPH. Furthermore, our data show a substantial incremental benefit of the addition of MRI in the antenatal workup for PAD compared with clinical assessment and ultrasound alone.

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.

When a rare condition creates a scientific society: The history of the International Society for Placenta Accreta Spectrum (IS-PAS)

Almost 10 years ago, clinicians at multiple locations all over Europe observed an increased number of antenatally undiagnosed cases of placenta accreta spectrum (PAS) resulting in significant morbidity and the occasional maternal death. Even with an improvement in antenatal imaging, the management of severe PAS remains challenging. One solution to improve understanding in rare but potentially lethal conditions is international collaboration. Consequently, a European working group was formed, which over the next few years grew into an international society, the IS-PAS. The collective goals are to develop a large shared database of cases, generate high-quality research into all aspects of PAS, and improve education of both healthcare professionals and patients. The first results of this collaboration are presented within this supplement.

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.

Intraplacental Fetal Vessel Diameter May Help Predict for Placental Invasiveness in Pregnant Women at High Risk for Placenta Accreta Spectrum Disorders

Background Prenatal identification of placenta accreta spectrum (PAS) disorder is essential for treatment planning. More objective means for predicting PAS and clinical outcome may be provided by MRI descriptors. Purpose To investigate the association of intraplacental fetal vessel (IFV) diameter at MRI with PAS and peripartum complications. Materials and Methods Between March 2016 and October 2019, 160 gravid women suspected of having PAS underwent placental MRI as part of a prospective trial. Secondary analysis was performed by two experienced genitourinary radiologists for presence and maximum diameter of IFVs. Relative risk ratios were computed to test the association of IFVs with presence and depth of PAS invasiveness. Receiver operating characteristic analysis was used to evaluate the ability of IFV diameter to help predict PAS, placenta percreta, and peripartum complications and for comparison of the area under the curve (AUC) versus that from other combined MRI predictors of PAS (eg, myometrial thinning, intraplacental T2-hypointense bands, uterine bulge, serosal hypervascularity, and signs of extrauterine placental spread). Intraoperative and histopathologic findings were the reference standard. Results A total of 155 women were evaluated (mean age, 35 years ± 5 [standard deviation]; mean gestational age, 32 weeks ± 3). PAS was diagnosed in 126 of 155 women (81%) (placental percreta in 68 of 126 [54%]). At delivery, 30 of 126 women (24%) experienced massive blood loss (>2000 mL). IFVs were detected at MRI in 109 of 126 women with PAS (86%) and in 67 of 68 women with placental percreta (98%). The relative risk ratio was 2.4 (95% CI: 1.6, 3.4; P < .001) for PAS and 10 (95% CI: 1.5, 70.4; P < .001) for placental percreta when IFVs were visible. IFVs of 2 mm or greater were associated with PAS (AUC, 0.81; 95% CI: 0.67, 0.95; P = .04). IVFs of 3 mm or greater were associated with placenta percreta (AUC, 0.81; 95% CI: 0.73, 0.89; P < .001) and with peripartum complications, including massive bleeding (AUC, 0.80; 95% CI: 0.71, 0.89; P < .001). Combining assessment of IFVs with other MRI descriptors improved the ability of MRI to predict PAS (AUC, 0.94 vs 0.89; P = .009). Conclusion Assessment of intraplacental fetal vessels with other MRI descriptors improved the ability of MRI to help predict PAS. Vessel diameter of 3 mm or greater was predictive of placenta percreta and peripartum complications. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Dighe in this issue.

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.

Minimizing surgical blood loss at cesarean hysterectomy for placenta previa with evidence of placenta increta or placenta percreta: the state of play in 2020

The evolution of multidisciplinary team-based care for women with placenta accreta spectrum disorder has delivered stepwise improvements in clinical outcomes. Central to this overall goal is the ability to limit blood loss at surgery. Placement of inflatable balloons within the pelvic arteries, most commonly in the anterior divisions of the internal iliac arteries, became popular in many centers, at the expense of prolonging surgical care and with attendant risks of vascular injury. In tandem, the need to expose pelvic sidewall anatomy to safely identify the course of the ureters re-popularized the alternative strategy of ligating the same anterior divisions of the internal iliac arteries. With incremental gains in surgical expertise, described in 5 steps in this review, our teams have witnessed a steady decline in surgical blood loss. Nevertheless, a subset of women has the most severe form of placenta accreta spectrum, namely placenta previa-percreta. Such women are at risk of major hemorrhage during surgery from vessels arising outside the territories of the internal iliac arteries. These additional blood supplies, mostly from the external iliac arteries, pose significant risks of major blood loss even in experienced hands. To address this risk, some centers, principally in China, have adopted an approach of routinely placing an infrarenal aortic balloon, with both impressively low rates of blood loss and an ability to conserve the uterus by resecting the placenta with the affected portion of the uterine wall. We review these literature developments in the context of safely performing elective cesarean hysterectomy for placenta previa-percreta, the most severe placenta accreta spectrum disorder.

A comparison of recent guidelines in the diagnosis and management of placenta accreta spectrum disorders

Accreta placentation and in particular its invasive forms are impacting maternal health outcomes globally and the prevalence of placenta accreta spectrum (PAS) continues to increase. The Royal College of Obstetricians and Gynaecologists (RCOG) and the American College of Obstetricians and Gynecologists (ACOG) with the Society for Maternal-Fetal Medicine (SMFM) have updated their national guidelines, whereas the Federation International of Gynecology and Obstetrics (FIGO) and the Society of Obstetricians and Gynecologists of Canada (SOGC) have developed new guidelines on the diagnosis and management of PAS. A comparison of these guidelines highlights common strong recommendations on the need to carefully evaluate women at high risk for PAS (e.g. prior uterine surgery presenting with anterior low-lying placenta or placenta previa), using multi-modal ultrasound imaging. For women diagnosed with PAS, multidisciplinary team-based care, with full logistic support structures (immediate access to comprehensive blood products, adult and neonatal intensive care) and established expertise in complex pelvic surgery, is critical to maximise safe outcomes for mothers and newborns.

The role of interventional radiology in the management of abnormally invasive placenta: a systematic review of current evidences

Abnormally invasive placenta (AIP) is a potentially severe condition. To date, arterial embolization in women with postpartum hemorrhage due to AIP is the treatment option for which highest degrees of evidence are available. However, other techniques have been tested, including prophylactic catheter placement, balloon occlusion of the iliac arteries and abdominal aorta balloon occlusion. In this systematic review, we provide an overview of the currently reported interventional radiology procedures that are used for the treatment of postpartum hemorrhage due to AIP and suggest recommendations based on current evidences. Owing to a high rate of adverse events, prophylactic occlusion of internal iliac arteries should be used with caution and applied when the endpoint is hysterectomy. On the opposite, when a conservative management is considered to preserve future fertility, uterine artery embolization should be the preferred option as it is associated with a hysterectomy rate of 15.5% compared to 76.5% with prophylactic balloon occlusion of the internal iliac arteries and does not result in fetal irradiation. Limited data are available regarding the application of systematic prophylactic embolization and no comparative studies with arterial embolization are available.

Society of Abdominal Radiology (SAR) and European Society of Urogenital Radiology (ESUR) joint consensus statement for MR imaging of placenta accreta spectrum disorders

OBJECTIVES

This study was conducted in order to establish the joint Society of Abdominal Radiology (SAR) and European Society of Urogenital Radiology (ESUR) guidelines on placenta accreta spectrum (PAS) disorders and propose strategies to standardize image acquisition, interpretation, and reporting for this condition with MRI.

METHODS

The published evidence-based data and the opinion of experts were combined using the RAND-UCLA Appropriateness Method and formed the basis for these consensus guidelines. The responses of the experts to questions regarding the details of patient preparation, MRI protocol, image interpretation, and reporting were collected, analyzed, and classified as "recommended" versus "not recommended" (if at least 80% consensus among experts) or uncertain (if less than 80% consensus among experts).

RESULTS

Consensus regarding image acquisition, interpretation, and reporting was determined using the RAND-UCLA Appropriateness Method. The use of a tailored MRI protocol and standardized report was recommended.

CONCLUSIONS

A standardized imaging protocol and reporting system ensures recognition of the salient features of PAS disorders. These consensus recommendations should be used as a guide for the evaluation of PAS disorders with MRI.

KEY POINTS

• MRI is a powerful adjunct to ultrasound and provides valuable information on the topography and depth of placental invasion. • Consensus statement proposed a common lexicon to allow for uniformity in MRI acquisition, interpretation, and reporting of PAS disorders. • Seven MRI features, namely intraplacental dark T2 bands, uterine/placental bulge, loss of low T2 retroplacental line, myometrial thinning/disruption, bladder wall interruption, focal exophytic placental mass, and abnormal vasculature of the placental bed, reached consensus and are categorized as "recommended" for diagnosing PAS disorders.