Assessment of total placenta previa by magnetic resonance imaging and ultrasonography to detect placenta accreta and its variants

Diagnostic accuracy of ultrasound in the diagnosis of Placenta accreta spectrum: systematic review and meta-analysis

OBJECTIVE

To evaluate the diagnostic accuracy of ultrasound and in the diagnosis of Placenta accreta spectrum (PAS).

DATA SOURCES

Screening of MEDLINE, CENTRAL, other bases from inception to February 2022 using the keywords related to placenta accreta, increta, percreta, morbidly adherent placenta, and preoperative ultrasound diagnosis.

STUDY ELIGIBILITY CRITERIA

All available studies- whether were prospective or retrospective- including cohort, case control and cross sectional that involved prenatal diagnosis of PAS using 2D or 3D ultrasound with subsequent pathological confirmation postnatal were included. Fifty-four studies included 5307 women fulfilled the inclusion criteria, PAS was confirmed in 2025 of them.

STUDY APPRAISAL AND SYNTHESIS METHODS

Extracted data included settings of the study, study type, sample size, participants characteristics and their inclusion and exclusion criteria, Type and site of placenta previa, Type and timing of imaging technique (2D, and 3D), severity of PAS, sensitivity and specificity of individual ultrasound criteria and overall sensitivity and specificity.

RESULTS

The overall sensitivity was 0.8703, specificity was 0.8634 with -0.2348 negative correlation between them. The estimate of Odd ratio, negative likelihood ratio and positive likelihood ratio were 34.225, 0.155 and 4.990 respectively. The overall estimates of loss of retroplacental clear zone sensitivity and specificity were 0.820 and 0.898 respectively with 0.129 negative correlation. The overall estimates of myometrial thinning, loss of retroplacental clear zone, the presence of bridging vessels, placental lacunae, bladder wall interruption, exophytic mass, and uterovesical hypervascularity sensitivities were 0.763, 0.780, 0.659, 0.785, 0.455, 0.218 and 0.513 while specificities were 0.890, 0.884, 0.928, 0.809, 0.975, 0.865 and 0.994 respectively.

CONCLUSIONS

The accuracy of ultrasound in diagnosis of PAS among women with low lying or placenta previa with previous cesarean section scars is high and recommended in all suspected cases.

TRIAL REGISTRATION

Number CRD42021267501.

Diagnosis of placenta accreta spectrum in high-risk women using ultrasonography or magnetic resonance imaging: systematic review and meta-analysis

OBJECTIVES

To perform a systematic review and meta-analysis of the diagnostic test accuracy of ultrasound and magnetic resonance imaging (MRI) and compare the performance of the two modalities in the diagnosis of placenta accreta spectrum (PAS).

METHODS

This was a systematic review conducted following the Cochrane Diagnostic Test Accuracy Reviews guideline. A literature search was performed in five databases: PubMed, EMBASE, PMC, The Cochrane Library and BVS-Bireme between 27 July and 4 August 2020. The search was updated on 18 August 2021. We included observational studies evaluating diagnostic accuracy in women with risk factors for PAS who had undergone both ultrasound and MRI examinations, published in English between 2011 and 2021. Quality Assessment of Diagnostic Accuracy Studies-2 was used to evaluate the quality of the studies. Forest plots for sensitivity and specificity with 95% CIs and receiver-operating-characteristics curves for ultrasound and MRI were constructed.

RESULTS

The literature search identified 266 studies. After reviewing the titles and abstracts of the articles, 51 were selected for full-text review and 17 studies including 1301 women with MRI and ultrasound data available were selected for the meta-analysis. The study population included 457 cases with PAS diagnosed using the gold standard method (intraoperative or histopathological analysis). The overall quality of the evaluated studies was considered satisfactory according to QUADAS-2. The meta-analysis revealed a sensitivity of 0.833 (95% CI, 0.776-0.878) and specificity of 0.834 (95% CI, 0.746-0.897) for ultrasound. For MRI, sensitivity was 0.838 (95% CI, 0.786-0.879) and specificity was 0.831 (95% CI, 0.770-0.878). There was no statistically significant difference between the two modalities. The Cochran's Q values indicated a high level of heterogeneity of sensitivity and specificity of ultrasound and MRI across studies.

CONCLUSIONS

Ultrasound and MRI have similar accuracy in the diagnosis of PAS. These results suggest that, in a setting with a high prevalence of risk factors, the choice of imaging modality for initial screening for PAS should depend on the availability of equipment and the examiner's expertise. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Shear-wave elastography for detection of placenta percreta: a case-controlled study

BACKGROUND

Prenatal diagnosis of placenta percreta (PP) is important to be able to provide effective management and a multidisciplinary approach to minimize the complications.

PURPOSE

To evaluate the role of shear-wave elastography (SWE) in the prenatal diagnosis of PP.

MATERIAL AND METHODS

A total of 18 women with PP and 20 pregnant women with normal placenta in the second or third trimesters were included in this prospective study. SWE was used to determine the elasticities of the placenta (in the maternal edge of the placenta) and myometrium. The obstetric data regarding grayscale and Doppler ultrasonography, and perinatal outcomes were reviewed. A mean placental SW velocity (SWV) cut-off value was determined to predict the presence of placental adherence.

RESULTS

The SWV values of the PP group in the maternal edge of the placenta were significantly higher than those of the control group (1.95 ± 0.19 m/s and 1.69 ± 0.23 m/s; P = 0.001). Myometrial SWV was also higher in the PP group compared to the control group (2.25 ± 0.39 m/s and 1.90 ± 0.71 m/s; P = 0.002). A receiver operating characteristic (ROC) curve analysis was performed and the best cut-off value of placental SWV was determined as 1.92 m/s with sensitivity of 58% and specificity of 80%, to predict the placental adherence in patients with PP.

CONCLUSION

Placental stiffness was significantly higher in patients with PP than in pregnant women with normally localized placenta. Thus, we thought that SWE of the placenta might be used as an alternative method in the diagnosis of PP.

Special Report of the Society for Maternal-Fetal Medicine Placenta Accreta Spectrum Ultrasound Marker Task Force: Consensus on definition of markers and approach to the ultrasound examination in pregnancies at risk for placenta accreta spectrum

Placenta accreta spectrum includes the full range of abnormal placental attachment to the uterus or other structures, encompassing placenta accreta, placenta increta, placenta percreta, morbidly adherent placenta, and invasive placentation. The incidence of placenta accreta spectrum has increased in recent years, largely driven by increasing rates of cesarean delivery. Prenatal detection of placenta accreta spectrum is primarily made by ultrasound and is important to reduce maternal morbidity associated with the condition. Despite a large body of research on various placenta accreta spectrum ultrasound markers and their screening performance, inconsistencies in the literature persist. In response to the need for standardizing the definitions of placenta accreta spectrum markers and the approach to the ultrasound examination, the Society for Maternal-Fetal Medicine convened a task force with representatives from the American Institute of Ultrasound in Medicine, the American College of Obstetricians and Gynecologists, the American College of Radiology, the International Society of Ultrasound in Obstetrics and Gynecology, the Society for Radiologists in Ultrasound, the American Registry for Diagnostic Medical Sonography, and the Gottesfeld-Hohler Memorial Ultrasound Foundation. The goals of the task force were to assess placenta accreta spectrum sonographic markers on the basis of available data and expert consensus, provide a standardized approach to the prenatal ultrasound evaluation of the uterus and placenta in pregnancies at risk of placenta accreta spectrum, and identify research gaps in the field. This manuscript provides information on the Placenta Accreta Spectrum Task Force process and findings.

In-vitro fertilisation-embryo-transfer complicates the antenatal diagnosis of placenta accreta spectrum using MRI: a retrospective analysis

AIM

To evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) for the antenatal diagnosis of placenta accreta spectrum (PAS).

MATERIALS AND METHODS

Data from 95 patients with placenta previa or low-lying placenta who underwent MRI at Osaka University Hospital for the antenatal diagnosis of PAS between January 2013 and December 2018 were reviewed retrospectively. The antenatal MRI signs suggesting PAS were assessed. Patients were divided into two groups depending on whether they were diagnosed with PAS. Factors that affected PAS diagnosis were identified using multivariate analysis.

RESULTS

The diagnostic accuracy of MRI for detecting PAS was as follows: 71.4% sensitivity, 96.4% specificity, and area under the curve (AUC) of 0.839 (95% confidence interval [CI]: 0.73-0.91). The diagnostic accuracy was lower in patients with in-vitro fertilisation with embryo transfer (IVF-ET): 22.2% sensitivity, 93.3% specificity, and AUC=0.578 (95% CI: 0.417-0.724). On multivariate analysis, only IVF-ET showed a significant association with false-positive or -negative MRI diagnosis of PAS (adjusted odds ratio: 26.5; 95% CI: 2.42-289.4; p=0.007).

CONCLUSION

IVF-ET affects the antenatal diagnosis of PAS using MRI.

ACR Appropriateness Criteria® Placenta Accreta Spectrum Disorder

Placenta accreta spectrum disorder (PASD) is the current terminology recommended by the International Federation of Obstetrics and Gynecology (FIGO) and should replace terms such as abnormally adherent/invasive placenta or morbidly adherent placenta. PASD refers to a variety of potential clinical complications, which may result from abnormal placental implantation. More specifically, placenta accreta refers to a defect in the decidua basalis where the chorionic villi adhere directly to the myometrium with trophoblastic invasion. Accurate antenatal diagnosis is needed to plan for an appropriate delivery strategy at an experienced center in order to reduce maternal and potential fetal morbidity and mortality. Obtaining radiologic and clinical data when PASD is first suspected can play a significant role in formulating an appropriate delivery strategy. Depending on the clinical risk factors and initial imaging findings, transabdominal ultrasound of the pregnant uterus with duplex Doppler and transvaginal ultrasound as needed are the most appropriate imaging procedures. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

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

Abnormally invasive placenta (AIP) is used to describe a placenta that does not separate naturally after delivery and cannot be extirpated without causing abnormally high blood loss. Recently, the use of a standardized terminology for descriptors of AIP signs seen on ultrasound has been prosed but to date no such unified descriptors have been developed for magnetic resonance imaging (MRI). The purpose of this paper is to propose a unified terminology based on a consensus opinion from the members of the International Society for AIP (IS-AIP) that include obstetricians, gynecologists, radiologists, pathologists, anesthesiologists and basic science researchers. We assume that using these standardized MRI descriptors for AIP will be useful for clinical use, education, teaching and future research projects, thus assumably improving care of patients with this condition. In addition, using a uniform terminology for AIP should become the first step of a standardized MRI report.

Abnormal placentation: the role of MRI in diagnosis and therapeutic planning

AIM

To evaluate the role of magnetic resonance imaging (MRI) for diagnosis and therapeutic planning in patients with abnormal placentation (AP).

MATERIALS AND METHODS

Overall, 168 consecutive patients with suspected placenta previa and AP were referred for MRI before caesarean section (CS). The ability of MRI to properly detect and assess abnormal placentation was correlated with findings at CS, which were considered the reference standard diagnostic tool. For each patient, MRI was used to determine whether the AP was suitable for complete/incomplete delivery, hysterectomy, or conservative treatment. Treatment planning with MRI was prospectively compared with the actual treatment that had been carried out in each patient decided at CS.

RESULTS

Placenta previa was detected at MRI in 63 patients and AP in 105 patients; 16 patients had false-positive MRI findings, and three had false-negative findings. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRI compared to findings at CS were 88.9% (149 of 168), 96.7% (89 of 92), 78.9% (60 of 76), 84.8% (89 of 105), and 95.2% (60 of 63), respectively. Treatment planning could be correctly made on the basis of MRI with accuracy, sensitivity, specificity, PPV, and NPV of 97%, 100%, 92.6%, 95.2%, and 100%, respectively.

CONCLUSIONS

MRI offers high diagnostic accuracy in the detection of AP, and it may be helpful in the detailed planning of treatment.

Prenatal identification of invasive placentation using magnetic resonance imaging: systematic review and meta-analysis

OBJECTIVE

To assess systematically the performance of prenatal magnetic resonance imaging (MRI) in diagnosing the presence, degree and topography of disorders of invasive placentation and to explore the role of the different MRI signs in predicting these disorders. The diagnostic accuracy of ultrasound and MRI in the detection of invasive placentation was also compared.

METHODS

MEDLINE, EMBASE, CINAHL and The Cochrane Library, including The Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects and The Cochrane Central Register of Controlled Trials, were searched electronically utilizing combinations of the relevant medical subject heading terms, keywords and word variants for 'invasive placentation' and 'magnetic resonance imaging'. Only prospective studies reporting a diagnosis of invasive placentation at the time of MRI and retrospective studies in which the radiologist was blinded to the final results were included in the analysis. The MRI signs explored were: uterine bulging, heterogeneous signal intensity, dark intraplacental bands on T2 weighted sequences, focal interruption of the myometrium and tenting of the bladder. Summary estimates of sensitivity, specificity, positive and negative likelihood ratios (LR+, LR-) and diagnostic odds ratio (DOR) were based, depending on the number of studies, upon DerSimonian-Laird random-effect or hierarchical summary receiver-operating characteristics models.

RESULTS

A total of 18 studies involving 1010 pregnancies at risk for invasive placentation were included. The overall diagnostic accuracy of MRI in detecting the presence of invasive placentation was: sensitivity, 94.4% (95% CI, 86.0-97.9%); specificity, 84.0% (95% CI, 76.0-89.8%); LR+, 5.91 (95% CI, 3.73-9.39); LR-, 0.07 (95% CI, 0.02-0.18); DOR, 89.0 (95% CI, 22.8-348.1). MRI had a high predictive accuracy in assessing both the depth and topography of placental invasion. All five MRI signs showed good predictive accuracy in the diagnosis of disorders of invasive placentation. There was no difference in either the sensitivity (P = 0.24) or the specificity (P = 0.91) between ultrasound and MRI for the detection of invasive placentation.

CONCLUSIONS

Prenatal MRI is highly accurate in diagnosing disorders of invasive placentation. Ultrasound and MRI have comparable predictive accuracy. Large population-based studies are needed in order to assess whether ultrasound can predict the depth and topography of placental invasion as reliably as can MRI.

Accuracy of ultrasonography and magnetic resonance imaging in the diagnosis of placenta accreta

Purpose

To evaluate the accuracy of ultrasonography and magnetic resonance imaging (MRI) in the diagnosis of placenta accreta and to define the most relevant specific ultrasound and MRI features that may predict placental invasion.

Material and Methods

This study was approved by the institutional review board of the French College of Obstetricians and Gynecologists. We retrospectively reviewed the medical records of all patients referred for suspected placenta accreta to two university hospitals from 01/2001 to 05/2012. Our study population included 42 pregnant women who had been investigated by both ultrasonography and MRI. Ultrasound images and MRI were blindly reassessed for each case by 2 raters in order to score features that predict abnormal placental invasion.

Results

Sensitivity in the diagnosis of placenta accreta was 100% with ultrasound and 76.9% for MRI (P = 0.03). Specificity was 37.5% with ultrasonography and 50% for MRI (P = 0.6). The features of greatest sensitivity on ultrasonography were intraplacental lacunae and loss of the normal retroplacental clear space. Increased vascularization in the uterine serosa-bladder wall interface and vascularization perpendicular to the uterine wall had the best positive predictive value (92%). At MRI, uterine bulging had the best positive predictive value (85%) and its combination with the presence of dark intraplacental bands on T2-weighted images improved the predictive value to 90%.

Conclusion

Ultrasound imaging is the mainstay of screening for placenta accreta. MRI appears to be complementary to ultrasonography, especially when there are few ultrasound signs.