Retroplacental Clear Space Research Articles

Prediction of placenta accreta spectrum in patients with placenta previa using a clinical, US and MRI combined model: A retrospective study with external validation

PurposeTo build and validate a predictive model of placental accreta spectrum (PAS) in patients with placenta previa (PP) combining clinical risk factors (CRF) with US and MRI signs. MethodOur retrospective study included patients with PP from two institutions. All patients underwent US and MRI examinations for suspicion of PAS. CRF consisting of maternal age, cesarean section number, smoking and hypertension were retrieved. US and MRI signs suggestive of PAS were evaluated. Logistic regression analysis was performed to identify CRF and/or US and MRI signs associated with PAS considering histology as the reference standard. A nomogram was created using significant CRF and imaging signs at multivariate analysis, and its diagnostic accuracy was measured using the area under the binomial ROC curve (AUC), and the cut-off point was determined by Youden’s J statistic. ResultsA total of 171 patients were enrolled from two institutions. Independent predictors of PAS included in the nomogram were: 1) smoking and number of previous CS among CRF; 2) loss of the retroplacental clear space at US; 3) intraplacental dark bands, focal interruption of the myometrial border and placental bulging at MRI. A PAS-prediction nomogram was built including these parameters and an optimal cut-off of 14.5 points was identified, showing the highest sensitivity (91%) and specificity (88%) with an AUC value of 0.95 (AUC of 0.80 in the external validation cohort). ConclusionA nomogram-based model combining CRF with US and MRI signs might help to predict PAS in PP patients, with MRI contributing more than US as imaging evaluation.

Role of magnetic resonance imaging in the diagnosis of placenta accreta.

To analyze the value of magnetic resonance imaging (MRI) in suspicious cases for prenatal detection of placenta accreta (PA). A total of 50 placental MRI exams performed on a 1.5T scanner were retrospectively reviewed by two radiologists in consensus.HASTE(half-Fourier acquisition single-shot turbo spin echo)and True-FISP (true fast imaging with steady-state precession) sequences were acquired. Findings from MRI were compared with the final diagnosis, which was determined by clinical findings at delivery and pathological examination of specimens. Of 50 pregnant women in the analysis, 33 required cesarean hysterectomy, and 17 underwent cesarean delivery.MRI signs such as myometrial thinning, loss of T2 hypointense interface(loss of retroplacental clear space on US), heterogenous intraplacental sign, and intraplacental T2 dark bands were more likely to be seen in this group. In this group, the cases that were finally clinically and pathologically confirmed were 12, 16, and 22 cases of placenta accreta vera, placenta increta, and placenta percreta respectively. MRI is particularly useful in cases where US is inconclusive and to assess the extent to which the placenta penetrates the uterine serosa and invades outward into surrounding tissues.MRI has become a routine examination for patients with suspected PA in clinical practice.

Nanoparticle Contrast-enhanced MRI for Visualization of Retroplacental Clear Space Disruption in a Mouse Model of Placental Accreta Spectrum (PAS)

Prior preclinical studies established the utility of liposomal nanoparticle blood-pool contrast agents in visualizing the retroplacental clear space (RPCS), a marker of normal placentation, while sparing fetuses from exposure because the agent does not cross the placental barrier. In this work, we characterized RPCS disruption in a mouse model of placenta accreta spectrum (PAS) using these agents. Contrast-enhanced MRI (CE-MRI) and computed tomography (CE-CT) using liposomal nanoparticles bearing gadolinium (liposomal-Gd) and iodine were performed in pregnant Gab3-/- and wild type (WT) mice at day 16 of gestation. CE-MRI was performed on a 1T scanner using a 2D T1-weighted sequence (100×100×600 µm3 voxels) and CE-CT was performed at a higher resolution (70×70×70 µm3 voxels). Animals were euthanized post-imaging and feto-placental units (FPUs) were harvested for histological examination. RPCS conspicuity was scored through blinded assessment of images. Pregnant Gab3-/- mice showed elevated rates of complicated pregnancy. Contrast-enhanced imaging demonstrated frank infiltration of the RPCS of Gab3-/- FPUs. RPCS in Gab3-/- FPUs was smaller in volume, demonstrated a heterogeneous signal profile, and received lower conspicuity scores than WT FPUs. Histology confirmed in vivo findings and demonstrated staining consistent with a thinner RPCS in Gab3-/- FPUs. Imaging of the Gab3-/- mouse model at late gestation with liposomal contrast agents enabled in vivo characterization of morphological differences in the RPCS that could cause the observed pregnancy complications. An MRI-based method for visualizing the RPCS would be valuable for early detection of invasive placentation.

VP44.20: Experience of a multidisciplinary team for management on placenta accreta spectrum disorders: ultrasound findings and clinical outcomes

Placenta accreta spectrum (PAS) disorders are among the leading causes of maternal morbimortality. The prenatal diagnosis of PAS disorder by ultrasound (US) allows multidisciplinary planning in an attempt to minimise the risk of maternal or neonatal morbidity and mortality. The aim of this study was to review cases of PAS focusing on US signs and comparing it with the surgical or histopathological findings. Retrospective analysis including all cases of PAS diagnosed between January 2018 and June 2021. After publications of FIGO guidelines on PAS disorders, a dedicated team was set up in order to optimise maternal and neonatal outcomes. For each case, US signs were reviewed according with 2018 FIGO guidelines and it was compared with surgical or histopathological findings. All the seven cases of PAS disorder treated in our centre during this period had a prenatal diagnosed. All women had a previous Caesarean birth and five had placenta previa. Regarding the US signs, myometrial thinning and loss of retroplacental clear space were described in all cases of PAS; vascular lacunae was present in six cases. Subplacental hypervascularisation was detected in four and uterovesical hypervascularisation and bridging vessels in three cases. Bladder wall interruption and placental bulge were observed only in two cases, both described as placenta percreta. Of the seven cases of PAS, three were considered placenta percreta according with US signs, but during surgery just two had the diagnose confirmed. Of the four cases with the diagnosis of placenta increta by US, two of them had surgical criteria of percreta. Regarding surgical approach, in all cases balloon occlusion catheters as placed in internal iliac and conservative management was possible in one case of placenta increta. There were no cases of maternal or neonatal death. In all cases, US signs of PAS disorder were present. Accurate prenatal diagnosis and multidisciplinary team approach have contributed to reduced adverse maternal and neonatal outcomes.

ROLE OF COLOR DOPPLER U/S AND MRI FOR DIAGNOSIS OF PLACENTA ACCRETA

Background: The worldwide incidence of placenta accreta (PA) is rapidly rising, following the trend of increasing cesarean delivery. Antenatal diagnosis is highly desirable because outcomes are optimized when delivery occurs at a level III or IV maternal care facility before the onset of labor and with avoidance of placental disruption. The primary diagnostic modality for antenatal diagnosis is obstetric color Doppler ultrasonography (CDUS). Magnetic Resonance Imaging (MRI), although widely employed, has yet to clearly demonstrate a significant improvement in management, but it is expensive and requires expertise that is rarely available in most low-income countries and many medium income countries. Objective: To evaluate and compare the accuracy of CDUS and MRI in the diagnosis of PA and to define the most relevant specific features that may predict placental invasion. Patients and methods: A case control study was conducted at AL- Azhar University Hospitals during the interval between November 2017 and November 2020, total set of 50 patients in the third trimester of pregnancy with diagnosis of placenta accreta and at least one previous caesarean section (CS). Patients were equally divided into 2 groups; Group I: Control group diagnosed as PA by CDUS. Group II: Study group diagnosed as placenta accreta by CDUS and subjected to MRI. With inclusion and exclusion criteria, all included women was subjected to; history taking, physical examination, obstetric CDUS and MRI scan was added for Group II only to pick up features suggestive of PA. Results: The sensitivity and specificity of CDUS were 100% and 72%, whereas the sensitivity and specificity of MRI were 76% and 52%, respectively, in their ability to diagnose PA. The highest sensitivity of individual CDUS and MRI markers in predicting PA were obliteration of the retroplacental clear space (63.6%) and focal interruption in the myometrial wall (73.7%), respectively. 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 or if there is a suspicion for invasion into surrounding organs.

Ultrasound as a Sole Modality for Prenatal Diagnosis of Placenta Accreta Spectrum: Potentialities and Pitfalls.

Background Placenta accreta spectrum (PAS) is a significant cause of maternal and neonatal mortality and morbidity. Its prevalence has been rising considerably, primarily due to the increasing rate of primary and repeat cesarean sections. Accurate prenatal identification of PAS allows optimal management because the timing of delivery, availability of blood products, and recruitment of skilled anesthesia, and surgical team can be arranged in advance. Aims and Objectives This study aimed to (1) study the ultrasound and color Doppler features of PAS, (2) correlate imaging findings with clinical and per-operative/histopathological findings, and (3) evaluate the accuracy of ultrasound for the diagnosis of PAS in patients with previous cesarean section. Materials and Methods This prospective study was conducted in radiology department of a tertiary care hospital. After screening 1,200 pregnant patients, 50 patients of placenta previa with period of gestation ≥ 24 weeks and history of at least one prior cesarean section were included in the study. Following imaging features were evaluated: (1) gray scale covering intraplacental lacunae, disruption of uterovesical interface, myometrial thinning, loss of retroplacental clear space, and focal exophytic masses; and (2) color Doppler covering intraplacental lacunar flow, hypervascularity of uterine serosa–bladder wall interface, and perpendicular bridging vessels between placenta and myometrium. Study Design Present study is a prospective one in a tertiary care hospital. Results Of the 19 PAS cases, 18 were correctly diagnosed on ultrasonography (USG) and confirmed either by histopathological analysis of hysterectomy specimen or per-operatively due to difficulty in placental removal. PAS was correctly ruled out in 27 of 31 patients. The diagnostic accuracy of USG was 90%. The sensitivity, specificity, positive, and negative predictive values were 94.7, 87.1, 81.8, and 96.4%, respectively. Conclusion Ultrasound is indispensable for the evaluation of pregnant patients. It is an important tool for diagnosing PAS, thereby making the operating team more cautious and better equipped for difficult surgery and critical postoperative care. It can be relied upon as the sole modality to accurately rule out PAS in negative patients, thereby obviating unnecessary psychological stress among patients due to possible hysterectomy.

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

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. 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. At univariable analysis, the number of previous cesarean section, smoking, loss of the retroplacental clear space, myometrial thinning < 1mm, 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. 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.

Diagnostic Value of Ultrasonography and MR in Antenatal Diagnosis of Placenta Accreta Spectrum

AbstractThe aim of this study was to compare the accuracy of ultrasonography and magnetic resonance imaging (MR) in the antenatal diagnosis of placenta accreta. We also determined the most relevant sonographic and MR features associated with the diagnosis of placenta accreta. In a prospective observational study approved by the Ethical Board of the Radiology Department, 109 pregnant women who were at high risk for Placenta Accreta were enrolled. The placentas of all cases were scanned using both gray-scale and color Doppler transabdominal sonography. MR was performed when sonographic findings were equivocal or inconclusive. The sonographic and MR features were compared with the final pathologic or clinical findings. The sensitivity and specificity were calculated for both sonography and MR. The role of each sonographic and MR feature was calculated by logistic regression. P &lt; 0.05 was considered as the significance level. The sensitivity and specificity of ultrasonography for the diagnosis of Placenta Accreta spectrum were 87% and 85% (P &lt; 0.001), while those of MR were 100% and 42% (P = 0.1), respectively. In ultrasonography, myometrium thickness ≤ 1 mm with a sensitivity of 83% (95 CI: 0.765, 0.927) and loss of retroplacental clear space with a sensitivity of 81% (95 CI: 0.755, 0.920) had the best sensitivity for the detection of the placental invasion. On MR, the heterogeneous signal intensity of placenta and uterine bulging with a sensitivity of 87% (95 CI: 0.698, 1.04) had the best sensitivity. Placenta accreta can be successfully detected prenatally using ultrasound. MR is useful in equivocal cases.

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

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

Natural embryonic death in the plain viscacha Lagostomus maximus: are there previous anatomo-histological variations that would intervene in the differential survival of the implantations?

Visualization of the retroplacental clear space (RPCS) may provide critical insight into the development of abnormally invasive placenta (AIP). In this pre-clinical study, we characterized the appearance of the RPCS on magnetic resonance imaging (MRI) during the second half of gestation using a liposomal gadolinium contrast agent (liposomal-Gd).Studies were performed in fifteen pregnant C57BL/6 mice at 10, 12, 14, 16, and 18 days of gestation. MRI was performed on a 1T permanent magnet scanner. Pre-contrast and post-contrast images were acquired using T1-weighted gradient-recalled echo (T1w-GRE) and T2-weighted fast spin echo (T2w-FSE) sequences. Animals were euthanized after imaging and feto-placental units harvested for histological examination. Visualization of the RPCS was scored by a maternal-fetal radiologist and quantified by measuring the contrast-to-noise ratio (CNR) on T1w images. Feto-placental features were segmented for analysis of volumetric changes during gestation.Contrast-enhanced T1w images enabled the visualization of structural changes in placental development between days 10–18 of gestation. Although the placental margin on the fetal side was clearly visible at all time points, the RPCS was partially visible at day 10 of gestation, and clearly visible by day 12. Hematoxylin and eosin (H&E) staining of the placental tissue corroborated MRI findings of structural and morphological changes in the placenta.Contrast-enhanced MR imaging using liposomal-Gd enabled adequate visualization of the retroplacental clear space starting at day 12 of gestation. The agent also enabled characterization of placental structure and morphological changes through gestation.

Pre-clinical magnetic resonance imaging of retroplacental clear space throughout gestation

IntroductionVisualization of the retroplacental clear space (RPCS) may provide critical insight into the development of abnormally invasive placenta (AIP). In this pre-clinical study, we characterized the appearance of the RPCS on magnetic resonance imaging (MRI) during the second half of gestation using a liposomal gadolinium contrast agent (liposomal-Gd). Materials and methodsStudies were performed in fifteen pregnant C57BL/6 mice at 10, 12, 14, 16, and 18 days of gestation. MRI was performed on a 1T permanent magnet scanner. Pre-contrast and post-contrast images were acquired using T1-weighted gradient-recalled echo (T1w-GRE) and T2-weighted fast spin echo (T2w-FSE) sequences. Animals were euthanized after imaging and feto-placental units harvested for histological examination. Visualization of the RPCS was scored by a maternal-fetal radiologist and quantified by measuring the contrast-to-noise ratio (CNR) on T1w images. Feto-placental features were segmented for analysis of volumetric changes during gestation. ResultsContrast-enhanced T1w images enabled the visualization of structural changes in placental development between days 10–18 of gestation. Although the placental margin on the fetal side was clearly visible at all time points, the RPCS was partially visible at day 10 of gestation, and clearly visible by day 12. Hematoxylin and eosin (H&E) staining of the placental tissue corroborated MRI findings of structural and morphological changes in the placenta. ConclusionsContrast-enhanced MR imaging using liposomal-Gd enabled adequate visualization of the retroplacental clear space starting at day 12 of gestation. The agent also enabled characterization of placental structure and morphological changes through gestation.

A comprehensive severity score for the morbidly adherent placenta: combining ultrasound and magnetic resonance imaging.

Ultrasound (US) is the first-line imaging modality to assess the morbidly adherent placenta, but sensitivity and specificity are lacking. This investigation aims to improve diagnostic accuracy with a comprehensive score using clinical history, US, and magnetic resonance imaging (MRI). We conducted a retrospective cohort study of pregnant women who received both transvaginal US and MRI with suspicion for morbidly adherent placenta between 2009 and 2016. US was scored with the following metrics: (i) previa, (ii) hypervascularity, (iii) loss of retroplacental clear space and (iv) lacunae. MRI was evaluated for (i) intraparenchymal vessels, (ii) abnormally dilated vessels, (iii) fibrin deposition, (iv) placental bulge and (v) bladder dome irregularity. Bayesian analysis was used to estimate the probability of morbidly adherent placenta for a given score. Diagnostic testing parameters were calculated. Among the 41 women with concerning imaging, histologically identified disease was confirmed in 16. The probability of morbidly adherent placenta increased with the score. At the highest US score, the probability of disease was 63.7%. With the highest MRI score, the probability of adherent placentation was 90.5%. Combining the US and MRI findings had a sensitivity of 56% and a specificity of 92%. A combined scoring system using MRI and US may accurately identify patients at risk for morbidity associated with morbidly adherent placenta.

Pre-clinical evaluation of a nanoparticle-based blood-pool contrast agent for MR imaging of the placenta

IntroductionNon-invasive 3D imaging that enables clear visualization of placental margins is of interest in the accurate diagnosis of placental pathologies. This study investigated if contrast-enhanced MRI performed using a liposomal gadolinium blood-pool contrast agent (liposomal-Gd) enables clear visualization of the placental margins and the placental-myometrial interface (retroplacental space). Non-contrast MRI and contrast-enhanced MRI using a clinically approved conventional contrast agent were used as comparators. Materials and methodsStudies were performed in pregnant rats under an approved protocol. MRI was performed at 1T using a permanent magnet small animal scanner. Pre-contrast and post-liposomal-Gd contrast images were acquired using T1-weighted and T2-weighted sequences. Dynamic Contrast enhanced MRI (DCE-MRI) was performed using gadoterate meglumine (Gd-DOTA, Dotarem®). Visualization of the retroplacental clear space, a marker of normal placentation, was judged by a trained radiologist. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated for both single and averaged acquisitions. Images were reviewed by a radiologist and scored for the visualization of placental features. Contrast-enhanced CT (CE-CT) imaging using a liposomal CT agent was performed for confirmation of the MR findings. Transplacental transport of liposomal-Gd was evaluated by post-mortem elemental analysis of tissues. Ex-vivo studies in perfused human placentae from normal, GDM, and IUGR pregnancies evaluated the transport of liposomal agent across the human placental barrier. ResultsPost-contrast T1w images acquired with liposomal-Gd demonstrated significantly higher SNR (p = 0.0002) in the placenta compared to pre-contrast images (28.0 ± 4.7 vs. 6.9 ± 1.8). No significant differences (p = 0.39) were noted between SNR in pre-contrast and post-contrast liposomal-Gd images of the amniotic fluid, indicating absence of transplacental passage of the agent. The placental margins were significantly (p < 0.001) better visualized on post-contrast liposomal-Gd images. DCE-MRI with the conventional Gd agent demonstrated retrograde opacification of the placenta from fetal edge to the myometrium, consistent with the anatomy of the rat placenta. However, no consistent and reproducible visualization of the retroplacental space was demonstrated on the conventional Gd-enhanced images. The retroplacental space was only visualized on post-contrast T1w images acquired using the liposomal agent (SNR = 15.5 ± 3.4) as a sharply defined, hypo-enhanced interface. The retroplacental space was also visible as a similar hypo-enhancing interface on CE-CT images acquired using a liposomal CT contrast agent. Tissue analysis demonstrated undetectably low transplacental permeation of liposomal-Gd, and was confirmed by lack of permeation through a perfused human placental model. ConclusionsContrast-enhanced T1w-MRI performed using liposomal-Gd enabled clear visualization of placental margins and delineation of the retroplacental space from the rest of the placenta; the space is undetectable on non-contrast imaging and on post-contrast T1w images acquired using a conventional, clinically approved Gd chelate contrast agent.

Diagnostic anténatal des placentas accreta : apport de l’échographie et de l’IRM dans une population à risque

Main objective was to compare accuracy of ultrasonography and MRI for antenatal diagnosis of placenta accreta. Secondary objectives were to specify the most common sonographic and RMI signs associated with diagnosis of placenta accreta. This retrospective study used data collected from all potential cases of placenta accreta (patients with an anterior placenta praevia with history of scarred uterus) admitted from 01/2010 to 12/2014 in a level III maternity unit in Strasbourg, France. High-risk patients beneficiated antenatally from ultrasonography and MRI. Sonographic signs registered were: abnormal placental lacunae, increased vascularity on color Doppler, absence of the retroplacental clear space, interrupted bladder line. MRI signs registered were: abnormal uterine bulging, intraplacental bands of low signal intensity on T2-weighted images, increased vascularity, heterogeneous signal of the placenta on T2-weighed, interrupted bladder line, protrusion of the placenta into the cervix. Diagnosis of placenta accreta was confirmed histologically after hysterectomy or clinically in case of successful conservative treatment. Twenty-two potential cases of placenta accreta were referred to our center and underwent both ultrasonography and MRI. All cases of placenta accreta had a placenta praevia associated with history of scarred uterus. Sensibility and specificity for ultrasonography were, respectively, 0.92 and 0.67, for MRI 0.84 and 0.78 without significant difference (p>0.05). The most relevant signs associated with diagnosis of placenta accreta in ultrasonography were increased vascularity on color Doppler (sensibility 0.85/specificity 0.78), abnormal placental lacunae (sensibility 0.92/specificity 0.55) and loss of retroplacental clear space (sensibility 0.76/specificity 1.0). The most relevant signs in MRI were: abnormal uterine bulging (sensitivity 0.92/specificity 0.89), dark intraplacental bands on T2-weighted images (sensitivity 0.83/specificity 0.80) or placental heterogeneity (sensitivity 0.92/specificity 0.89). Association of two sonographic or MRI signs had the best sensitivity/specificity ratio. Ultrasonography and RMI represent two interesting and complementary diagnostic tools for antenatal diagnosis of placenta accreta. Because of its cost and accessibility, ultrasonography remains the first in line to be used for diagnosis. Use of an analytical grid for diagnosis of placenta accreta could be helpful.

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

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

Accuracy of ultrasound for the prediction of placenta accreta

Ultrasound has been reported to be greater than 90% sensitive for the diagnosis of accreta. Prior studies may be subject to bias because of single expert observers, suspicion for accreta, and knowledge of risk factors. We aimed to assess the accuracy of ultrasound for the prediction of accreta. Patients with accreta at a single academic center were matched to patients with placenta previa, but no accreta, by year of delivery. Ultrasound studies with views of the placenta were collected, deidentified, blinded to clinical history, and placed in random sequence. Six investigators prospectively interpreted each study for the presence of accreta and findings reported to be associated with its diagnosis. Sensitivity, specificity, positive predictive, negative predictive value, and accuracy were calculated. Characteristics of accurate findings were compared using univariate and multivariate analyses. Six investigators examined 229 ultrasound studies from 55 patients with accreta and 56 controls for 1374 independent observations. 1205/1374 (87.7% overall, 90% controls, 84.9% cases) studies were given a diagnosis. There were 371 (27.0%) true positives; 81 (5.9%) false positives; 533 (38.8%) true negatives, 220 (16.0%) false negatives, and 169 (12.3%) with uncertain diagnosis. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 53.5%, 88.0%, 82.1%, 64.8%, and 64.8%, respectively. In multivariate analysis, true positives were more likely to have placental lacunae (odds ratio [OR], 1.5; 95% confidence interval [CI], 1.4-1.6), loss of retroplacental clear space (OR, 2.4; 95% CI, 1.1-4.9), or abnormalities on color Doppler (OR, 2.1; 95% CI, 1.8-2.4). Ultrasound for the prediction of placenta accreta may not be as sensitive as previously described.

Antenatal ultrasound assessment of placental/myometrial involvement in morbidly adherent placenta

To examine the usefulness of sonographic criteria in the assessment of the lateral extent and depth of myometrial involvement in morbidly adherent placenta. From hospital records and a perinatal database, women with morbidly adherent placenta confirmed at delivery and antenatal ultrasound assessment in 2004-2007 were identified. The sonographic appearance at the time of antenatal assessment was compared with the clinical and histological findings at delivery. Following statistical analysis, useful sonographic features in the assessment of myometrial invasion were identified. Nine cases, including one case of placenta percreta, eight cases of accreta or increta of which one minor partial, were reviewed. The criteria useful for the assessment of the lateral placental/myometrial involvement were obliteration of retroplacental clear space, increased subplacental vascularity, placental-tissue interface disruption and vessels crossing the interface disruption site with the last 2 signs applicable for helpful for assessment of the parametrium; and for the assessment of the depth, bladder serosa-uterine wall interface hypervascularity, vessels extending from placenta to bladder, placental-tissue interface disruption and vessels crossing placental-tissue interface disruption. The myometrial vascular pattern was also helpful in assessing the extensiveness of myometrial involvement. There was bulging of the lower uterine wall in the case of placenta percreta. Assessment of the placental/myometrial involvement of morbidly adherent placenta is possible on antenatal ultrasound examination. Combinations of different criteria may be required in assessing the lateral extent and the depth of placental/myometrial involvement.

Evaluation of sonographic diagnostic criteria for placenta accreta

To compare the diagnostic value of reported sonographic criteria for placenta accreta and to develop a composite score system for antenatal evaluation. Sixty-six women at risk for placenta accreta were examined for 9 cases of placenta accreta that were confirmed at delivery. The performance of previously reported gray-scale and Doppler sonographic criteria for the diagnosis of placenta accreta was analyzed individually. A composite score system was developed by combining selected sensitive or specific sonographic criteria, and its performance was evaluated. The criteria of obliteration of retroplacental clear space, a myometrial thickness of <1 mm, presence of vessels bridging placenta and uterine margin, disruption of the placental-uterine wall interface, and vessels crossing the sites of interface disruption showed a statistically significant association with placenta accreta. The disruption of the placental-uterine wall interface and the presence of vessels crossing these sites were the only 2 individual criteria that could distinguish placenta accreta from non-accreta, which could also be achieved by our composite score system using a cutoff value of 40, with a sensitivity of 89% and specificity of 98%. The diagnostic performance of the sonographic diagnostic criteria used in the diagnosis of placenta accreta varies, and a composite score system improves the overall accuracy.

The antenatal diagnosis of placenta accreta

The antenatal diagnosis of placenta accreta is invaluable in planning an approach to delivery or to management of an early intrauterine demise. The women most at risk are those who have had uterine surgery and have placenta previa, but placenta accreta can occur in any pregnancy. In early pregnancy the most useful ultrasound finding is implantation of the sac over a uterine scar. Vascular sinuses, appearing as early as 15 weeks, are irregularly shaped, have obvious blood flow when evaluated with color Doppler, and have the highest sensitivity for placenta accreta. Loss of the usual retroplacental clear space as a sole finding will usually be false positive. Magnetic resonance imaging diagnosis is in its infancy and has not yet been proven to add information unless the placenta is posterior. In the future it will hopefully aid in distinguishing placenta accreta from percreta.

The antenatal diagnosis of placenta accreta

The antenatal diagnosis of placenta accreta is invaluable in planning an approach to delivery or to management of an early intrauterine demise. The women most at risk are those who have had uterine surgery and have placenta previa, but placenta accreta can occur in any pregnancy. In early pregnancy the most useful ultrasound finding is implantation of the sac over a uterine scar. Vascular sinuses, appearing as early as 15 weeks, are irregularly shaped, have obvious blood flow when evaluated with color Doppler, and have the highest sensitivity for placenta accreta. Loss of the usual retroplacental clear space as a sole finding will usually be false positive. Magnetic resonance imaging diagnosis is in its infancy and has not yet been proven to add information unless the placenta is posterior. In the future it will hopefully aid in distinguishing placenta accreta from percreta.