A novel MRI-based diagnostic model for predicting placenta accreta spectrum

Objective To develop and evaluate a diagnostic model based on MRI signs for predicting placenta accreta spectrum. Materials and Methods A total of 155 pregnant women were included in this study, randomly divided into 104 cases in the training set and 51 cases in the validation set. There were 93 Non-PAS cases, and 62 cases in the PAS group. The training set included 62 Non-PAS cases and 42 PAS cases. Clinical factors and MRI signs were collected for univariate analysis. Then, binary logistic regression analysis was used to develop independent diagnostic models with clinical relevant risk factors or MRI signs, as well as those combining clinical risk factors and MRI signs. The ROC curve analysis was used to evaluate the diagnostic performance of each diagnostic model. Finally, the validation was performed with the validation set. Results In the training set, four clinical factors (gestity, parity, uterine surgery history, placental position) and 11 MRI features (T2-dark bands, placental bulge, T2 hypointense interface loss, myometrial thinning, bladder wall interruption, focal exophytic mass, abnormal placental bed vascularization, placental heterogeneity, asymmetric placental thickening/shape, placental ischemic infarction, abnormal intraplacental vascularity) were considered as risk factors for PAS. The AUC of the clinical diagnostic model, MRI diagnostic model, and clinical + MRI model of PAS were 0.779, 0.854, and 0.874, respectively. In the validation set, the AUC of the clinical diagnostic model, MRI diagnostic model, and clinical + MRI model of PAS were 0.655, 0.728, and 0.735, respectively. Conclusion Diagnosis model based on MRI features in this study can well predict placenta accreta spectrum.

Diffusion-derived vessel density (DDVD) computed from a simple diffusion MRI protocol as a biomarker of placental blood circulation in patients with placenta accreta spectrum disorders: A proof-of-concept study

OBJECTIVES

Increasing trend of PAS (placenta accreta spectrum disorders) incidence is a major health concern as PAS is associated with high maternal morbidity and mortality during cesarean section. Prenatal identification of PAS is crucial for delivery planning and patients management. This study aims to explore whether diffusion-derived vessel density (DDVD) computed from a simple diffusion MRI protocol differs in PAS from normal placenta.

METHODS

We enrolled 86 patients with PAS disorders and 40 pregnant women without PAS disorders. Each patient underwent intravoxel incoherent motion (IVIM) MRI sequence with 11 b-values. Placenta diffusion-derived vessel density (DDVD-b0b50) was the signal difference between b = 0 and b = 50 s/mm2 images. DDVD(b0b50) A/N was calculated as [accreta lesion DDVD(b0b50)]/ [normal placenta DDVD(b0b50)]. The correlation between DDVD and gestational age was explored using Spearman rank correlation. Differences of DDVD(b0b50) A/N in patients with normal placentas and with PAS, and in patients with different subtypes of PAS were explored.

RESULTS

DDVD was negatively correlated with gestational age (p = 0.023, r = -0.359) in patients with normal placentas. DDVD(b0b50) A/N was significantly higher in patients with PAS (median:1.16, mean: 1.261) than normal placenta (median:1.02, mean: 1.032, p < 0.001) and especially higher in patients with placenta increta (median:1.14, mean: 1.278) and percreta (median: 1.20, mean: 1.396, p < 0.001).

CONCLUSION

As a higher DDVD indicates higher physiological volume of micro-vessels in PAS, this study suggests DDVD can be a potential biomarker to evaluate the placenta perfusion.

The value of the combined MR imaging features and clinical factors Nomogram model in predicting intractable postpartum hemorrhage due to placenta accreta

To explore the value of the combined MR imaging features and clinical factors Nomogram model in predicting intractable postpartum hemorrhage (IPH) due to placenta accreta (PA). We conducted a retrospective study with 270 cases of PA patients admitted to our hospital from January 2015 to December 2022. The clinical data of these patients were analyzed, and they were divided into 2 groups: the IPH group and the non-IPH group based on the presence of IPH. The differences in data between the 2 groups were compared, and the risk factors for IPH were analyzed. A Nomogram model was constructed using independent high-risk factors, and the predictive value of this model for IPH was analyzed. The results of multivariable binary Logistic regression analysis showed higher number of cesareans, placenta previa, placenta accreta type (implantation, penetration), low signal strip on T2 weighted image (T2WI) were independent high-risk factor for IPH (P < .05). ROC analysis and Hosmer-Lemeshow goodness-of-fit test showed the Nomogram predictive model constructed with the high-risk factor has good discrimination and calibration. Decision curve analysis (DCA) showed that when the probability threshold for the Nomogram model's prediction was in the range from 0.125 to 0.99, IPH patients could obtain more net benefits, making it suitable for clinical application. The higher number of cesareans, placenta previa, placental accreta type (implantation, penetration), and low signal strip on T2WI are independent high-risk factor for IPH. The Nomogram predictive model constructed with the high-risk factor demonstrates good clinical efficacy in predicting the occurrence of IPH due to PA.

Sensitivity of antenatal ultrasound in diagnosing posterior placenta accreta spectrum disorders

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Accuracy of MRI-Based Radiomics in Diagnosis of Placenta Accreta Spectrum: A PRISMA Systematic Review and Meta-Analysis

BACKGROUND Placenta accreta syndrome (PAS) can lead to severe obstetric bleeding, and can be life-threatening. This study aimed to assess the precision of radiomics features derived from magnetic resonance imaging (MRI) for diagnosing PAS. MATERIAL AND METHODS A comprehensive search was conducted in the databases PubMed, Embase, Web of Science, and the Cochrane library from inception to October 2023. We included diagnostic accuracy studies utilizing radiomics-MRI in PAS patients, with histopathology serving as the reference standard. The overall diagnostic odds ratio (DOR), sensitivity, specificity, and area under the curve (AUC) were computed to gauge the diagnostic accuracy of MRI-based radiomic features in PAS patients. Quality assessment was performed using the Quality Assessment of Diagnostic Accuracy Studies 2. Statistical analyses were carried out using Stata 14.2, MetaDiSc 1.4, and Review Manager 5.3 software. RESULTS Seven studies involving 672 patients were incorporated. The aggregated DOR, sensitivity, specificity, and AUC for radiomics in detecting PAS were 78% (confidence interval32, 191), 87% (76%, 93%), 92% (89%, 94%), and 0.93 (0.91-0.95), respectively. The meta-analysis revealed notable heterogeneity among the included studies, with no evidence of a threshold effect. Subgroup analysis demonstrated that, in comparison to manual segmentation and validation groups with ≤100 cases and internal validation datasets, automated segmentation, validation groups with >100 cases, and external validation datasets exhibited superior diagnostic performance . CONCLUSIONS Our findings indicate that MRI-based radiomic features perform well in assessing the diagnostic risk of PAS during prenatal diagnosis. This noninvasive and convenient tool may prove valuable in facilitating the identification of PAS.

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

BACKGROUND

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Placenta acrreta spectrum-first trimester, 2D and 3D ultrasound, and magnetic resonance imaging findings

BACKGROUND

The term placenta accreta spectrum (PAS) is commonly used to describe abnormal trophoblastic invasion of the myometrium, serosa, or organs adjacent to the uterus. It is of great obstetric importance because of its high morbidity, risk of hemorrhage, admission to the intensive care unit, risk of hysterectomy, and high risk of iatrogenic pelvic lesions and even death. These risks are minimized when prenatal diagnosis is performed. Prenatal diagnosis of PAS is based on imaging findings suggestive of abnormal and pathologically adherent placentation, including placental lacunae (intraplacental sonolucent spaces), disruption of the bladder-uterine serosa interface, turbulent flow on color Doppler, and bridging vessels.

OBJECTIVE

In this article, we review the major prenatal imaging features of PAS using diagnostic modalities (first trimester, two-dimensional ultrasound, three-dimensional ultrasound, and magnetic resonance imaging) for the diagnosis of PAS.

CT angiography for characterization of advanced placenta accreta spectrum: indications, risks, and benefits

Placenta accreta spectrum disorder (PASD) encompasses various types of abnormal placentation in which chorionic villi directly adhere to or invade the myometrium. The incidence of PASD has dramatically risen in the US over the past 3 decades owing to the increased rates of patients undergoing cesarean sections. While PASD remains a significant cause of maternal morbidity and mortality, accurate prenatal identification and characterization of PASD is associated with improved outcomes. Although ultrasound is the first-line imaging modality in the evaluation of PASD, with MRI serving as an adjunct, computed tomography angiography (CTA) may also offer unique diagnostic advantages in cases of advanced PASD by providing superior visualization of placental and abdominopelvic vasculature and enabling the creation of comprehensive vascular maps to roadmap complex surgical interventions. This paper represents the first evaluation of CTA as a diagnostic tool and operative planning aid in this context. Appropriate indications and diagnostic advantages of CTA in this setting are reviewed, and key multimodal imaging features of normal and abnormal placentation are highlighted.

Prenatal Diagnosis of Placenta Accreta Spectrum Disorders: Deep Learning Radiomics of Pelvic MRI

BACKGROUND

Diagnostic performance of placenta accreta spectrum (PAS) by prenatal MRI is unsatisfactory. Deep learning radiomics (DLR) has the potential to quantify the MRI features of PAS.

PURPOSE

To explore whether DLR from MRI can be used to identify pregnancies with PAS.

STUDY TYPE

Retrospective.

POPULATION

324 pregnant women (mean age, 33.3 years) suspected PAS (170 training and 72 validation from institution 1, 82 external validation from institution 2) with clinicopathologically proved PAS (206 PAS, 118 non-PAS).

FIELD STRENGTH/SEQUENCE

3-T, turbo spin-echo T2-weighted images.

ASSESSMENT

The DLR features were extracted using the MedicalNet. An MRI-based DLR model incorporating DLR signature, clinical model (different clinical characteristics between PAS and non-PAS groups), and MRI morphologic model (radiologists' binary assessment for the PAS diagnosis) was developed. These models were constructed in the training dataset and then validated in the validation datasets.

STATISTICAL TESTS

The Student t-test or Mann-Whitney U, χ2 or Fisher exact test, Kappa, dice similarity coefficient, intraclass correlation coefficients, least absolute shrinkage and selection operator logistic regression, multivariate logistic regression, receiver operating characteristic (ROC) curve, DeLong test, net reclassification improvement (NRI) and integrated discrimination improvement (IDI), calibration curve with Hosmer-Lemeshow test, decision curve analysis (DCA). P < 0.05 indicated a significant difference.

RESULTS

The MRI-based DLR model had a higher area under the curve than the clinical model in three datasets (0.880 vs. 0.741, 0.861 vs. 0.772, 0.852 vs. 0.675, respectively) or MRI morphologic model in training and independent validation datasets (0.880 vs. 0.760, 0.861, vs. 0.781, respectively). The NRI and IDI were 0.123 and 0.104, respectively. The Hosmer-Lemeshow test had nonsignificant statistics (P = 0.296 to 0.590). The DCA offered a net benefit at any threshold probability.

DATA CONCLUSION

An MRI-based DLR model may show better performance in diagnosing PAS than a clinical or MRI morphologic model.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.

Accuracy of Ultrasound in the Prediction of the FIGO Classification of Placenta Accreta Spectrum

OBJECTIVES

To evaluate the accuracy of greyscale ultrasound (US) and colour Doppler detecting placenta accreta spectrum (PAS) based on the newly recommended International Federation of Obstetrics and Gynaecology (FIGO) grading system.

METHODS

This prospective study was conducted on women diagnosed with placenta previa or low-lying placenta involving the anterior uterine wall and associated with PAS as identified by the US. Transabdominal and transvaginal greyscale US was performed on admission between 34 and 36 weeks of gestation and compared to clinical grading and histopathological examination after cesarean hysterectomy.

RESULTS

In total, 36 pregnant females who underwent a cesarean hysterectomy due to placenta previa complicated by PAS were included in this study. All patients had a history of previous cesarean deliveries, ranging from 1 to 5 deliveries. The US has an overall sensitivity of 33%, 55%, and 84.62%, and specificity of 100%, 75%, and 60% in detecting the 3 degrees of PAS, respectively. US cannot differentiate between the different subtypes of PAS grade 3 (a, b, and c).

CONCLUSION

The overall US evaluation was highly significant in predicting the FIGO diagnosis of PAS; however, all ultrasonographic signs were equally relevant in diagnosing grade 1 and/or 2 PAS and were inaccurate in differing the subtypes of PAS grade 3.

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

BACKGROUND

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

PURPOSE

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

STUDY TYPE

Retrospective.

SUBJECTS

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

FIELD STRENGTH/SEQUENCE

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

ASSESSMENT

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

STATISTICAL TESTS

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

RESULTS

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

DATA CONCLUSION

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

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

Deep Learning Model Based on Multisequence MRI Images for Assessing Adverse Pregnancy Outcome in Placenta Accreta

BACKGROUND

Preoperative assessment of adverse outcomes risk in placenta accreta spectrum (PAS) disorders is of high clinical relevance for perioperative management and prognosis.

PURPOSE

To investigate the association of preoperative MRI multisequence images and adverse pregnancy outcomes by establishing a deep learning model in patients with PAS.

STUDY TYPE

Retrospective.

POPULATION

323 pregnant women (age from 20 to 46, the median age is 33), suspected of PAS, underwent MRI to assess the PAS, divided into the training (N = 227) and validation datasets (N = 96).

FIELD STRENGTH/SEQUENCE

1.5T scanner/fast imaging employing steady-state acquisition sequence and single shot fast spin echo sequence.

ASSESSMENT

Different deep learning models (i.e., with single MRI input sequence/two sequences/multisequence) were compared to assess the risk of adverse pregnancy outcomes, which defined as intraoperative bleeding ≥1500 mL and/or hysterectomy. Net reclassification improvement (NRI) was used for quantitative comparison of assessing adverse pregnancy outcome between different models.

STATISTICAL TESTS

The AUC, sensitivity, specificity, and accuracy were used for evaluation. The Shapiro-Wilk test and t-test were used. A P value of <0.05 was considered statistically significant.

RESULTS

215 cases were invasive placenta accreta (67.44% of them with adverse outcomes) and 108 cases were non-invasive placenta accreta (9.25% of them with adverse outcomes). The model with four sequences assessed adverse pregnancy outcomes with AUC of 0.8792 (95% CI, 0.8645-0.8939), with ACC of 85.93% (95%, 84.43%-87.43%), with SEN of 86.24% (95% CI, 82.46%-90.02%), and with SPC of 85.62% (95%, 82.00%-89.23%) on the test cohort. The performance of model with four sequences improved above 0.10 comparing with that of model with two sequences and above 0.20 comparing with that of model with single sequence in terms of NRI.

DATA CONCLUSION

The proposed model showed good diagnostic performance for assessing adverse pregnancy outcomes.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY: Stage 2.

Placental lakes vs lacunae: spot the differences

Sonographic sonolucencies are anechoic areas surrounded by tissue of normal echogenicity, commonly found in the placental parenchyma during the second and third trimesters of pregnancy. The ultrasound appearance of lakes and lacunae derives from the low echogenicity of villous-free areas within the placental parenchyma, filled with maternal blood of varying velocities. In normal placentation, lakes usually start appearing as soon as maternal blood begins to flow freely within the intervillous space at the end of the first trimester, whereas, in accreta placentation, lacunae develop progressively during the second trimester. Larger lakes are found mainly in areas of lower villous density under the fetal plate or in the marginal areas, but can also be found in the center of a lobule above the entry of a spiral artery. Lakes of variable size, position and shape are of no clinical significance, except if they transform into echogenic cystic lesions, which have been associated with poor fetal growth and placental malperfusion. Lacunae are formed by the distortion of one or more placental lobules developing inside a uterine scar, resulting from high-volume, high-velocity flows from the radial/arcuate arteries, and are associated with a high probability of placenta accreta spectrum at birth. They often present with ultrasound signs of uterine remodeling following scarring. Lakes and lacunae can coexist within the same placenta and both will change in size and shape as pregnancy advances. Better understanding of the etiopathology of placental sonolucent spaces and associated morphological changes is necessary to identify patients at risk of subsequent complications during pregnancy and/or at delivery. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Development and validation of MRI-based scoring models for predicting placental invasiveness in high-risk women for placenta accreta spectrum

OBJECTIVES

To develop and validate MRI-based scoring models for predicting placenta accreta spectrum (PAS) invasiveness.

MATERIALS AND METHODS

This retrospective study comprised a derivation cohort and a validation cohort. The derivation cohort came from a systematic review of published studies evaluating the diagnostic performance of MRI signs for PAS and/or placenta percreta in high-risk women. The significant signs were identified and used to develop prediction models for PAS and placenta percreta. Between 2016 and 2021, consecutive high-risk pregnant women for PAS who underwent placental MRI constituted the validation cohort. Two radiologists independently evaluated the MRI signs. The reference standard was intraoperative and pathologic findings. The predictive ability of MRI-based models was evaluated using the area under the curve (AUC).

RESULTS

The derivation cohort included 26 studies involving 2568 women and the validation cohort consisted of 294 women with PAS diagnosed in 258 women (88%). Quantitative meta-analysis revealed that T2-dark bands, placental/uterine bulge, loss of T2 hypointense interface, bladder wall interruption, placental heterogeneity, and abnormal intraplacental vascularity were associated with both PAS and placenta percreta, and myometrial thinning and focal exophytic mass were exclusively associated with PAS. The PAS model was validated with an AUC of 0.90 (95% CI: 0.86, 0.93) for predicting PAS and 0.85 (95% CI: 0.79, 0.90) for adverse peripartum outcome; the placenta percreta model showed an AUC of 0.92 (95% CI: 0.86, 0.98) for predicting placenta percreta.

CONCLUSION

MRI-based scoring models established based on quantitative meta-analysis can accurately predict PAS, placenta percreta, and adverse peripartum outcome.

CLINICAL RELEVANCE STATEMENT

These proposed MRI-based scoring models could help accurately predict PAS invasiveness and provide evidence-based risk stratification in the management of high-risk pregnant women for PAS.

KEY POINTS

• Accurately identifying placenta accreta spectrum (PAS) and assessing its invasiveness depending solely on individual MRI signs remained challenging. • MRI-based scoring models, established through quantitative meta-analysis of multiple MRI signs, offered the potential to predict PAS invasiveness in high-risk pregnant women. • These MRI-based models allowed for evidence-based risk stratification in the management of pregnancies suspected of having PAS.

Determinants of emergency Cesarean delivery in pregnancies complicated by placenta previa with or without placenta accreta spectrum disorder: analysis of ADoPAD cohort

OBJECTIVES

To investigate the rate and outcome of emergency Cesarean delivery (CD) in women with placenta previa with or without placenta accreta spectrum disorders (PAS) and to elucidate the diagnostic accuracy of ultrasound in predicting emergency CD.

METHODS

This was a secondary analysis of a multicenter prospective study involving 16 referral hospitals in Italy (ADoPAD study). Inclusion criteria were women with placenta previa minor (< 20 mm from the internal cervical os) or placenta previa major (covering the os), aged ≥ 18 years, who underwent transabdominal and transvaginal ultrasound assessment at ≥ 26 + 0 weeks of gestation. The primary outcome was the occurrence of emergency CD, defined as the need for immediate surgical intervention performed for emergency maternal or fetal indication, including active labor, cumulative maternal bleeding > 500 mL, severe and persistent vaginal bleeding such that maternal hemodynamic stability could not be achieved or maintained, or category-III fetal heart rate tracing unresponsive to resuscitative measures. The primary outcome was reported separately in the population of women with placenta previa and no PAS confirmed after birth and in those with PAS. The secondary aim was to report on the strength of association and to test the diagnostic accuracy of ultrasound in predicting emergency CD. Univariate, multivariate and diagnostic accuracy analyses were used to analyze the data.

RESULTS

A total of 450 women, including 97 women with placenta previa and PAS and 353 with placenta previa only, were analyzed. In women with placenta previa and PAS, emergency CD was required in 20.6% (95% CI, 14-30%), and 60.0% (12/20) delivered before 34 weeks of gestation. The mean gestational age at delivery was 32.3 ± 2.7 weeks in women undergoing emergency CD and 34.9 ± 1.8 weeks in those undergoing elective CD (P < 0.001). Women undergoing emergency CD had a higher median estimated blood loss (2500 (interquartile range (IQR), 1350-4500) vs 1100 (IQR, 625-2500) mL; P = 0.012), mean units of blood transfused (7.3 ± 8.8 vs 2.5 ± 3.4; P = 0.02) and more frequent placement of a mechanical balloon (50.0% vs 16.9%; P = 0.002) compared with those undergoing elective CD. On univariate analysis, the presence of interrupted retroplacental space, interrupted bladder line and placental lacunae was more common in women not experiencing emergency CD. No comprehensive multivariate analysis could be performed in this subgroup of women. Ultrasound signs of PAS, including presence of interrupted retroplacental space, interrupted bladder line and placental lacunae, were not predictive of emergency CD. In women with placenta previa but no PAS, emergency CD was required in 31.2% (95% CI, 26.6-36.2%), and 32.7% (36/110) delivered before 34 weeks of gestation. The mean gestational age at delivery was lower in women undergoing emergency CD compared with those undergoing elective CD (34.2 ± 2.9 vs 36.7 ± 1.6 weeks; P < 0.001). Pregnancies complicated by emergency CD were associated with a lower birth weight (2330 ± 620 vs 2800 ± 480 g; P < 0.001) and had a higher risk of need for blood transfusion (22.7% vs 10.7%; P = 0.003) compared with those who underwent elective CD. On multivariate analysis, only placental thickness (odds ratio (OR), 1.02 (95% CI, 1.00-1.03); P = 0.046) and cervical length < 25 mm (OR, 3.89 (95% CI, 1.33-11.33); P = 0.01) were associated with emergency CD. However, a short cervical length showed low diagnostic accuracy for predicting emergency CD in these women.

CONCLUSION

Emergency CD occurred in about 20% of women with placenta previa and PAS and 30% of those with placenta previa only and was associated with worse maternal outcome compared with elective intervention. Prenatal ultrasound is not predictive of the risk of emergency CD in women with these disorders. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

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.

Diagnostic Role of Cell-Free miRNAs in Identifying Placenta Accreta Spectrum during First-Trimester Screening

Placenta accreta spectrum (PAS) is a severe complication of pregnancy associated with excessive invasion of cytotrophoblast cells at the sites of the endometrial-myometrial interface and the myometrium itself in cases of adherent (creta) and invasive (increta and percreta) forms, respectively. This leads to a high risk of massive blood loss, maternal hysterectomy, and preterm birth. Despite advancements in ultrasound protocols and found associations of alpha-fetoprotein, PAPP-A, hCG, PLGF, sFlt-1, IL-8, and IL-33 peripheral blood levels with PAS, there is a high need for an additional non-invasive test to improve the diagnostic accuracy and to select the real PAS from the suspected ones in the first-trimester screening. miRNA signatures of placental tissue, myometrium, and blood plasma from women with PAS in the third trimester of pregnancy, as well as miRNA profiles in exosomes from the blood serum of women in the first trimester with physiologically progressing pregnancy, complicated by PAS or pre-eclampsia, were obtained using deep sequencing. Two logistic regression models were constructed, both featuring statistically significant parameters related to the levels of miR-26a-5p, miR-17-5p, and miR-101-3p, quantified by real-time PCR in native blood serum. These models demonstrated 100% sensitivity in detecting PAS during the first pregnancy screening. These miRNAs were identified as specific markers for PAS, showing significant differences in their blood serum levels during the first trimester in the PAS group compared to those in physiological pregnancies, early- or late-onset pre-eclampsia groups. Furthermore, these miRNAs exhibited differential expression in the PAS placenta and/or myometrium in the third trimester and, according to data from the literature, control angiogenesis. Significant correlations were found between extracellular hsa-miR-101-3p and nuchal translucency thickness, hsa-miR-17-5p and uterine artery pulsatility index, and hsa-miR-26a-5p and hsa-miR-17-5p with PLGF. The developed test system for early non-invasive PAS diagnosis based on the blood serum level of extracellular miR-26a-5p, miR-17-5p, and miR-101-3p can serve as an auxiliary method for first-trimester screening of pregnant women, subject to validation with independent test samples.

Transabdominal and transvaginal ultrasound findings help to guide the clinical management of placenta accreta spectrum cases

INTRODUCTION

The clinical management of placenta accreta spectrum (PAS) depends on placental topography and vascular involvement. Our aim was to determine whether transabdominal and transvaginal ultrasound signs can predict PAS management.

MATERIAL AND METHODS

We conducted a retrospective cohort study of consecutive prenatally suspected PAS cases in a single tertiary-care PAS center between January 2021 and July 2022. When PAS was confirmed during surgery, abdominal and transvaginal ultrasound scans were analyzed in relation to PAS management. The preferred surgical approach of PAS was one-step conservative surgery (OSCS). Massive blood loss and PAS topography in the lower bladder trigone necessitated cesarean hysterectomy. Transvaginal ultrasound-diagnosed intracervical hypervascularity was split into three categories based on their quantity. Anatomically, the internal cervical os is located at the level of the bladder trigone and was used as landmark for upper and lower bladder trigone PAS.

RESULTS

Ninety-one women underwent OSCS and 35 women underwent cesarean hysterectomy (total 126 women with PAS). Abdominal and transvaginal ultrasound features differed significantly between women that underwent OSCS and cesarean hysterectomy: decreased myometrial thickness (<1 mm), 82.4% vs. 100%, p = 0.006; placental bulge, 51.6% vs. 94.3%, p < 0.001; bladder wall interruption, 62.6% vs. 97.1%, p < 0.001; abnormal placental lacunae, 75.8% vs. 100%, p < 0.001; hypervascularity (large lacunae feeding vessels, 57.8% vs. 94.6%, p < 0.001; parametrial hypervascularity, 15.4% vs. 60%, p < 0.001; the rail sign, 6.6% vs. 28.6%, p = 0.003; three-dimensional Doppler intra-placental hypervascularity, 81.3% vs. 100%, p < 0.001; intracervical hypervascularity 60.4% vs. 94.3%, p < 0.001); and cervical length 2.5 ± 0.94 vs. 2.2 ± 0.73, p = 0.038. Other ultrasound signs were not significantly different. The results of multivariable logistic regression showed placental bulge (odds ratio [OR] 9.3; 95% CI 1.9-44.3; p = 0.005), parametrial hypervascularity (OR 4.1; 95% CI 1.541-11.085; p = 0.005), and intracervical hypervascularity (OR 9.2; 95% CI 1.905-44.056; p = 0.006) were weak predictors of OSCS. Intracervical hypervascularity Grade 1 (vascularity <50% of cervical tissue) was more present in OSCS than higher gradings two and three (91% vs. 27.6% vs. 14.3%; p < 0.001).

CONCLUSIONS

Cesarean hysterectomy is associated with the PAS signs of placental bulge and Grade 2 and 3 intracervical hypervascularity. OSCS is associated with intracervical hypervascularity Grade 1 on transvaginal ultrasound. Prospective validation is required to formulate predictors for PAS management.

Clinical Outcomes of a False-Positive Antenatal Diagnosis of Placenta Accreta Spectrum

OBJECTIVE

 Antenatal diagnosis of placenta accreta spectrum (PAS) is critical to reduce maternal morbidity. While clinical outcomes of women with PAS have been extensively described, little information is available regarding the women who undergo cesarean delivery with a presumptive PAS diagnosis that is not confirmed by histopathologic examination. We sought to examine resource utilization and clinical outcomes of this group of women with a false-positive diagnosis of PAS.

STUDY DESIGN

 This is a retrospective analysis of patients with prenatally diagnosed PAS cared for between 2015 and 2020 by our multidisciplinary PAS team. Maternal outcomes were examined. Univariate analysis was performed and a multivariate model was employed to compare outcomes between women with and without histopathologically confirmed PAS.

RESULTS

 A total of 162 patients delivered with the preoperative diagnosis of PAS. Of these, 146 (90%) underwent hysterectomy and had histopathologic confirmation of PAS. Thirteen women did not undergo the planned hysterectomy. Three women underwent hysterectomy but pathologic examination did not confirm PAS. In comparing women with and without pathologic confirmation of PAS, the false-positive PAS group delivered later in pregnancy (34 vs. 33 weeks of gestation, p = 0.015) and had more planned surgery (88 vs. 47%, p = 0.002). There was no difference in skin incision type or hysterotomy placement for delivery. No significant difference in either the estimated blood loss or blood components transfused was noted between groups.

CONCLUSION

 Careful intraoperative evaluation of women with preoperatively presumed PAS resulted in a 3/149 (2%) retrospectively unnecessary hysterectomy. Management of women with PAS in experienced centers benefits patients in terms of both resource utilization and avoidance of unnecessary maternal morbidity, understanding that our results are produced in a center of excellence for PAS. We also propose a management protocol to assist in the avoidance of unnecessary hysterectomy in women with the preoperative diagnosis of PAS.

KEY POINTS

· Evaluation and delivery planning of patients with suspected placenta accreta spectrum in experienced centers provides acceptable outcomes.. · Under specific circumstances, delivery of placenta may be attempted if placenta accreta is suspected.. · Patients with suspected placenta accreta rarely undergo unindicated hysterectomy..

Termination of a second-trimester pregnancy with placenta accreta spectrum disorder

Background: The termination of pregnancy in patients with placenta accreta spectrum disorder (PASD) during the second trimester remains uncertain. In addition, interventional radiology techniques, such as arterial embolization and balloon placement, are potential options. We evaluated the outcomes of pregnancy termination in patients with PASD during the second trimester and the effectiveness of preoperative interventional radiology techniques.Methods: This retrospective study analyzed 48 PASD patients who underwent pregnancy termination during the second trimester between January 2016 and May 2021.Results: Of the 48 patients, 20 (41.67%) underwent transvaginal termination, whereas 28 (58.33%) underwent cesarean section. Notably, no significant differences were observed in success rates between the transvaginal termination and cesarean section groups (80.00% vs. 92.86%, P = 0.38). Furthermore, no statistically significant differences were observed in the success rates (94.12% vs 90.32%, P = 1.00) and blood loss (512.35 ± 727.00 ml vs 804.00 ± 838.98 ml, P = 0.23) between the artery embolization and non-embolization groups. In the vaginal termination group, statistically significant differences were observed in gestational weeks (16.70 ± 3.12 vs 22.67 ± 3.63, P < 0.01) and blood loss (165.00 ± 274.43 ml vs 483.64 ± 333.53 ml, P = 0.04) between the (artery embolization and non-embolization) subgroups. Conversely, in the cesarean section group, no significant differences were observed in gestational weeks (23.59 ± 3.14 vs 23.20 ± 4.37, P = 0.79) and blood loss (811.11 ± 879.55 ml vs 989.47 ± 986.52 ml, P = 0.76) between the subgroups.Conclusions: Further studies are needed to evaluate the efficacy of vaginal termination in PASD patients during the second trimester. Regarding cesarean termination, arterial embolization did not demonstrate increased effectiveness.

Prophylactic radiologic interventions to reduce postpartum hemorrhage in women with risk factors for placenta accreta spectrum disorder: a nationwide cohort study

OBJECTIVE

To quantify the association between prophylactic radiologic interventions and perioperative blood loss in women with risk factors for placenta accreta spectrum disorder (PAS).

METHODS

We conducted a retrospective nationwide cohort study of women with risk factors for placenta accreta spectrum disorder who underwent planned cesarean section in 69 Dutch hospitals between 2008 and 2013. All women had two risk factors for PAS: placenta previa/anterior low-lying placenta and a history of cesarean section(s). Women with and without ultrasonographic signs of PAS were studied as two separate groups. We compared the total blood loss of women with prophylactic radiologic interventions, defined as preoperative placement of balloon catheters or sheaths in the internal iliac or uterine arteries, with that of a control group consisting of women without prophylactic radiologic interventions using multivariable regression. We evaluated maternal morbidity by the number of red blood cell (RBC) units transfused within 24 h following childbirth (categories: 0, 1-3, >4), duration of hospital admission, and need for intensive care unit (ICU) admission.

RESULTS

A total of 350 women with placenta previa/anterior low-lying placenta and history of cesarean section(s) were included: 289 with normal ultrasonography, of whom 21 received prophylactic radiologic intervention, and 61 had abnormal ultrasonography, of whom 22 received prophylactic intervention. Among women with normal ultrasonography without prophylactic intervention (n = 268), the median blood loss was 725 mL (interquartile range (IQR) 500-1500) vs. 1000 mL (IQR 550-1750) in women with intervention (n = 21); the adjusted difference in blood loss was 9 mL (95% confidence interval (CI) -315-513), p = .97). Among women with abnormal ultrasonography, those without prophylactic intervention (n = 39) had a median blood loss of 2500 mL (IQR 1200-5000) vs. 1750 mL (IQR 775-4000) in women with intervention (n = 22); the adjusted difference in blood loss was -1141 mL (95% CI -1694- -219, p = .02). Results of outcomes on maternal morbidity were comparable among women with and without prophylactic intervention.

CONCLUSION

These findings suggest that prophylactic radiologic interventions prior to planned cesarean section may help to limit perioperative blood loss in women with clear signs of placenta accreta spectrum disorder on ultrasonography, but there was no evidence of a difference within the subgroup without such ultrasonographic signs. The use of these interventions should be discussed in a multidisciplinary shared decision-making process, including discussions of potential benefits and possible complications.

TRIAL REGISTRATION

Netherlands Trial Registry, https://onderzoekmetmensen.nl/en/trial/28238, identifier NL4210 (NTR4363).

Placental MRI segmentation based on multi-receptive field and mixed attention separation mechanism

OBJECTIVE

To reduce the occurrence of massive bleeding during placental abruption in patients with placenta accrete, we established a medical imaging based on multi-receptive field and mixed attention separation mechanism (MRF-MAS) model to improve the accuracy of MRI placenta segmentation and provide a basis for subsequent placenta accreta.

METHODS

We propose a placenta MRI segmentation technology using the MRF-MAS framework to develop a medical image diagnostic technique. The model first uses the multi-receptive field feature structure to obtain multi-level information, and improves the expression of features at differing scales. Note that the hybrid attention mechanism combines channel attention and spatial attention, separates the input feature sets and computes the attention separately, and finally reorganizes the feature maps. To show that the model can improve the accuracy of segmenting the placenta, we adopt mean Intersection over Union (IoU), Dice similarity coefficient (Dice) and area under the receiver operating characteristic curve (AUC) with U-Net, Mask RCNN, Deeplab v3 for comparison.

RESULTS

The four models achieved different outcomes based on our placenta dataset, with our model IoU and Dice up to 0.8169 and 0.8992, which are 5.51% and 3.03% higher than the average of the three comparison models.

CONCLUSION

The model proposed by us is helpful to assist the imaging diagnosis and at the same time provides a quantitative reference for the precise treatment of placenta accreta, assists the Equationtion of the clinical operation plan of the physician, and promotes the precision medicine of placenta accreta.

Placenta accreta spectrum in early and late pregnancy from an imaging perspective. A scoping review

Placenta accreta spectrum (PAS) disorders (with increasing order of the depth of invasion: accreta, increta, percreta) are quite challenging for the purpose of diagnosis and treatment. Pathological examination or imaging evaluation are not very dependable when considered as stand-alone diagnostic tools. On the other hand, timely diagnosis is of great importance, as maternal and fetal mortality drastically increases if patient goes through the third phase of delivery in a not well-suited facility. A multidisciplinary approach for diagnosis (incorporating clinical, imaging, and pathological evaluation) is mandatory, particularly in complicated cases. For imaging evaluation, the diagnostic modality of choice in most scenarios is ultrasound (US) exam; patients are referred for MRI when US is equivocal, inconclusive, or not visualizing placenta properly. Herewith, we review the reported US and MRI features of PAS disorders (mainly focusing on MRI), going over the normal placental imaging and imaging pitfalls in each section, and lastly, covering the imaging findings of PAS disorders in the first trimester and cesarean section pregnancy (CSP).

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

PURPOSE

To 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.

METHOD

Our 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.

RESULTS

A 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).

CONCLUSION

A 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.

Intraoperative Multivessel Embolization Reduces Blood Loss and Transfusion Requirements Compared to Internal Iliac Artery Balloon Placement during Cesarean Hysterectomy for Placenta Accreta Spectrum

PURPOSE

To evaluate the effectiveness and safety of prophylactic multivessel selective embolization (MVSE) compared to those of internal iliac artery occlusion balloon (IIABO) placement in patients undergoing cesarean hysterectomy for placenta accreta spectrum (PAS).

MATERIALS AND METHODS

An institutional review board-approved retrospective series was conducted with consecutive patients with PAS at a single institution between 2010 and 2021. MVSE was performed in a hybrid operating room after cesarean section prior to hysterectomy. IIABO was performed with balloons placed into the bilateral internal iliac arteries, which were inflated during hysterectomy. Median blood loss, transfusion requirements, percentage of cases requiring transfusion, and adverse events were recorded.

RESULTS

A total of 20 patients treated with embolization and 34 patients with balloon placement were included. Placenta percreta and previa were seen in 60% and 90% of patients, respectively. Median blood loss in the MVSE group was 713 mL (interquartile range [IQR], 475-1,000 mL) compared to 2,000 mL (IQR, 1,500-2,425 mL) in the IIABO group (P < .0001). The median total number of units of packed red blood cell transfusions (0 vs 2.5) and percentage of cases requiring a transfusion (20% vs 65%) were less in the MVSE group (P < .01). A median of 4 vessels (IQR, 3-9) were embolized during MVSE. No major adverse events or nontarget embolization consequences were observed.

CONCLUSIONS

Prophylactic MVSE is a safe procedure that reduces operative blood loss and transfusion requirements compared to those of IIABO in patients undergoing cesarean hysterectomy for presumed higher-degree PAS.

Effective training program for antenatal diagnosis of placenta accreta spectrum disorder

OBJECTIVE

To develop and evaluate a training program for diagnosing placenta accreta spectrum (PAS) disorder in obstetrics/gynecology and radiology residents.

METHODS

This single-center prospective study was based on 177 ultrasound images of pathologically confirmed PAS extracted from 534 cases of placenta previa suspicious for PAS. First- to third-year residents were evaluated before training to assess experience and ability to diagnose PAS. They attended a principal lecture followed by weekly self-study exercises over 5 weeks. Post-course tests evaluated the efficacy of the training program for improving diagnosis of PAS after the program.

RESULTS

Twenty-three (38.3%) obstetrics/gynecology and 37 (61.7%) radiology residents were trained. Before the training program, 98.3% reported minimal experience and 100% low confidence to correctly diagnose PAS. During the program, the overall accuracy of all participants in diagnosing PAS increased from 71.3% before to 95.2% after training (P < 0.001). Regression analyses showed that ability to diagnose PAS increased 2.52-fold (P < 0.001) following the program. The retention of knowledge at 1, 3, and 6 months posttest was 84.7%, 87.5%, and 87.7%, respectively.

CONCLUSION

An antenatal diagnosis of PAS training program can be effective as a residency training program, considering the globally rising cesarean delivery rates.

Use of super resolution reconstruction MRI for surgical planning in Placenta accreta spectrum disorder: Case series

INTRODUCTION

Comprehensive imaging using ultrasound and MRI of placenta accreta spectrum (PAS) aims to prevent catastrophic haemorrhage and maternal death. Standard MRI of the placenta is limited by between-slice motion which can be mitigated by super-resolution reconstruction (SRR) MRI. We applied SRR in suspected PAS cases to determine its ability to enhance anatomical placental assessment and predict adverse maternal outcome.

METHODS

Suspected PAS patients (n = 22) underwent MRI at a gestational age (weeks + days) of (32+3±3+2, range (27+1-38+6)). SRR of the placental-myometrial-bladder interface involving rigid motion correction of acquired MRI slices combined with robust outlier detection to reconstruct an isotropic high-resolution volume, was achieved in twelve. 2D MRI or SRR images alone, and paired data were assessed by four radiologists in three review rounds. All radiologists were blinded to results of the ultrasound, original MR image reports, case outcomes, and PAS diagnosis. A Random Forest Classification model was used to highlight the most predictive pathological MRI markers for major obstetric haemorrhage (MOH), bladder adherence (BA), and placental attachment depth (PAD).

RESULTS

At delivery, four patients had placenta praevia with no abnormal attachment, two were clinically diagnosed with PAS, and six had histopathological PAS confirmation. Pathological MRI markers (T2-dark intraplacental bands, and loss of retroplacental T2-hypointense line) predicting MOH were more visible using SRR imaging (accuracy 0.73), in comparison to 2D MRI or paired imaging. Bladder wall interruption, predicting BA, was only easily detected by paired imaging (accuracy 0.72). Better detection of certain pathological markers predicting PAD was found using 2D MRI (placental bulge and myometrial thinning (accuracy 0.81)), and SRR (loss of retroplacental T2-hypointense line (accuracy 0.82)).

DISCUSSION

The addition of SRR to 2D MRI potentially improved anatomical assessment of certain pathological MRI markers of abnormal placentation that predict maternal morbidity which may benefit surgical planning.

Radiomics-based prediction of FIGO grade for placenta accreta spectrum

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

RELEVANCE STATEMENT

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

KEY POINTS

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

[Prenatal diagnosis of placenta acretta by ultrasound and its histopathological association]

Background

Anomalous adhesions of the placenta, known as placenta accreta and its variants, are the cause of obstetric hemorrhages that put the pregnant woman at risk. Accretism is strongly associated with a history of uterine surgery (cesarean section, myomectomy, curettage), as well as ultrasonographic signs, such as the presence and size of placental lacunae, loss of the placenta/bladder interface, location on the anterior face of the placenta, and presence of Doppler flow; these markers can be assessed by prenatal ultrasound.

Objective

To analyze the association of prenatal diagnosis of placenta accreta by ultrasound with the histopathological result using the Tovbin index.

Material and methods

Observational, cross-sectional and analytical study. 63 patients who had placenta accreta data by ultrasound measured with the Tovbin index and by means of the histopathological result obtained from the platform of the Mexican Institute for Social Security (IMSS) were included. The association between the two studies with the presence of placenta accreta was analyzed.

Results

63 patients were analyzed; the Tovbin index was positive in 89% of the patients with a diagnosis of placenta accreta confirmed by histopathology. Both the Tovbin index and the histopathology report showed a statistically significant association with a p value of 0.04 for the diagnosis of placenta accreta.

Conclusion

The Tovbin index as an ultrasonographic prenatal diagnosis of placenta accreta has a statistically significant association with histopathology diagnosis.

Association of MRI Features and Adverse Maternal Outcome in Patients With Placenta Accreta Spectrum Disorders After Abdominal Aortic Balloon Occlusion

BACKGROUND

MRI features may be associated with adverse maternal outcome in patients with placenta accreta spectrum (PAS) disorders even with abdominal aortic balloon occlusion (AABO).

PURPOSE

This study aimed to identify risk factors of MRI for association with adverse maternal outcome in patients with PAS disorders after AABO.

STUDY TYPE

Retrospective.

POPULATION

Clinical and MRI features of 80 patients were retrospectively reviewed from October 2016 to August 2021. A total of 40 patients had adverse maternal outcomes including intrapartum/peripartum bleeding >1000 mL and/or emergency hysterectomy after AABO.

SEQUENCE

Half-Fourier acquisition single-shot turbo spin echo and gradient echo imaging True fast imaging with steady-state precession (True-FISP) at 1.5T MR scanner.

ASSESSMENT

MRI features were evaluated by three radiologists and were tested for any association with adverse maternal outcome.

STATISTICAL TESTS

Interobserver agreement was calculated with kappa (k) statistics. Association between MRI features and adverse maternal outcomes were evaluated by univariate and multivariate analyses. A nomogram was constructed based on the logistic regression.

RESULTS

The interobserver agreement ranged from fair to substantial (k = 0.379-0.783). Multivariate analyses revealed that short cervical length (OR: 4.344), abnormal intraplacental vascularity (OR: 6.005), placental bulge (OR: 9.085), and myometrial interruption (OR: 9.550) were independent risk factors for adverse maternal outcomes. The combination of four risk factors together demonstrated the highest AUC of 0.851 (95% CI 0.769-0.933) with a sensitivity and specificity of 77.5% and 72.5%, respectively and then a nomogram composed of the above four risk factors was constructed to represent the probability of adverse maternal outcome.

DATA CONCLUSION

The nomogram demonstrated the association between MRI features and patient's poor outcome after undergoing AABO and C-section delivery for PAS.

EVIDENCE LEVEL

4 TECHNICAL EFFICACY: Stage 3.

External Validation of a Multivariable Prediction Model for Placenta Accreta Spectrum

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Treatment of infected placenta accreta in the uterine horn by transabdominal temporary occlusion of internal iliac arteries: A case report and literature review

RATIONALE

This case report aims to describe the treatment of infected placenta accreta in the uterine horn by transabdominal temporary occlusion of internal iliac arteries.

PATIENT CONCERNS

A 29-year-old female patient had a history of retained placenta for 28 days after labor induction in the second trimester of pregnancy because of fetal malformation.

DIAGNOSES

Placenta accreta in the uterine horn was diagnosed by 3-dimensional ultrasound and magnetic resonance imaging, and the diagnosis was confirmed during the operation.

INTERVENTIONS

Laparotomy was performed to remove the placenta and repair the uterine defect after temporary occlusion of both internal iliac arteries.

OUTCOMES

Body temperature and inflammatory markers were elevated at admission but returned to normal on the second day after surgery. Normal menstruation resumed approximately 1 month postoperatively. Ultrasound examination showed that the shape of the uterine cavity was normal. No postoperative complications were observed.

LESSONS

Temporary occlusion of the internal iliac artery can help effectively manage infected placenta accreta in the uterine horn.

Ultrasound scoring system for prenatal diagnosis of placenta accreta spectrum

BACKGROUND

To develop an ultrasound scoring system for placenta accreta spectrum (PAS), evaluate its diagnostic value, and provide a practical approach to prenatal diagnosis of PAS.

METHODS

A total of 532 pregnant women (n = 184 no PAS, n = 120 placenta accreta, n = 189 placenta increta, n = 39 placenta percreta) at high-risk for placenta accreta who delivered in the Third Affiliated Hospital of Zhengzhou University between January 2021 and December 2022 underwent prenatal ultrasound to evaluate placental invasion. An ultrasound scoring system that included placental and cervical morphology and history of cesarean section was created. Each feature was assigned a score of 0 ~ 2, according to severity. Thresholds for the total ultrasound score that discriminated between no PAS, placenta accreta, placenta increta, and placenta percreta were calculated.

RESULTS

Univariate and multivariate regression analysis identified seven indicators of PAS that were included in the ultrasound scoring system, including placental location, placental thickness, presence/absence of the retroplacental space, thickness of the retroplacental myometrium, presence/absence of placental lacunae, retroplacental myometrial blood flow and history of cesarean section. Using the final ultrasound scoring system, no PAS is diagnosed at a total score < 5, placenta accreta or placenta increta is diagnosed at a total score 5-10, and placenta percreta is diagnosed at a total score ≥ 10.

CONCLUSIONS

This study identified seven indicators of PAS and included them in an ultrasound scoring system that has good diagnostic efficacy and clinical utility.

TRIAL REGISTRATION

ChiCTR2300069261 (retrospectively registered on 10/03/2023).

Routine screening for placenta accreta spectrum

Screening for clinically significant placenta accreta spectrum (PAS) is possible with a high degree of accuracy (both sensitivity and specificity >90-95%). The group of women to focus on are those with placenta previa and one or more prior Cesarean deliveries. Screening for PAS not associated with placenta previa is not as productive, and several false negatives have been described. The results of the screening program indicate that women have a low or high probability of PAS. Screen-positive women or those with uncertain ultrasound features should be referred to a center of excellence. Those confirmed to have a high probability of PAS should electively be delivered at such centers.

Prediction of placenta accreta spectrum with nomogram combining radiomic and clinical factors: A novel developed and validated integrative model

OBJECTIVE

To develop and validate a clinicoradiomic nomogram based on sagittal T2WI images to predict placenta accreta spectrum (PAS).

METHODS

Between October 2016 and April 2022, women suspected of PAS by ultrasound were enrolled. After taking into account exclusion criteria, 132 women were retrospectively included in the study. The variance threshold SelectKBest and the least absolute shrinkage and selection operator were applied to select radiomic features, which was further used to calculate the Rad-score. Multivariable logistic regression was used to screen clinical factor.

RESULTS

Based on 13 radiomic features, five radiomic models were constructed. A clinical factor of intraplacental T2-hypointense bands was obtained by multivariate logistic regression. The area under the curve (AUC) value of the stochastic gradient descent (SGD) radiomic model was 0.82 in the training cohort and 0.78 in the test cohort. After adding clinical factors to the SGD radiomic model, the AUC value of the clinicoradiomic model was significantly increased from 0.82 and 0.78 to 0.84 in both the training and test cohorts. The nomogram of the clinicoradiomic model was constructed, which had good performance verified by calibration and a decision curve.

CONCLUSION

The presented nomogram could be useful for predicting PAS.

Validation of a sonographic checklist for the detection of histologic placenta accreta spectrum

BACKGROUND

To standardize research terminology and to reduce unanticipated placenta accreta spectrum, the European Working Group for Abnormally Invasive Placenta developed a consensus checklist for reporting suspected placenta accreta spectrum observed during an antenatal ultrasound. The diagnostic accuracy of the European Working Group for Abnormally Invasive Placenta checklist has not been assessed.

OBJECTIVE

This study aimed to test the performance of the European Working Group for Abnormally Invasive Placenta sonographic checklist in predicting histologic placenta accreta spectrum.

STUDY DESIGN

This was a multisite, blinded, retrospective review of transabdominal ultrasound studies performed between 26 to 32 weeks' gestation for subjects with histologic placenta accreta spectrum between 2016 and 2020. We matched a control cohort of subjects without histologic placenta accreta spectrum in a 1:1 ratio. To reduce reader bias, we matched the control cohort for known risk factors including previa, number of previous cesarean deliveries, previous dilation and curettage, in vitro fertilization, and clinical factors affecting image quality including multiple gestation, body mass index, and gestational age at the ultrasound. Nine sonologists from 5 referral centers, blinded to the histologic outcomes, interpreted the randomized ultrasound studies using the European Working Group for Abnormally Invasive Placenta checklist. The primary outcome was the sensitivity and specificity of the checklist to predict placenta accreta spectrum. Two separate sensitivity analyses were performed. First, we excluded subjects with mild disease (ie, only assessed subjects with histologic increta and percreta). Second, we excluded interpretations from the 2 most junior sonologists.

RESULTS

A total of 78 subjects were included (39 placenta accreta spectrum, 39 matched control). Clinical risk factors and image quality markers were statistically similar between the cohorts. The checklist sensitivity (95% confidence interval) was 76.6% (63.4-90.6) and the specificity (95% confidence interval) was 92.0% (63.4-99.9) with a positive and negative likelihood ratio of 9.6 and 0.3, respectively. When we excluded subjects with mild placenta accreta spectrum disease, the sensitivity (95% confidence interval) increased to 84.7% (73.6-96.4) and the specificity was unchanged at 92.0% (83.2-99.9). Sensitivity and specificity were unchanged when the interpretations from the 2 most junior sonologists were excluded.

CONCLUSION

The 2016 European Working Group for Abnormally Invasive Placenta checklist for interpreting placenta accreta spectrum has a reasonable performance in detecting histologic placenta accreta spectrum and excluding cases without placenta accreta spectum.

Placenta Accreta Spectrum

Placenta accreta spectrum (PAS) is one of the most dangerous conditions in pregnancy and is increasing in frequency. The risk of life-threatening bleeding is present throughout pregnancy but is particularly high at the time of delivery. Although the exact cause is unknown, the result is clear: Severe PAS distorts the uterus and surrounding anatomy and transforms the pelvis into an extremely high-flow vascular state. Screening for risk factors and assessing placental location by antenatal ultrasonography are essential for timely diagnosis. Further evaluation and confirmation of PAS are best performed in referral centers with expertise in antenatal imaging and surgical management of PAS. In the United States, cesarean hysterectomy with the placenta left in situ after delivery of the fetus is the most common treatment for PAS, but even in experienced referral centers, this treatment is often morbid, resulting in prolonged surgery, intraoperative injury to the urinary tract, blood transfusion, and admission to the intensive care unit. Postsurgical complications include high rates of posttraumatic stress disorder, pelvic pain, decreased quality of life, and depression. Team-based, patient-centered, evidence-based care from diagnosis to full recovery is needed to optimally manage this potentially deadly disorder. In a field that has relied mainly on expert opinion, more research is needed to explore alternative treatments and adjunctive surgical approaches to reduce blood loss and postoperative complications.

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.