Evaluation of classic and novel ultrasound signs of placenta accreta spectrum

Diagnostic accuracy of a specialized pro forma in assessing morbidly adherent placenta in correlation to intra-operative findings

OBJECTIVES

To assess the clinical value of ultrasound criteria for the "Morbidly Adherent Placenta" (MAP) and the diagnostic accuracy of a customized "pro forma" in predicting MAP, its extent, and its relationship to intra-operative results.

METHODS

Twenty-one pregnant women with a high possibility of placenta accreta were included in the study. Gray scale transabdominal and transvaginal ultrasound with color Doppler were done to confirm the MAP diagnosis and evaluate the signs of placental invasion. The ultrasound findings were compared with the operative details to predict placental invasion (focal or diffuse) and vascularity of the lower uterine segment to assess the clinical significance of the customized "pro forma."

RESULTS

There was a good accuracy of ultrasound signs to detect the vascularity of the lower uterine segment with a sensitivity of 94.12%, specificity of 25%, positive predictive value (PPV) of 84.21%, negative predictive value (NPV) of 50%, and accuracy of 80.95%; however, it was insignificant (p = 0.352). Additionally, we found a good accuracy of ultrasound signs to detect the degree of placental invasion (focal or diffuse), with a sensitivity of 71.43%, specificity of 100%, PPV of 100%, NPV of 63.64%, and accuracy of 80.95%, which was significant (p = 0.004).

CONCLUSION

This customized "pro forma" has satisfactory accuracy in predicting MAP cases with anterior placenta previa or anterior low-lying placenta.

Intrahepatic cholestasis of pregnancy and coagulation: a dual risk of hypercoagulability and bleeding

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) is a hepatobiliary disorder characterized by elevated bile acid levels and liver dysfunction and usually occurs in the third trimester. Although the ICP has been associated with various fetal complications, its effects on maternal coagulation are poorly understood. Recent studies suggest that ICP may both cause hypercoagulability and increase bleeding tendency by impairing the synthesis of clotting factors. The aim of this study was to evaluate the relationships between ICP and coagulation parameters and to examine their potential clinical implications.

METHODS

This retrospective case‒control study included 175 pregnant women with ICP and 162 healthy women matched for gestational age. Demographic, biochemical and hematologic parameters were analyzed. The prothrombin time (PT), activated partial thromboplastin time (aPTT), international normalized ratio (INR) and fibrinogen levels were evaluated.

RESULTS

Fibrinogen levels were significantly greater in the ICP group (p < 0.01), but PT, aPTT and INR values were not significantly different (p > 0.05). In the postpartum period, 2 cases of venous thromboembolism (VTE) were observed in the ICP group, whereas no cases of VTE were observed in the control group. Furthermore, the mean gestational age at delivery was significantly lower in ICP patients (253.75 ± 15.53 days vs. 271.43 ± 10.26 days, p < 0.01). Fetal complication rates were also significantly higher; the most common complications were fetal distress (7.4%), meconium aspiration (6.3%), preterm labor (4.0%) and fetal growth restriction (FGR) (2.9%).

CONCLUSION

In ICP patients, hypercoagulability is a clinically significant concern that should be considered alongside bleeding risk. In our study, no significant differences were observed in routine coagulation tests, suggesting that more sensitive coagulation markers should be evaluated in ICP patients. The high rate of fetal complications indicates that early diagnosis, careful monitoring, and the implementation of individualized management plans are essential for the prevention of hematological and perinatal complications in pregnant women with intrahepatic cholestasis.

Advances in Prenatal Diagnosis of Placenta Accreta Spectrum

Placenta accreta spectrum (PAS) involves abnormal placental attachment and can lead to severe complications such as postpartum hemorrhage and hysterectomy. Ultrasound is the main tool used to screen for PAS due to its non-invasive nature and convenience, although its accuracy depends on the skill of the operator. Magnetic Resonance Imaging has emerged as a supplementary tool, especially for complex cases or posterior placentas, providing more accurate anatomical detail and enabling the invasion depth and location to be assessed. This review summarizes recent advances in prenatal imaging for PAS, aiming to improve diagnostic accuracy and guide future research.

Diffusion lacunae: a novel MR imaging finding on diffusion-weighted imaging for diagnosing placenta accreta spectrum

OBJECTIVE

To evaluate the usefulness of novel diffusion-weighted imaging (DWI) findings for diagnosing placenta accreta spectrum (PAS).

MATERIALS AND METHODS

This retrospective study included 49 pregnant women with suspected PAS who underwent 1.5 T placental MRI. Diffusion lacunae were defined as intraplacental areas showing hypointensity on DWI and hyperintensity on the apparent diffusion coefficient map. Two radiologists evaluated the number and size of placental lacunae on DWI, and flow void in the diffusion lacunae on T2-weighted imaging. The radiologists also evaluated established MRI features of PAS described in the SAR-ESUR consensus statement. Pearson's chi-square test or Mann-Whitney U test was used to compare findings between patients with and without PAS. Interobserver reliability for DWI and established MRI features was also assessed. Optimal thresholds for the number and maximum size of diffusion lacunae for differentiating PAS from the no-PAS group were determined using receiver operating characteristic curve analyses.

RESULTS

Eighteen patients were diagnosed with PAS, and 31 patients with placental previa without PAS. The number and maximum size of diffusion lacunae were significantly larger in patients with than in patients without PAS (p < 0.0001). Combining assessment of the number of diffusion lacunae with assessment of their maximum size yielded a diagnostic performance with sensitivity, specificity and accuracy of 83%, 94% and 90%, respectively. Flow voids within the diffusion lacunae had sensitivity, specificity and accuracy of 88%, 84% and 86%, respectively.

CONCLUSION

The number and size of diffusion lacunae, and T2 flow void in diffusion lacunae may be useful findings for diagnosing PAS.

Prenatal identification of invasive placentation using ultrasound in women with placenta previa and prior cesarean delivery

OBJECTIVE

To evaluate the performance of ultrasound for antenatal identification of invasive placentation in women with placenta previa in the setting of prior cesarean delivery.

STUDY DESIGN

This was a multicenter, retrospective, cohort study. Singleton pregnancies at risk of placenta accreta because of persistent placenta previa in the setting of prior cesarean delivery who delivered at four centers, from January 2010 to May 2020, were included in the study. For this study, pregnancies with diagnosis of accreta, increta, or percreta were considered under the umbrella term of placenta accreta. All women with placenta previa identified in the second trimester had a follow-up ultrasound at 32-34 weeks. Only those with prior cesarean delivery were considered at risk of placenta accreta. Women were considered with suspected accreta in case of suspected prenatal ultrasound. Women with suspected placenta accreta had delivery planned via cesarean hysterectomy at 34+0 - 35+6 weeks, without any attempt to remove the placenta. The primary endpoint of the study was the performance of ultrasound for antenatal identification of invasive placentation. The following ultrasound signs were evaluated: placenta lacunae; loss of clear space; increased vascularity between myometrium and placenta; intracervical lake; rail sign; uterovesical hypervascularity; increased vascularity in the inferior part of the lower uterine segment potentially extending into the parametrial region; and disruption of bladder-myometrial interface.

RESULTS

180 singleton pregnancies with placenta previa in the setting of prior cesarean delivery were identified. Of them, 155 (86.1%) had antenatal suspected placenta accreta based on ultrasound, having at least one sign of invasive placentation. Of the 155 suspected cases, 99 had confirmed placenta accreta at the time of delivery. Among the 99 cases of confirmed placenta accreta, all of them had at least one sign of invasive placentation at ultrasound. Among the 81 cases with placenta previa, prior cesarean delivery, without placenta accreta, 25/81 (30.9%) had ultrasound scan negative for sign of invasive placentation, and 56/81 (69.1%) had at least one sign of invasive placentation). In particular, 12/81 (14.8%) had placenta lacunae, 16/81 (19.8%) had loss of clear space, 20/81 (24.7%) had increased vascularity between myometrium and placenta, 9/81 (11.1%) had intracervical lake, 14/81 (17.3%) had rail sign, 14 (17.3%) had uterovesical hypervascularity, 5/81 (6.2%) had increased vascularity in the inferior part of the lower uterine segment potentially extending into the parametrial region, 8/81 (9.9%) had disruption of bladder-myometrial interface. In the group of women with confirmed placenta accreta, the most common sign recorded was the disruption of bladder-myometrial interface, being recorded in 88/99 women. Disruption of bladder-myometrial interface had the highest sensitivity in detection placenta accreta. Women with disruption of bladder-myometrial interface at ultrasound had 73-fold increase in the risk of placenta accreta compared to those who did not.

CONCLUSION

Prenatal ultrasound has an excellent diagnostic accuracy in identifying invasive placentation in women with placenta previa and prior cesarean delivery.

Trimester-specific diagnostic accuracy of ultrasound for detection of placenta accreta spectrum: systematic review and meta-analysis

OBJECTIVE

To assess the diagnostic accuracy of ultrasound for detecting placenta accreta spectrum (PAS) during the first trimester of pregnancy and compare it with the accuracy of second- and third-trimester ultrasound examination in pregnancies at risk for PAS.

METHODS

PubMed, EMBASE and Web of Science databases were searched to identify relevant studies published from inception until 10 March 2023. Inclusion criteria were cohort, case-control or cross-sectional studies that evaluated the accuracy of ultrasound examination performed at < 14 weeks of gestation (first trimester) or ≥ 14 weeks of gestation (second/third trimester) for the diagnosis of PAS in pregnancies with clinical risk factors. The primary outcome was the diagnostic accuracy of sonography in detecting PAS in the first trimester, compared with the accuracy of ultrasound examination in the second and third trimesters. The secondary outcome was the diagnostic accuracy of each sonographic marker individually across the trimesters of pregnancy. The reference standard was PAS confirmed at pathological or surgical examination. The potential of ultrasound and different ultrasound signs to detect PAS was assessed by computing summary estimates of sensitivity, specificity, diagnostic odds ratio and positive and negative likelihood ratios.

RESULTS

A total of 37 studies, including 5764 pregnancies at risk of PAS, with 1348 cases of confirmed PAS, were included in our analysis. The meta-analysis demonstrated that ultrasound had a sensitivity of 86% (95% CI, 78-92%) and specificity of 63% (95% CI, 55-70%) during the first trimester, and a sensitivity of 88% (95% CI, 84-91%) and specificity of 92% (95% CI, 85-96%) during the second/third trimester. Regarding sonographic markers examined in the first trimester, lower uterine hypervascularity exhibited the highest sensitivity (97% (95% CI, 19-100%)), and uterovesical interface irregularity demonstrated the highest specificity (99% (95% CI, 96-100%)). In the second/third trimester, loss of clear zone had the highest sensitivity (80% (95% CI, 72-86%)), and uterovesical interface irregularity exhibited the highest specificity (99% (95% CI, 97-100%)).

CONCLUSIONS

First-trimester ultrasound examination has similar accuracy to second- and third-trimester ultrasound examinations for the diagnosis of PAS. Routine first-trimester ultrasound screening for patients at high risk of PAS may improve detection rates and allow earlier referral to tertiary care centers for pregnancy management. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

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).

Modified Delphi study of ultrasound signs associated with placenta accreta spectrum

OBJECTIVE

To determine, by expert consensus through a modified Delphi process, the role of standardized and new ultrasound signs in the prenatal evaluation of patients at high risk of placenta accreta spectrum (PAS).

METHODS

A systematic review of articles providing information on ultrasound imaging signs or markers associated with PAS was performed before the development of questionnaires for the first round of the Delphi process. Only peer-reviewed original research studies in the English language describing one or more new ultrasound sign(s) for the prenatal evaluation of PAS were included. A three-round consensus-building Delphi method was then conducted under the guidance of a steering group, which included nine experts who invited an international panel of experts in obstetric ultrasound imaging in the evaluation of patients at high risk for PAS. Consensus was defined as agreement of ≥ 70% between participants.

RESULTS

The systematic review identified 15 articles describing eight new ultrasound signs for the prenatal evaluation of PAS. A total of 35 external experts were approached, of whom 31 agreed and participated in the first round. Thirty external experts (97%) and seven experts from the steering group completed all three Delphi rounds. A consensus was reached that a prior history of at least one Cesarean delivery, myomectomy or PAS should be an indication for detailed PAS ultrasound assessment. The panelists also reached a consensus that seven of the 11 conventional signs of PAS should be included in the examination of high-risk patients and the routine mid-gestation scan report: (1) loss of the 'clear zone', (2) myometrial thinning, (3) bladder-wall interruption, (4) placental bulge, (5) uterovesical hypervascularity, (6) placental lacunae and (7) bridging vessels. A consensus was not reached for any of the eight new signs identified by the systematic review. With respect to other ultrasound features that are not specific to PAS but increase the probability of PAS at birth, the panelists reached a consensus for the finding of anterior placenta previa or placenta previa with cervical involvement. The experts were also asked to determine which PAS signs should be quantified and consensus was reached only for the quantification of placental lacunae using an existing score. For predicting surgical outcome in patients with a high probability of PAS at delivery, a consensus was obtained for loss of the clear zone, bladder-wall interruption, presence of placental lacunae and presence of placenta previa involving the cervix.

CONCLUSIONS

We have confirmed the continued importance of seven established standardized ultrasound signs of PAS, highlighted the role of transvaginal ultrasound in evaluating the placental position and anatomy of the cervix, and identified new ultrasound signs that may become useful in the future prenatal evaluation and management of patients at high risk for PAS at birth. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Separation sign: novel ultrasound sign for ruling out diagnosis of placenta accreta spectrum

OBJECTIVE

To assess the performance of the 'separation sign' as a predictor of normal placental separation in a large cohort of women at risk for placenta accreta spectrum (PAS) and in a high-risk subgroup with placenta previa or anterior low-lying placenta and at least one previous Cesarean delivery.

METHODS

This was a prospective study of women at risk for PAS referred to a specialist clinic at between 22 and 38 weeks' gestation. All women underwent ultrasound assessment for the presence of the separation sign, which detects the difference in elasticity between the myometrium and the placenta, characterized by different rates of rebound after an ultrasound probe is used to apply pressure over the uteroplacental interface. When the sign is positive, the placenta appears to move relative to the myometrium, leading to the appearance or enhancement of the clear zone. The predictive performance of the separation sign for normal spontaneous placental separation at delivery was assessed.

RESULTS

Of the 194 included women, 163 had a positive separation sign, all of whom went on to have normal placental separation at delivery. Of the 24 women with a negative separation sign, three (12.5%) had normal placental separation and 21 (87.5%) were diagnosed with PAS. This yielded a sensitivity of 98.2% (95% CI, 94.8-99.6%) and specificity of 100% (95% CI, 83.9-100%). In the high-risk cohort (n = 35), a positive separation sign remained a reliable predictor of normal placental separation, with a positive predictive value of 100%, sensitivity of 88.9% (95% CI, 65.3-98.6%) and specificity of 100% (95% CI, 80.5-100%).

CONCLUSIONS

The separation sign could be a useful tool in women considered to be at risk for PAS, as it can facilitate the prediction of normal placental separation at delivery. This may prevent overtreatment, the associated iatrogenic morbidity and unnecessary allocation of clinical resources. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Performance and Robustness of Regional Image Segmentation Driven by Selected Evolutionary and Genetic Algorithms: Study on MR Articular Cartilage Images

The analysis and segmentation of articular cartilage magnetic resonance (MR) images belongs to one of the most commonly routine tasks in diagnostics of the musculoskeletal system of the knee area. Conventional regional segmentation methods, which are based either on the histogram partitioning (e.g., Otsu method) or clustering methods (e.g., K-means), have been frequently used for the task of regional segmentation. Such methods are well known as fast and well working in the environment, where cartilage image features are reliably recognizable. The well-known fact is that the performance of these methods is prone to the image noise and artefacts. In this context, regional segmentation strategies, driven by either genetic algorithms or selected evolutionary computing strategies, have the potential to overcome these traditional methods such as Otsu thresholding or K-means in the context of their performance. These optimization strategies consecutively generate a pyramid of a possible set of histogram thresholds, of which the quality is evaluated by using the fitness function based on Kapur's entropy maximization to find the most optimal combination of thresholds for articular cartilage segmentation. On the other hand, such optimization strategies are often computationally demanding, which is a limitation of using such methods for a stack of MR images. In this study, we publish a comprehensive analysis of the optimization methods based on fuzzy soft segmentation, driven by artificial bee colony (ABC), particle swarm optimization (PSO), Darwinian particle swarm optimization (DPSO), and a genetic algorithm for an optimal thresholding selection against the routine segmentations Otsu and K-means for analysis and the features extraction of articular cartilage from MR images. This study objectively analyzes the performance of the segmentation strategies upon variable noise with dynamic intensities to report a segmentation's robustness in various image conditions for a various number of segmentation classes (4, 7, and 10), cartilage features (area, perimeter, and skeleton) extraction preciseness against the routine segmentation strategies, and lastly the computing time, which represents an important factor of segmentation performance. We use the same settings on individual optimization strategies: 100 iterations and 50 population. This study suggests that the combination of fuzzy thresholding with an ABC algorithm gives the best performance in the comparison with other methods as from the view of the segmentation influence of additive dynamic noise influence, also for cartilage features extraction. On the other hand, using genetic algorithms for cartilage segmentation in some cases does not give a good performance. In most cases, the analyzed optimization strategies significantly overcome the routine segmentation methods except for the computing time, which is normally lower for the routine algorithms. We also publish statistical tests of significance, showing differences in the performance of individual optimization strategies against Otsu and K-means method. Lastly, as a part of this study, we publish a software environment, integrating all the methods from this study.

Doppler evaluation of normal and abnormal placenta

Doppler techniques are needed for the evaluation of the intraplacental circulation and can be of great value in the diagnosis of placental anomalies. Highly sensitive Doppler techniques can differentiate between the maternal (spiral arteries) and fetal (intraplacental branches of the umbilical artery) components of the placental circulation and assist in the evaluation of the placental functional units. A reduced number of placental functional units can be associated with obstetric complications, such as fetal growth restriction. Doppler techniques can also provide information on decidual vessels and blood movement. Abnormal decidual circulation increases the risk of placenta accreta. Doppler evaluation of the placenta greatly contributes to the diagnosis and clinical management of placenta accreta, vasa previa, placental infarcts, placental infarction hematoma, maternal floor infarction, massive perivillous fibrin deposition and placental tumors. However, it has a limited role in the diagnosis and clinical management of placental abruption, placental hematomas, placental mesenchymal dysplasia and mapping of placental anastomoses in monochorionic twin pregnancies. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.