The relationship between cervical length and area measurements evaluated by MRI and the amount of hemorrhage in PAS cases.

BACKGROUND: Placenta accreta spectrum often leads to massive hemorrhage and even maternal shock and death. This study aims to identify whether cervical length and cervical area measured by magnetic resonance imaging correlate with massive hemorrhage in patients with placenta accreta spectrum. METHODS: The study was conducted at our hospital, and 158 placenta previa patients with placenta accreta spectrum underwent preoperative magnetic resonance imaging examination were included. The cervical length and cervical area were measured and evaluated their ability to identify massive hemorrhage in patients with placenta accreta spectrum. RESULTS: The cervical length and area in patients with massive hemorrhage were both significantly smaller than those in patients without massive hemorrhage. The results of multivariate analysis show that cervical length and cervical area were significantly associated with massive hemorrhage. In all patients, a negative linear was found between cervical length and amount of blood loss (r =-0.613), and between cervical area and amount of blood loss (r =-0.629). Combined with cervical length and cervical area, the sensitivity, specificity, and the area under the curve for the predictive massive hemorrhage were 88.618%, 90.209%, and 0.890, respectively. CONCLUSION: The cervical length and area might be used to recognize massive hemorrhage in placenta previa patients with placenta accreta spectrum.

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.

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.

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.

Cervical angle as a possible predictor of abnormal placental position in women with endometriosis.

BACKGROUND: We aimed to examine the effects of endometriosis on the rate of abnormal placentation by comparing the data of pregnant women with and without endometriosis. METHODS: A case-control study was conducted to compare the perinatal outcomes between women with and without endometriosis. In the subgroup analysis, magnetic resonance imaging (MRI) scans of pregnant women with placenta previa were used to measure the cervical angle and its relationship with endometriosis. The cervical angle was measured as the angle between the cervical glands and the line perpendicular to the spinal column in each sagittal MRI section. RESULTS: We retrospectively analyzed data from 3453 cases of singleton deliveries between 2015 and 2019 at two study facilities. Among them, 159 had clinically or surgically confirmed endometriosis. The odds ratio (OR) for abnormal placental position was significantly higher in pregnant women with endometriosis (OR. 2.82; 95% confidence interval [CI], 1.58-5.04). The OR was 3.21 (95% CI, 1.57-6.55) in the endometriosis-surgery group (91 patients) and 2.32 (95% CI, 0.91-5.88) in the non-surgery group (68 patients). Furthermore, 44 women who underwent pelvic MRI after 30 weeks of gestation were included to examine the cervical angle. Then, we compared the date of pregnant women with (n = 6) and without endometriosis (n = 38). Regardless of placental attachment position, the cervical angle was significantly lower in the group with than in the group without a history of endometriosis. CONCLUSION: Pregnant women with a history of endometriosis may have stronger uterine retroversion, which could potentially contribute to abnormal placental positioning.

Sonographic Predictors of Antepartum Bleeding in Placenta Previa.

OBJECTIVE: To evaluate the association between sonographic features of placenta previa and vaginal bleeding (VB). STUDY DESIGN: Retrospective cohort study of women with placenta previa identified on ultrasound between 160/7 and 276/7 weeks gestation. Placental distance past the cervical os (DPO), placental thickness, edge angle, and cervical length (CL) were measured. The primary outcome was any VB and the secondary outcome was VB requiring delivery. Median values of the sonographic features were compared for each of the outcomes using the Mann-Whitney U test. Receiver operating characteristic curves were used to compare the predictive value of sonographic variables markers and to determine optimal cut points for each measurement. Logistic regression was used to estimate the association between each measure and the outcomes while controlling for confounders. RESULTS: Of 149 women with placenta previa, 37% had VB and 15% had VB requiring delivery. Women with VB requiring delivery had significantly more episodes of VB than those who did not require delivery for VB (1.5, interquartile range [IQR] [1-3] vs 1.0 [1-5]; p = 0.001). In univariate analysis, women with VB had decreased CL (3.9 vs. 4.2 cm; p < 0.01) compared with those without. Women with VB requiring delivery had increased DPO (2.6 cm IQR [1.7-3.3] vs. 1.5 cm [1.1-2.4], p = 0.01) compared with those without. After adjusting for confounders, only CL < 4 cm remained independently associated with increased risk of VB (adjusted odds ratio: 2.27, 95% confidence interval [1.12-4.58], p = 0.01). None of the measures were predictive of either outcome (area under the curve < 0.65). CONCLUSION: Decreased CL may be associated with risk of VB in placenta previa. KEY POINTS: · Placenta previa is associated with VB.. · Sonographic markers of placenta previa are associated with VB.. · CL is associated with VB in placenta previa, whereas placental DPO is associated with higher rates of bleeding leading to delivery..

A multimodal deep learning model for predicting severe hemorrhage in placenta previa.

Placenta previa causes life-threatening bleeding and accurate prediction of severe hemorrhage leads to risk stratification and optimum allocation of interventions. We aimed to use a multimodal deep learning model to predict severe hemorrhage. Using MRI T2-weighted image of the placenta and tabular data consisting of patient demographics and preoperative blood examination data, a multimodal deep learning model was constructed to predict cases of intraoperative blood loss > 2000 ml. We evaluated the prediction performance of the model by comparing it with that of two machine learning methods using only tabular data and MRI images, as well as with that of two human expert obstetricians. Among the enrolled 48 patients, 26 (54.2%) lost > 2000 ml of blood and 22 (45.8%) lost < 2000 ml of blood. Multimodal deep learning model showed the best accuracy of 0.68 and AUC of 0.74, whereas the machine learning model using tabular data and MRI images had a class accuracy of 0.61 and 0.53, respectively. The human experts had median accuracies of 0.61. Multimodal deep learning models could integrate the two types of information and predict severe hemorrhage cases. The model might assist human expert in the prediction of intraoperative hemorrhage in the case of placenta previa.

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.

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.

Placenta accreta spectrum in major placenta previa diagnosed only by MRI: incidence, risk factors, and maternal morbidity.

BACKGROUND: Antenatal assessment of maternal risk factors and imaging evaluation can help in diagnosis and treatment of placenta accreta spectrum (PAS) in major placenta previa (PP). Recent evidence suggests that magnetic resonance imaging (MRI) could complement ultrasonography (US) in the PAS diagnosis. OBJECTIVES: Evaluate the incidence, risk factors, and maternal morbidity related to the MRI diagnosis of PAS in major PP. DESIGN: A 10-year retrospective cohort study. SETTING: Tertiary care hospital. PATIENTS AND METHODS: We report on patients with major PP who had cesarean delivery in Abha Maternity and Children's Hospital (AMCH) over a 10-year period (2012-2021). They were evaluated with ultrasonography (US) and color Doppler for evidence of PAS. Antenatal MRI was ordered either to confirm the diagnosis (if equivocal US) or to assess the depth of invasion/extra-uterine extension (if definitive US). MAIN OUTCOME MEASURES: Risk factors for PAS in major PP and maternal complications. SAMPLE SIZE: 299 patients RESULTS: Among 299 patients, MRI confirmed the PAS diagnosis in 91/299 (30.5%) patients. The independent risk factors for MRI diagnosis of PAS in major PP included only repeated cesarean sections and advanced maternal age. The commonest maternal morbidity in major PP with PAS was significantly excessive intraoperative bleeding. CONCLUSION: MRI may be a valuable adjunct in the evaluation of PAS in major PP; as a complement, but not substitute US. MRI may be suitable in major PP/PAS patients who are older and have repeated cesarean deliveries with equivocal results or deep/extra-uterine extension on US. LIMITATION: Single center, small sample size, lack of complete histopathological diagnosis. CONFLICT OF INTEREST: None.

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).

Utility of the angle between the cervical canal and the anatomical conjugate line for predicting pouch of Douglas obliteration in patients with posterior placenta previa.

AIM: Pouch of Douglas obliteration, which prevents exteriorization of the uterus, increases surgical morbidity in patients with placenta previa. We aimed to identify magnetic resonance imaging features that can predict pouch of Douglas obliteration preoperatively. METHODS: We retrospectively assessed 39 women with posterior placenta previa who underwent magnetic resonance imaging for the preoperative assessment of placenta accreta spectrum. We defined the angle formed by the anatomical conjugate line (based on pelvimetry) and the cervical canal as the cervical inclination angle, which was measured on sagittal T2-weighted magnetic resonance imaging. Subsequently, we analyzed the correlation between the cervical inclination angle and pouch of Douglas obliteration. RESULTS: The median maternal age was 34 years (range, 22-44 years) and 26 (66.7%) women delivered at term. The median cervical inclination angle was 98° (range, 71-128). Pouch of Douglas obliteration was confirmed in six patients (15.4%). The cut-off value of the cervical inclination angle for the prediction of pouch of Douglas obliteration was 102° with a sensitivity of 66.7%, specificity of 78.8%, positive predictive value of 36.4%, and negative predictive value of 92.9% (area under the curve, 0.83). CONCLUSIONS: Measuring the cervical inclination angle may help in ruling out an obliteration of the pouch of Douglas. It may also be useful in the operative management of women with posterior placenta previa. However, caution should be exercised when generalizing the results of this study because of the small sample size, which makes the results prone to bias.

Knowledge Gaps in Placenta Accreta Spectrum.

Since its first description early in the 20th Century, placenta accreta and its variants have changed substantially in incidence, risk factor profile, clinical presentation, diagnosis and management. While systematic use of diagnostic tools and a multidisciplinary team care approach has begun to improve patient outcomes, the condition's pathophysiology, epidemiology, and best practices for diagnosis and management remain poorly understood. The use of large databases with broadly accepted terminology and diagnostic criteria should accelerate research in this area. Future work should focus on non-traditional phenotypes, such as those without placenta previa-preventive strategies, and long term medical and emotional support for patients facing this diagnosis. KEY POINTS: · Placenta accreta spectrum research may be improved with standardized terminology and use of large databases.. · Placenta accreta prediction should move beyond ultrasound with the addition of biomarkers, and needs to extend to those without traditional risk factors.. · Future research should identify practices that can prevent future accreta development..

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

OBJECTIVE: To evaluate the diagnostic accuracy of ultrasound and in the diagnosis of Placenta accreta spectrum (PAS). DATA SOURCES: Screening of MEDLINE, CENTRAL, other bases from inception to February 2022 using the keywords related to placenta accreta, increta, percreta, morbidly adherent placenta, and preoperative ultrasound diagnosis. STUDY ELIGIBILITY CRITERIA: All available studies- whether were prospective or retrospective- including cohort, case control and cross sectional that involved prenatal diagnosis of PAS using 2D or 3D ultrasound with subsequent pathological confirmation postnatal were included. Fifty-four studies included 5307 women fulfilled the inclusion criteria, PAS was confirmed in 2025 of them. STUDY APPRAISAL AND SYNTHESIS METHODS: Extracted data included settings of the study, study type, sample size, participants characteristics and their inclusion and exclusion criteria, Type and site of placenta previa, Type and timing of imaging technique (2D, and 3D), severity of PAS, sensitivity and specificity of individual ultrasound criteria and overall sensitivity and specificity. RESULTS: The overall sensitivity was 0.8703, specificity was 0.8634 with -0.2348 negative correlation between them. The estimate of Odd ratio, negative likelihood ratio and positive likelihood ratio were 34.225, 0.155 and 4.990 respectively. The overall estimates of loss of retroplacental clear zone sensitivity and specificity were 0.820 and 0.898 respectively with 0.129 negative correlation. The overall estimates of myometrial thinning, loss of retroplacental clear zone, the presence of bridging vessels, placental lacunae, bladder wall interruption, exophytic mass, and uterovesical hypervascularity sensitivities were 0.763, 0.780, 0.659, 0.785, 0.455, 0.218 and 0.513 while specificities were 0.890, 0.884, 0.928, 0.809, 0.975, 0.865 and 0.994 respectively. CONCLUSIONS: The accuracy of ultrasound in diagnosis of PAS among women with low lying or placenta previa with previous cesarean section scars is high and recommended in all suspected cases. TRIAL REGISTRATION: Number CRD42021267501.

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.

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.

Perinatal assessment of complex cesarean delivery: beyond placenta accreta spectrum.

Multiple cesarean deliveries are known to be associated with long-term postoperative consequences because of a permanent defect of the lower uterine segment wall and the development of thick pelvic adhesions. Patients with a history of multiple cesarean deliveries often present with large cesarean scar defects and are at heightened risk in subsequent pregnancies of cesarean scar ectopic pregnancy, uterine rupture, low-lying placenta or placenta previa, and placenta previa accreta. Moreover, large cesarean scar defects will lead to progressive dehiscence of the lower uterine segment with the inability to effectively reapproximate hysterotomy edge and repair at birth. Major remodeling of the lower uterine segment associated with true placenta accreta spectrum at birth, whereby the placenta becomes inseparable from the uterine wall, increases the rates of perinatal morbidity and mortality, especially when undiagnosed before delivery. Ultrasound imaging is currently not routinely used to evaluate the surgical risks of patients with a history of multiple cesarean deliveries, beyond the risk assessment of placenta accreta spectrum. Independent of accreta placentation, a placenta previa under a scarred, thinned partially disrupted lower uterine segment, covered by thick adhesions with the posterior wall of the bladder, poses a surgical risk and requires fine dissection and surgical expertise; however, data on the use of ultrasound to evaluate uterine remodeling and adhesions between the uterus and other pelvic organs are scarce. In particular, transvaginal sonography has been underused, including in patients with a high probability of placenta accreta spectrum at birth. Based on the best available knowledge, we discuss the role of ultrasound imaging in identifying the signs suggestive of major remodeling of the lower uterine segment and in mapping the changes in the uterine wall and pelvis, to enable the surgical team to prepare for all different types of complex cesarean deliveries. The need for postnatal confirmation of the prenatal ultrasound findings for all patients with a history of multiple cesarean deliveries, regardless of the diagnosis of placenta previa and placenta accreta spectrum, is discussed. We propose an ultrasound imaging protocol and a classification of the level of surgical difficulty at elective cesarean delivery to stimulate further research toward the validation of ultrasound signs by which these signs may be applied to improve surgical outcomes.

Impact of Pelvic Rest Recommendations on Follow-Up and Resolution of Placenta Previa and Low-Lying Placenta.

OBJECTIVE: To determine the rate of resolution of placenta previa and low-lying placenta (LLP) and the effect of pelvic rest recommendations on the timing of follow-up imaging. METHODS: Retrospective review of pregnancies with previa/LLP detected on mid-trimester exam at our ultrasound unit from 2019 to 2021. LLP was defined as the lower edge of placenta located within 2 cm of the internal cervical os. Previa was defined as any portion of the placenta touching with the internal os. Demographics, placental location, activity restrictions, and delivery outcomes were analyzed. Timing of follow-up imaging was stratified by individuals advised and not advised pelvic rest. RESULTS: Exactly 144 patients had previa and 266 had LLP on the mid-trimester exam with complete records. Previa resolution happened in 51.4% (74/144) of cases. Exactly 62% (46/74) of previa resolutions occurred by the 28-week ultrasound. Exactly 45% (65/144) of previa patients were advised pelvic rest. Most pelvic rest and non-pelvic rest patients had a 28-week scan. Even when clearance occurred, most patients in both groups had a repeat ultrasound at 32 weeks. Exactly 75% of LLP resolved by the 28-week scan, and the remainder by delivery. Exactly 12% (32/259) of LLP patients were advised pelvic rest. CONCLUSION: Most societies recommend follow-up imaging at 32 weeks; however, our results suggest this may be done sooner and closer to 28 weeks. Pelvic rest did not affect timing of repeat imaging or delivery.