New insights into the etiopathology of placenta accreta spectrum

Emergency delivery in case of suspected placenta accreta spectrum: Can it be predicted?

INTRODUCTION

The main goal of placenta accreta spectrum (PAS) screening is to enable delivery in an expert center in the presence of an experienced team at an appropriate time. Our study aimed to identify independent risk factors for emergency deliveries within the IS-PAS 2.0 database cohort and establish a multivariate predictive model.

MATERIAL AND METHODS

A retrospective analysis of prospectively collected PAS cases from the IS-PAS database between January 2020 and June 2022 by 23 international expert centers was performed. All PAS cases (singleton and multiple pregnancies) managed according to local protocols were included. Individuals with emergent delivery were identified and compared to those with scheduled delivery. A multivariate analysis was conducted to identify the possible risk factors for emergency delivery and was used to establish a predictive model. Maternal outcomes were compared.

RESULTS

Overall, 315 women were included in the study. Of these, 182 participants (89 with emergent and 93 with scheduled delivery) were included in the final analysis after exclusion of those with unsuspected PAS antenatally or who lacked information about the urgency of delivery. Gestational age at delivery was higher in the scheduled group (34.7 vs. 32.9, p < 0.001). Antenatal bleeding (OR 2.9, p = 0.02) and a placenta located over a uterine scar (OR 0.38, p = 0.001) were the independent predictive factors for emergent delivery (AUC 0.68). Ultrasound (US) markers: loss of clear zone (p = 0.001), placental lacunae (p = 0.01), placental bulge (p = 0.02), and presence of bridging vessels (p = 0.02) were more frequently documented in the scheduled group. None of these markers improved the predictive values of the model. Higher PAS grades were identified in the scheduled group (p = 0.01). There were no significant differences in maternal outcomes.

CONCLUSIONS

Antenatal bleeding and the placental location away from the uterine scar remained the most significant predictors for emergent delivery among patients with PAS, even when combining more predictive risk factors, including US markers. Based on these results, patients who bleed antenatally may benefit from transfer to an expert center, as we found no differences in maternal outcomes between groups delivered in expert centers. Earlier-scheduled delivery is not supported due to the low predictive value of our model.

KLF6 negatively regulates HIF-1α in extravillous trophoblasts under hypoxia

INTRODUCTION

HIF-1α, the master regulator of hypoxia cellular response, is stabilized under low oxygen levels and degraded in the presence of oxygen but its transcription, translation, and degradation are tightly regulated by numerous pathways. KLF6 is a transcription factor involved in proliferation, differentiation, and apoptosis in several cell systems. Under hypoxia it is upregulated in a HIF-1α-dependent manner in extravillous trophoblasts. Considering the importance of hypoxia modulation of EVT behavior through HIF1-α we aimed to study whether KLF6 modulates HIF-1α expression in HTR8/SVneo cells.

METHODS

HTR8/SVneo cells were cultured in a 1 % oxygen chamber or in 3D format where a spontaneous oxygen gradient is generated. qRT-PCR and Western blot were performed to analyze mRNA and protein expression, respectively. SiRNA, shRNA, or plasmids were used to down- or up-regulate gene expression. Wound healing assay was performed under hypoxia to evaluate migration. The NFκB pathway was modulated with dominant negative mutants and a chemical inhibitor. Cobalt chloride was used to block HIF-1α degradation.

RESULTS

KLF6 up- and down-regulation in HTR8/SVneo cells exposed to acute hypoxia revealed a negative regulation on HIF-1α. KLF6 silencing led to a partially HIF-1α-dependent increase in MMP9 and VEGF. The NF-κB pathway and HIF-1α degradation were involved in KLF6-dependent HIF-1α regulation. HTR8/SVneo-3D culture showed that KLF6 negatively regulates HIF-1α in a microenvironment with naturally generated hypoxia.

DISCUSSION

Present results reveal that KLF6 contributes to a fine tune modulation of HIF-1α level under hypoxia. Thus, sustaining a HIF-1α homeostatic level, KLF6 might contribute to control EVT adaptation to hypoxia.

Risk factors for placenta accreta spectrum without prior cesarean section: A case-control study in China

OBJECTIVE

To identify the risk factors for placenta accreta spectrum (PAS) disorders in women without prior cesarean section (CS).

METHODS

This retrospective case-control study investigated patients without prior CS who gave birth at Peking University Third Hospital between January 1, 2015 and December 31, 2021. Patients diagnosed with PAS according to the clinical diagnostic criteria of the 2019 International Federation of Gynecology and Obstetrics (FIGO) classification were included as the study group. Patients were matched as the control group according to delivery date and placenta previa, in a 1:2 allocation ratio. Maternal characteristics were compared between the two groups.

RESULTS

The study included 348 patients in the study group and 696 in the control group. The multivariate analysis showed that the independent risk factors of PAS consisted of operative hysteroscopy (once: adjusted odds ratio [aOR] 2.38, 95% CI 1.28-4.24, P = 0.006; twice or more: aOR 5.43, 95% CI 1.04-28.32, P = 0.045), uterine curettage (once: aOR 2.54, 95% CI 1.80-3.58, P < 0.001; twice: aOR 3.01, 95% CI 1.81-5.02, P < 0.001; three or more times: aOR 9.18, 95% CI 4.64-18.18, P < 0.001), multifetal pregnancy (aOR 5.64, 95% CI 3.01-10.57, P < 0.001), adenomyosis (aOR 2.77, 95% CI 1.23-6.22, P = 0.014), in vitro fertilization (aOR 1.51, 95% CI 1.04-2.20, P = 0.030) and pre-eclampsia (aOR 2.72, 95% CI 1.36-5.45, P = 0.005), and the independent protective factor was being multiparous (aOR 0.37, 95% CI 0.25-0.54, P < 0.001).

CONCLUSION

After controlling the effect of placenta previa, we found that patients with PAS without prior CS had unique maternal characteristics. Classification and quantification of the intrauterine surgeries they have undergone is essential for identifying high-risk patients. Early identification of high-risk groups by risk factors has the potential to improve the prognosis considerably.

Clinical-sonographic scores for the screening of placenta accreta spectrum: a systematic review and meta-analysis

OBJECTIVE

Clinical-sonographic scoring systems combining clinical features and ultrasound imaging markers have been proposed for the screening of placenta accreta spectrum, but their usefulness in different settings remains limited. This study aimed to assess and compare different clinical-sonographic score systems applied from mid-pregnancy for the prenatal evaluation of patients at risk of placenta accreta spectrum at birth.

DATA SOURCES

PubMed/MEDLINE, Google Scholar, and Embase were searched between October 1982 and October 2022 to identify eligible studies.

STUDY ELIGIBILITY CRITERIA

Observational studies providing data on the use of a combined clinical-ultrasound score system applied from mid-pregnancy for the prenatal evaluation of placenta accreta spectrum were included.

METHODS

Study characteristics were evaluated by 2 independent reviewers using a predesigned protocol registered on PROSPERO (CRD42022332486). Heterogeneity among studies was analyzed with Cochran's Q-test and I2 statistics. Statistical heterogeneity was quantified by estimating the variance between the studies using I2 statistics. The area under the receiver operating characteristic curve of each score and their summary receiver operating characteristic curves were calculated with sensitivity and specificity, and the integrated score of the summaries of the receiver operating characteristic curves of all sonographic markers was calculated. Forest plots were used to develop the meta-analysis of each sonographic marker and for the integrated sonographic score.

RESULTS

Of 1028 articles reviewed, 12 cohorts and 2 case-control studies including 1630 patients screened for placenta accreta spectrum by clinical-ultrasound scores met the eligibility criteria. A diagnosis of placenta accreta spectrum was reported in 602 (36.9%) cases, for which 547 (90.9%) intraoperative findings and/or histopathologic data were described. A wide variation was observed among the studies in reported sensitivities and specificities and in thresholds used for the identification of patients with a high probability of placenta accreta spectrum at birth. The summaries of the areas under the curve of the individual sonographic scores ranged from 0.85 (the lowest) for subplacental hypervascularity to 0.91 for placental location in the lower uterine segment, myometrial thinning, and placental lacunae and 0.95 for the loss of clear zone. Only 4 studies included placental bulging in their sonographic score system, and therefore no meta-analysis for this score was performed. The integrated summary of the areas under the curve was 0.83 (95% confidence interval, 79-0.86). Forest plot analysis revealed integrated sensitivities and specificities of 0.68 (95% confidence interval, 0.53-0.80) and 0.88 (95% confidence interval, 0.68-0.96), respectively.

CONCLUSION

Clinical-sonographic score systems can contribute to the prenatal screening of patients at risk of placenta accreta spectrum at birth. Although we included multiple sonographic studies conducted during the mid-pregnancy period, standardized evaluation should be performed not only with strict ultrasound criteria for the placental position, mid third trimester gestational age at examination, and sonographic markers associated with PAS. Numeric sensitivities, specificities, NPVs, PPV, LR-, and LR+ should be recorded prospectively to assess their accuracy in different set-ups and PTP should be verified at delivery. The variables recommended for most predictive screening are: loss of clear zone underneath the placental bed, placentation in the LUS, and placenta lacunae.

Abnormal Placentation After Caesarean Section: A Retrospective Study

Introduction Caesarean section (CS) is a lifesaving operation; it can have many complications in subsequent pregnancies. Since the uterine wall and cavity are not normal after CS, the implantation and subsequent trophoblastic invasion and placenta formation may be affected. This study was carried out to find out implantation and placental problems encountered in subsequent pregnancies. The spectrum includes placenta accreta, increta, and percreta and is characterized microscopically by a complete or partial absence of decidua and placental adherence to or invasion of the myometrium. The study was performed to find out the complications of CS in subsequent pregnancies and take measures to detect them early and take appropriate action.  Materials and methods This retrospective study was carried out at Dr. D.Y. Patil Medical College and Research Centre Pimpri, Dr DY Patil Vidyapeeth, a large tertiary care centre. Many complications like placenta previa, adherent placenta, ectopic pregnancy, obstetrical hysterectomy, etc, the ones directly related to implantation and placentation, were recorded and compared with the literature. Results and observations The study was over a period of three years. During this period, there were 10,296 antenatal cases registered; of all the registered cases, 2,544 were cases of post-caesarean pregnancy. There were three cases of tubal ectopic pregnancy, two were diagnosed as the patients complained of amenorrhoea, spotting, and pain abdomen, confirmed on sonography and one was picked up on a routine first-trimester scan. There were two cases of scar ectopic pregnancy. Both the cases were diagnosed as threatened abortion initially and ultrasound confirmed the diagnosis; both were managed medically. Five cases of placenta previa were encountered. There were three cases of morbidly adherent placenta, and two cases underwent obstetrical hysterectomy. Conclusion All surgical procedures have become safe, but they all have some complications. Many complications in the next pregnancy after caesarean are life-threatening and dangerous. These complications should be detected early to prevent any catastrophic event.

Emergency delivery in pregnancies at high probability of placenta accreta spectrum on prenatal imaging: a systematic review and meta-analysis

BACKGROUND

Placenta accreta spectrum disorders are associated with a high risk of maternal morbidity, particularly when surgery is performed under emergency conditions. This study aimed to investigate the incidence of emergency cesarean delivery in patients with a high probability of placenta accreta spectrum disorders on prenatal imaging and to compare the maternal and neonatal outcomes between patients requiring emergency cesarean delivery and those not requiring emergency cesarean delivery.

DATA SOURCES

MEDLINE, Embase, Cochrane, and ClinicalTrials.gov databases were searched.

STUDY ELIGIBILITY CRITERIA

This study included case-control studies reporting the outcomes of pregnancies with a high probability of placenta accreta spectrum on prenatal imaging confirmed at birth delivered via unplanned emergency cesarean delivery vs those delivered via planned elective cesarean delivery for maternal or fetal indications. The outcomes observed were the occurrence of emergency cesarean delivery; incidence of placenta accreta and placenta increta/placenta percreta; preterm birth at <34 weeks of gestation; and indications for emergency delivery. This study analyzed and compared the outcomes between patients who underwent emergency cesarean delivery and those who underwent elective cesarean delivery, including estimated blood loss; number of packed red blood cell units transfused and blood products transfused; transfusion of more than 4 units of packed red blood cell; ureteral, bladder, or bowel injury; disseminated intravascular coagulation; relaparotomy after the primary surgery; maternal infection or fever; wound infection; vesicouterine or vesicovaginal fistula; admission to the neonatal intensive care unit; maternal death; composite neonatal morbidity; fetal or neonatal loss; Apgar score of <7 at 5 minutes; and neonatal birthweight.

METHODS

Quality assessment of the included studies was performed using the Newcastle-Ottawa Scale for case-control and cohort studies. Random-effect meta-analyses of proportions, risks, and mean differences were used to combine the data.

RESULTS

A total of 11 studies with 1290 pregnancies complicated by placenta accreta spectrum were included in the systematic review. Emergency cesarean delivery was reported in 36.2% of pregnancies (95% confidence interval, 28.1-44.9) with placenta accreta spectrum at birth, of which 80.3% of cases (95% confidence interval, 36.5-100.0) occurred before 34 weeks of gestation. The main indication for emergency cesarean delivery was antepartum bleeding, which complicated 61.8% of the cases (95% confidence interval, 32.1-87.4). Patients who underwent emergent cesarean delivery had higher estimated blood loss during surgery (pooled mean difference, 595 mL; 95% confidence interval, 116.10-1073.90; P<.001), higher number of packed red blood cells transfused (pooled mean difference, 2.3 units; 95% confidence interval, 0.99-3.60; P<.001), and higher number of blood products transfused (pooled mean difference, 3.0; 95% confidence interval, 1.10-4.90; P=.002) than patients who underwent scheduled cesarean delivery. Patients who underwent emergency cesarean delivery had a higher risk of requiring transfusion of more than 4 units of packed red blood cell (odds ratio, 3.8; 95% confidence interval, 1.7-4.9; P=.002), bladder injury (odds ratio, 2.1; 95% confidence interval, 1.1-4.0; P=.003), disseminated intravascular coagulation (odds ratio, 6.1; 95% confidence interval, 3.1-13.1; P<.001), and admission to the intensive care unit (odds ratio, 2.1; 95% confidence interval, 1.4-3.3; P<.001). Newborns delivered via emergency cesarean delivery had a higher risk of adverse composite neonatal outcomes (odds ratio, 2.6; 95% confidence interval, 1.4-4.7; P=.019), admission to the neonatal intensive care unit (odds ratio, 2.5; 95% confidence interval, 1.1-5.6; P=.029), Apgar score of <7 at 5 minutes (odds ratio, 2.7; 95% confidence interval, 1.5-4.9; P=.002), and fetal or neonatal loss (odds ratio, 8.2; 95% confidence interval, 2.5-27.4; P<.001).

CONCLUSION

Emergency cesarean delivery complicates approximately 35% of pregnancies affected by placenta accreta spectrum disorders and is associated with a higher risk of adverse maternal and neonatal outcomes. Large prospective studies are needed to evaluate the clinical and imaging signs that can identify patients with a high probability of placenta accreta spectrum at birth, patients at risk of requiring emergency cesarean delivery or peripartum hysterectomy, and patients at high risk of experiencing intrapartum hemorrhage.

Looking back to look forward: Has the time arrived for active management of obstetricians in placenta accreta spectrum?

Placenta accreta spectrum (PAS) is a relatively new obstetric condition which, until recently, was poorly understood. The true incidence is unknown because of the poor quality and heterogeneous diagnostic criteria. Classification systems have attempted to provide clarity on how to grade and diagnose PAS, but these are no longer reflective of our current understanding of PAS. This is particularly true for placenta percreta, which referred to extrauterine disease, as recent studies have demonstrated that placental villi associated with PAS have minimal potential to invade beyond the uterine serosa. It is accepted that PAS is a direct consequence of previous iatrogenic uterine injury, most commonly a previous cesarean section. Here, we "look back to look forwards"-starting with the primary predisposing factor for PAS, an iatrogenic uterine injury and subsequent wound healing. We then consider the evolution of definitions and diagnostic criteria of PAS from its first description over a century ago to current classifications. Finally, we discuss why modifications to the current classifications are needed to allow accurate diagnosis of this rare but life-threatening complication, while avoiding overdiagnosis and potential patient harm.

Evaluation of maternal serum protein biomarkers in the prenatal evaluation of placenta accreta spectrum: A systematic scoping review

INTRODUCTION

Placenta accreta spectrum (PAS) is an increasingly commonly reported condition due to the continuous increase in the rate of cesarean deliveries (CD) worldwide; however, the prenatal screening for pregnant patients at risk of PAS at birth remains limited, in particular when imaging expertise is not available.

MATERIAL AND METHODS

Two major electronic databases (MEDLINE and Embase) were searched electronically for articles published in English between October 1992 and January 2023 using combinations of the relevant medical subject heading terms and keywords. Two independent reviewers selected observational studies that provided data on one or more measurement of maternal blood-specific biomarker(s) during pregnancies with PAS at birth. PRISMA Extension for Scoping Review (PRISMA-ScR) was used to extract data and report results.

RESULTS

Of the 441 reviewed articles, 29 met the inclusion criteria reporting on 34 different biomarkers. 14 studies were retrospective and 15 prospective overall including 18 251 participants. Six studies had a cohort design and the remaining a case-control design. Wide clinical heterogeneity was found in the included studies. In eight studies, the samples were obtained in the first trimester; in five, the samples were collected on hospital admission for delivery; and in the rest, the samples were collected during the second and/or third trimester.

CONCLUSIONS

Measurements of serum biomarkers, some of which have been or are still used in screening for other pregnancy complications, could contribute to the prenatal evaluation of patients at risk of PAS at delivery; however, important evidence gaps were identified for suitable cutoffs for most biomarkers, variability of gestational age at sampling and the potential overlap of the marker values with other placental-related complications of pregnancy.

Development and validation of a nomogram for predicting placenta accreta spectrum in pregnancies with one previous cesarean delivery

OBJECTIVE

This study aimed to develop and validate a prenatal nomogram to predict the risk of placenta accreta spectrum (PAS) in women with one previous cesarean delivery.

METHODS

This retrospective study enrolled 5157 pregnant women with one previous cesarean delivery in China from January 2021 to January 2023. The nomogram was developed from a training cohort of 3612 pregnant women and tested on a validation cohort of 1545 pregnant women. Multivariate regression analysis was performed using the minimum value of the Akaike information criterion to select prognostic factors that can be included in the nomogram. We evaluated the nomogram by the area under the receiver operating characteristic (ROC) curve, calibration curves, and the decision curve analysis (DCA).

RESULTS

PAS occurred in 199 (5.51%) and 80 (5.18%) patients in the training and validation cohorts, respectively. Backward stepwise algorithms in the multivariable logistic regression model determined abortion, hypertensive disorders complicating pregnancy, fetal position, and placenta previa as relevant PAS predictors. The area under the ROC curve for the nomogram was 0.770 (95% confidence interval [CI] 0.733-0.807) and 0.791 (95% CI 0.730-0.853) for the training and validation cohorts, respectively. The calibration curves indicated that the nomogram's prediction probability was consistent with the actual probability. The DCA curve revealed that the nomogram has potential clinical benefit.

CONCLUSION

A prenatal nomogram was developed for PAS in our study, which helped obstetricians determine potential patients with PAS and make sufficient preoperative preparation to reduce maternal and neonatal complications.

Single-cell and spatial transcriptomics reveal alterations in trophoblasts at invasion sites and disturbed myometrial immune microenvironment in placenta accreta spectrum disorders

BACKGROUND

Placenta accreta spectrum disorders (PAS) are a severe complication characterized by abnormal trophoblast invasion into the myometrium. The underlying mechanisms of PAS involve a complex interplay of various cell types and molecular pathways. Despite its significance, both the characteristics and intricate mechanisms of this condition remain poorly understood.

METHODS

Spatial transcriptomics (ST) and single-cell RNA sequencing (scRNA-seq), were performed on the tissue samples from four PAS patients, including invasive tissues (ST, n = 3; scRNA-seq, n = 4), non-invasive normal placenta samples (ST, n = 1; scRNA-seq, n = 2). Three healthy term pregnant women provided normal myometrium samples (ST, n = 1; scRNA-seq, n = 2). ST analysis characterized the spatial expression landscape, and scRNA-seq was used to identify specific cellular components in PAS. Immunofluorescence staining was conducted to validate the findings.

RESULTS

ST slices distinctly showed the myometrium in PAS was invaded by three subpopulations of trophoblast cells, extravillous trophoblast cells, cytotrophoblasts, and syncytiotrophoblasts, especially extravillous trophoblast cells. The pathways enriched by genes in trophoblasts, smooth muscle cells (SMC), and immune cells of PAS were mainly associated with immune and inflammation. We identified elevated expression of the angiogenesis-stimulating gene PTK2, alongside the cell proliferation-enhancing gene EGFR, within the trophoblasts of PAS group. Trophoblasts mainly contributed the enhancement of HLA-G and EBI3 signaling, which is crucial in establishing immune escape. Meanwhile, SMC regions in PAS exhibited upregulation of immunomodulatory markers such as CD274, HAVCR2, and IDO1, with CD274 expression experimentally verified to be increased in the invasive SMC areas of the PAS group.

CONCLUSIONS

This study provided information of cellular composition and spatial organization in PAS at single-cell and spatial level. The dysregulated expression of genes in PAS revealed a complex interplay between enhanced immune escape in trophoblasts and immune tolerance in SMCs during invasion in PAS. These findings will enhance our understanding of PAS pathogenesis for developing potential therapeutic strategies.

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.

Current understanding of the pathogenesis of placenta accreta spectrum disorder with focus on mitochondrial function

AIM

The refinement of assisted reproductive technology, including the development of cryopreservation techniques (vitrification) and ovarian stimulation protocols, makes frozen embryo transfer (FET) an alternative to fresh ET and has contributed to the success of assisted reproductive technology. Compared with fresh ET cycles, FET cycles were associated with better in vitro fertilization outcomes; however, the occurrence of pregnancy-induced hypertension, preeclampsia, and placenta accreta spectrum (PAS) was higher in FET cycles. PAS has been increasing steadily in incidence as a life-threatening condition along with cesarean rates worldwide. In this review, we summarize the current understanding of the pathogenesis of PAS and discuss future research directions.

METHODS

A literature search was performed in the PubMed and Google Scholar databases.

RESULTS

Risk factors associated with PAS incidence include a primary defect of the decidua basalis or scar dehiscence, aberrant vascular remodeling, and abnormally invasive trophoblasts, or a combination thereof. Freezing, thawing, and hormone replacement manipulations have been shown to affect multiple cellular pathways, including cell proliferation, invasion, epithelial-to-mesenchymal transition (EMT), and mitochondrial function. Molecules involved in abnormal migration and EMT of extravillous trophoblast cells are beginning to be identified in PAS placentas. Many of these molecules were also found to be involved in mitochondrial biogenesis and dynamics.

CONCLUSION

The etiology of PAS may be a multifactorial genesis with intrinsic predisposition (e.g., placental abnormalities) and certain environmental factors (e.g., defective decidua) as triggers for its development. A distinctive feature of this review is its focus on the potential factors linking mitochondrial function to PAS development.

Placenta accreta spectrum conservative management and coagulopathy: case series and systematic review

OBJECTIVE

Management of placenta accreta spectrum (PAS) with the placenta kept in situ aims to preserve fertility and minimize blood loss. However, this method is associated with a risk of coagulopathy and subsequent bleeding. The aim of this study was to evaluate the occurrence and pathophysiology of coagulopathy in cases of PAS managed conservatively.

METHODS

We reviewed our database for cases of PAS in which the placenta was kept in situ. In addition, we performed a systematic review of articles on PAS in which the placenta was left in situ and was complicated by coagulopathy. PubMed was searched for publications between 1980 and 2023. Our eligibility criteria included studies in which no additional interventions were performed other than keeping the placenta entirely in situ, and in which coagulopathy was reported.

RESULTS

After screening and selection of full-text articles, 10 studies were included in the review. A review of our databases yielded a case series of PAS managed conservatively with the placenta kept in situ. When adding our case series to the results of our systematic review, a total of 87 cases were found to have been managed conservatively, with 28 cases of coagulopathy. Of these, the time at which coagulopathy developed was known in 11 cases. The median time at development of coagulopathy was 58 (interquartile range, 50-67) days postpartum.

CONCLUSIONS

Our findings highlight that conservative management of PAS with the placenta in situ poses a risk of coagulopathy. Keeping the placenta in situ after delivery prolongs the risk factors that are integral to PAS. The pathophysiology behind coagulopathy is comparable with that of concealed placental abruption, due to the disrupted uteroplacental interface and the collection of blood in the placenta. Therefore, the presence of large placental lakes could be an indicator of developing coagulopathy. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Evaluation of preoperative ultrasound signs associated with bladder injury during complex Cesarean delivery: case-control study

OBJECTIVE

Intraoperative hemorrhage and peripartum hysterectomy are the main complications in patients presenting with a low-lying placenta or placenta previa undergoing repeat Cesarean delivery (CD). Patients with a high probability of placenta accreta spectrum (PAS) at birth also have a higher risk of intraoperative urologic injury. The aim of this study was to evaluate the ultrasound signs and intraoperative features associated with these injuries.

METHODS

This was a retrospective case-control study of consecutive singleton pregnancies included in a prospective cohort of patients with a history of at least one prior CD and diagnosed prenatally with an anterior low-lying placenta or placenta previa at 32-36 weeks' gestation. All patients underwent investigational preoperative transabdominal and transvaginal ultrasound examination within 48 h prior to delivery. Ultrasound anomalies of uterine contour and uteroplacental vascularity, and gross anomalies of the lower uterine segment (LUS) and surrounding pelvic tissue at delivery, were recorded using a standardized protocol, which included evaluation of the extent of uterine contour anomalies. The diagnosis of PAS was established when one or more placental lobules could not be separated digitally from the uterine wall at delivery or during the gross examination of the hysterectomy or partial myometrial resection specimens, and was confirmed by histopathology. Data were compared between cases complicated by intraoperative bladder injury and controls from the same cohort matched at a 1:3 ratio by parity and the number of prior CDs using conditional logistic regression.

RESULTS

There were 16 (9.4%) patients with an intraoperative bladder injury in a cohort of 170 managed by the same multidisciplinary team during the study period. There were no patients diagnosed with ureteric or bladder trigone damage. There were 14 (87.5%) patients with a bladder injury that had histopathologic evidence of PAS at birth, including 11 (68.8%) cases described on microscopic examination as placenta increta and three (18.8%) as placenta creta. There was a significant (P = 0.03) difference between cases and controls in the distribution of intraoperative LUS vascularity, whereby the higher the number of enlarged vessels, the higher the odds of bladder injury. Multivariable regression analysis revealed that both gestational age at delivery and LUS remodeling on transabdominal ultrasound were associated with bladder injury. A higher gestational age was associated with a lower risk of injury. A higher LUS remodeling grade on transabdominal ultrasound was associated with an increased risk of bladder injury. Patients with Grade-3 remodeling (involving > 50% of the LUS) had 9-times higher odds of a bladder injury compared to patients with Grade-1 remodeling (involving < 30% of the LUS).

CONCLUSIONS

Preoperative ultrasound examination is useful in the evaluation of the risk of intraoperative bladder injury in patients with a history of prior CD presenting with a low-lying placenta or placenta previa. The larger the remodeling of the LUS on transabdominal ultrasound, the higher the risk of adverse urologic events. © 2024 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Risk factors for placenta accreta spectrum in pregnancies conceived after frozen-thawed embryo transfer in a hormone replacement cycle

OBJECTIVE

Assisted reproductive technology (ART), especially frozen-thawed embryo transfer (FET) in a hormone replacement cycle (HRC), is a risk factor for placenta accreta spectrum (PAS). This study aimed to clarify the risk factors for PAS related to the maternal background and ART techniques in pregnancies achieved after FET in an HRC.

STUDY DESIGN

We performed a case-control study in two tertiary perinatal centres in Japan. Among 14,028 patients who delivered at ≥24 weeks of gestation or were transferred after delivery to two tertiary perinatal centres between 2010 and 2021, 972 conceived with ART and 13,056 conceived without ART. PAS was diagnosed on the basis of the FIGO classification for the clinical diagnosis of PAS or retained products of conception after delivery at ≥24 weeks of gestation. We excluded women with fresh embryo transfer, FET with a spontaneous ovulatory cycle, a donor oocyte cycle, and missing details of the ART treatment. Finally, among women who conceived after FET in an HRC, 62 with PAS and 340 without PAS were included in this study. Multivariate logistic regression models were used for case-control comparisons, with adjustment for maternal age at delivery, parity, endometriosis or adenomyosis, the number of previous uterine surgeries of caesarean section, myomectomy, endometrial polypectomy or endometrial curettage, placenta previa, the stage of transferred embryos, and endometrial thickness at the initiation of progestin administration.

RESULTS

PAS was associated with ≥2 previous uterine surgeries (adjusted odds ratio, 3.57; 95 % confidence interval, 1.60-7.97) and the stage of embryo transfer (blastocysts: adjusted odds ratio, 2.89; 95 % confidence interval, 1.15-7.26). In patients with <2 previous uterine surgeries, PAS was associated with an endometrial thickness of <7.0 mm (adjusted odds ratio, 5.18; 95 % confidence interval, 1.10-24.44).

CONCLUSION

Multiple uterine surgeries and the transfer of blastocysts are risk factors for PAS in pregnancies conceived after FET in an HRC. In women with <2 previous uterine surgeries, a thin endometrium before FET is also a risk factor for PAS in these pregnancies.

Pathologic maternal and neonatal outcomes associated with programmed embryo transfer

PURPOSE

In this first of two companion papers, we critically review the evidence recently published in the primary literature, which addresses adverse maternal and neonatal pregnancy outcomes associated with programmed embryo transfer cycles. We next consider whether these pathological pregnancy outcomes might be attributable to traditional risk factors, unknown parental factors, embryo culture, culture duration, or cryopreservation. Finally, in the second companion article, we explore potential etiologies and suggest strategies for prevention.

METHODS

Comprehensive review of primary literature.

RESULTS

The preponderance of retrospective and prospective observational studies suggests that increased risk for hypertensive disorders of pregnancy (HDP) and preeclampsia in assisted reproduction involving autologous embryo transfer is associated with programmed cycles. For autologous frozen embryo transfer (FET) and singleton live births, the risk of developing HDP and preeclampsia, respectively, was less for true or modified natural and stimulated cycles relative to programmed cycles: OR 0.63 [95% CI (0.57-0.070)] and 0.44 [95% CI (0.40-0.50)]. Though data are limited, the classification of preeclampsia associated with programmed autologous FET was predominantly late-onset or term disease. Other adverse pregnancy outcomes associated with autologous FET, especially programmed cycles, included increased prevalence of large for gestational age infants and macrosomia, as well as higher birth weights. In one large registry study, FET was associated with fetal overgrowth of a symmetrical nature. Postterm birth and placenta accreta not associated with prior cesarean section, uterine surgery, or concurrent placenta previa were also associated with autologous FET, particularly programmed cycles. The heightened risk of these pathologic pregnancy outcomes in programmed autologous FET does not appear to be attributable to traditional risk factors, unknown parental factors, embryo culture, culture duration, or cryopreservation, although the latter may contribute a modest degree of increased risk for fetal overgrowth and perhaps HDP and preeclampsia in FET irrespective of the endometrial preparation.

CONCLUSIONS

Programmed autologous FET is associated with an increased risk of several, seemingly diverse, pathologic pregnancy outcomes including HDP, preeclampsia, fetal overgrowth, postterm birth, and placenta accreta. Though the greater risk for preeclampsia specifically associated with programmed autologous FET appears to be well established, further research is needed to substantiate the limited data currently available suggesting that the classification of preeclampsia involved is predominately late-onset or term. If substantiated, then this knowledge could provide insight into placental pathogenesis, which has been proposed to differ between early- and late-onset or term preeclampsia (see companion paper for a discussion of potential mechanisms). If a higher prevalence of preeclampsia with severe features as suggested by some studies is corroborated in future investigations, then the danger to maternal and fetal/neonatal health is considerably greater with severe disease, thus increasing the urgency to find preventative measures. Presupposing significant overlap of these diverse pathologic pregnancy outcomes within subjects who conceive by programmed embryo transfer, there may be common etiologies.

Evaluation of maternal serum thiol and ischemia-modified albumin levels in cases of placenta previa: A case-control study in a tertiary center

AIM

We aim to compare the maternal serum thiol and ischemia-modified albumin (IMA) levels between pregnant women with placenta previa and those with uncomplicated pregnancies and to determine whether changes in these levels were useful in predicting cases of abnormally invasive placenta (AIP).

METHODS

Fifty-five pregnant women diagnosed with placenta previa according to the diagnostic criteria (case group) were compared to 100 women with uncomplicated pregnancies of similar demographic characteristics (control group). The patients with placenta previa were further divided into two subgroups: AIP (n = 20) and placenta previa without invasion (n = 35). The maternal serum native thiol, total thiol, disulfide, and IMA levels of the groups were evaluated.

RESULTS

The native thiol, total thiol, and IMA values were significantly lower in the case group than in the control group (p < 0.001). The disulfide values were similar between the study and control groups (p = 0.488). When the AIP and placenta previa without invasion groups were compared, the levels of native thiol, total thiol, disulfide, and IMA were similar (p > 0.05).

CONCLUSIONS

Maternal serum thiol and IMA levels were lower in placenta previa cases compared to the control group. However, these parameters were not useful in predicting AIP cases.

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.

Material properties of nonpregnant and pregnant human uterine layers

The uterus has critical biomechanical functions in pregnancy and undergoes dramatic material growth and remodeling from implantation to parturition. The intrinsic material properties of the human uterus and how they evolve in pregnancy are poorly understood. To address this knowledge gap and assess the heterogeneity of these tissues, the time-dependent material properties of all human uterine layers were measured with nanoindentation. The endometrium-decidua layer was found to be the least stiff, most viscous, and least permeable layer of the human uterus in nonpregnant and third-trimester pregnant tissues. In pregnancy, the endometrium-decidua becomes stiffer and less viscous with no material property changes observed in the myometrium or perimetrium. Additionally, uterine material properties did not significantly differ between third-trimester pregnant tissues with and without placenta accreta. The foundational data generated by this study will facilitate the development of physiologically accurate models of the human uterus to investigate gynecologic and obstetric disorders.

Determination of biomarker candidates for the placenta accreta spectrum by plasma proteomic analysis

Placenta accreta spectrum (PAS) presents a significant obstetric challenge, associated with considerable maternal and fetal-neonatal morbidity and mortality. Nevertheless, it is imperative to acknowledge that a noteworthy subset of PAS cases remains undetected until the time of delivery, thereby contributing to an augmented incidence of morbidity among the affected individuals. The delayed identification of PAS not only hinders timely intervention but also exacerbates the associated health risks for both the maternal and fetal outcomes. This underscores the urgency to innovate strategies for early PAS diagnosis. In this study, we aimed to explore plasma proteins as potential diagnostic biomarkers for PAS. Integrated transcriptome and proteomic analyses were conducted to establish a novel diagnostic approach. A cohort of 15 pregnant women diagnosed with PAS and delivering at Inonu University Faculty of Medicine between 01/04/2021 and 01/01/2023, along with a matched control group of 15 pregnant women without PAS complications, were enrolled. Plasma protein identification utilized enzymatic digestion and liquid chromatography-tandem mass spectrometry techniques. Proteomic analysis identified 228 plasma proteins, of which 85 showed significant differences (P < 0.001) between PAS and control cases. We refined this to a set of 20 proteins for model construction, resulting in a highly accurate classification model (96.9% accuracy). Notable associations were observed for proteins encoded by P01859 (Immunoglobulin heavy constant gamma 2), P02538 (Keratin type II cytoskeletal 6A), P29622 [Kallistatin (also known as Serpin A4)], P17900 (Ganglioside GM2 activator Calmodulin-like protein 5), and P01619 (Immunoglobulin kappa variable 3-20), with fold changes indicating their relevance in distinguishing PAS from control groups. In conclusion, our study has identified novel plasma proteins that could serve as potential biomarkers for early diagnosis of PAS in pregnant women. Further research and validation in larger PAS cohorts are necessary to determine the clinical utility and reliability of these proteomic biomarkers for diagnosing PAS.

Risk factors of massive blood transfusion (MTP) in cesarean hysterectomy for placenta accreta spectrum

BACKGROUND

Placenta Accreta Spectrum (PAS) represents a particularly morbid condition for which blood transfusion is the leading cause. Delivery by cesarean hysterectomy is recommended for the management of PAS. Massive Transfusion Protocols (MTP) in obstetrics vary in definition and implementation. Given the significant blood loss during PAS cesarean hysterectomy, this is particularly important for surgeons and blood banks. Our objective was to identify risk factors for MTP in patients with antenatally suspected PAS.

METHODS

We performed a case-control study over a 11-year period from 2012 to 2022 at our center for Placenta Accreta Spectrum. MTP was defined by two methods, >4 units or > 10 units of red blood cells/whole blood transfused over 24 h. Antenatal, operative and post-operative outcomes were obtained from electronic medical records of these cases.

RESULTS

During the study time frame, 142 cases were managed by our PAS team and met all criteria. 85 % (120/142) of patients were transfused at least 1 unit of blood, 64 patients (45 %) received 0-3 units of blood, 50 patients (35 %) received 4-9 units of blood and 28 patients (19.7 %) were transfused > 10 units of blood. Pre-delivery vaginal bleeding, preterm labor and delivery < 34 weeks were independently significant in transfused patients. ROC analysis revealed an area under the curve (AUC) of 0.79 (p < 0.0001) in patients transfused > 10 units, showing predictive capability for this subgroup.

DISCUSSION

We here report pre-operative risk factors for MTP in patients undergoing cesarean hysterectomy for PAS. This allows for both resource utilization and patient counseling for this morbid maternal condition.

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.

Serum exosomal microRNA pathway activation in placenta accreta spectrum: pathophysiology and detection

BACKGROUND

Placenta accreta spectrum disorders are a complex range of placental pathologies that are associated with significant maternal morbidity and mortality. A diagnosis of placenta accreta spectrum relies on ultrasonographic findings with modest positive predictive value. Exosomal microRNAs are small RNA molecules that reflect the cellular processes of the origin tissues.

OBJECTIVE

We aimed to explore exosomal microRNA expression to understand placenta accreta spectrum pathology and clinical use for placenta accreta spectrum detection.

STUDY DESIGN

This study was a biomarker analysis of prospectively collected samples at 2 academic institutions from 2011 to 2022. Plasma specimens were collected from patients with suspected placenta accreta spectrum, placenta previa, or repeat cesarean deliveries. Exosomes were quantified and characterized by nanoparticle tracking analysis and western blotting. MicroRNA were assessed by polymerase chain reaction array and targeted single quantification. MicroRNA pathway analysis was performed using the Ingenuity Pathway Analyses software. Placental biopsies were taken from all groups and analyzed by polymerase chain reaction and whole cell enzyme-linked immunosorbent assay. Receiver operating characteristic curve univariate analysis was performed for the use of microRNA in the prediction of placenta accreta spectrum. Clinically relevant outcomes were collected from abstracted medical records.

RESULTS

Plasma specimens were analyzed from a total of 120 subjects (60 placenta accreta spectrum, 30 placenta previa, and 30 control). Isolated plasma exosomes had a mean size of 71.5 nm and were 10 times greater in placenta accreta spectrum specimens (20 vs 2 particles/frame). Protein expression of exosomes was positive for intracellular adhesion molecule 1, flotilin, annexin, and CD9. MicroRNA analysis showed increased detection of 3 microRNAs (mir-92, -103, and -192) in patients with placenta accreta spectrum. Pathway interaction assessment revealed differential regulation of p53 signaling in placenta accreta spectrum and of erythroblastic oncogene B2 or human epidermal growth factor 2 in control specimens. These findings were subsequently confirmed in placental protein analysis. Placental microRNA paralleled plasma exosomal microRNA expression. Biomarker assessment of placenta accreta spectrum signature microRNA had an area under the receiver operating characteristic curve of 0.81 (P<.001; 95% confidence interval, 0.73-0.89) with a sensitivity and specificity of 89.2% and 80%, respectively.

CONCLUSION

In this large cohort, plasma exosomal microRNA assessment revealed differentially expressed pathways in placenta accreta spectrum, and these microRNAs are potential biomarkers for the detection of placenta accreta spectrum.

Features of MR signals of retroplacental basal decidual space and its diagnostic significance

BACKGROUND

With more pregnant women undergoing cesarean section, the number of women with scarring in the uterus undergoing uterine magnetic resonance (MR) examination in the second and third trimesters following a subsequent pregnancy, has increased.

OBJECTIVE

To investigate features of MR signals in retroplacental basal decidual space.

METHODS

The MR imaging data of patients with clinically and pathologically confirmed placenta implantation and complete placental abruption were retrospectively analyzed.

RESULTS

Patients with high-intensity signals in T2-weighted images (T2WI) of the retroplacental basal decidual space did not suffer placenta implantation after delivery, while high-intensity signals in T2WI of the retroplacental basal decidual space was not observed in patients with different degrees of placenta implantation.

CONCLUSION

As the retroplacental basal decidual space is the barrier between the placenta and myometrium, high-intensity signals in T2WI can improve the confidence of MR exclusion diagnostics of placenta implantation, and can be used as exclusion criteria for MR diagnosis of placenta implantation.

Material Properties of Nonpregnant and Pregnant Human Uterine Layers

The uterus has critical biomechanical functions in pregnancy and undergoes dramatic material growth and remodeling from implantation to parturition. The intrinsic material properties of the human uterus and how they evolve in pregnancy are poorly understood. To address this knowledge gap and assess the heterogeneity of these tissues, the time-dependent material properties of all human uterine layers were measured with nanoindentation. The endometrium-decidua layer was found to be the least stiff, most viscous, and least permeable layer of the human uterus in nonpregnant and third-trimester pregnant tissues. In pregnancy, endometrium-decidua becomes stiffer and less viscous with no material property changes observed in the myometrium or perimetrium. Additionally, uterine material properties did not significantly differ between third-trimester pregnant tissues with and without placenta accreta. The foundational data generated by this study will facilitate the development of physiologically accurate models of the human uterus to investigate gynecologic and obstetric disorders.

Subsequent pregnancy outcomes and risk factors following conservative treatment for placenta accreta spectrum: a retrospective cohort study

BACKGROUND

Placenta accreta spectrum can lead to uncontrollable massive hemorrhage in the perinatal period. Currently, the first-line treatment for placenta accreta spectrum recommended worldwide is hysterectomy. However, adverse outcomes after hysterectomy, including surgical complications, such as difficulty in performing the procedure, and sequelae, such as infertility and psychological issues, cannot be ignored. Several surgical approaches for conservative treatment have been proposed. There are few reports on the effectiveness, safety, and long-term complications of conservative treatments, especially subsequent pregnancy outcomes.

OBJECTIVE

This study aimed to investigate the clinical outcomes and identify risk factors of subsequent pregnancies among patients with placenta accreta spectrum who had undergone conservative surgery.

STUDY DESIGN

This was a retrospective cohort study of subsequent pregnancy cases after cesarean delivery with conservative treatment for placenta accreta spectrum from 2011 to 2019 at The First Affiliated Hospital of Zhengzhou University to identify clinical outcomes of subsequent pregnancies and the risk factors of adverse pregnancy outcomes.

RESULTS

A total of 883 patients undergoing conservative surgery were included in this study, among which 604 (68.4%) were successfully followed up. There were 75 successful pregnancies in 72 patients, including 22 full-term or near-term deliveries, 1 induced labor in the second trimester of pregnancy, 6 cesarean scar pregnancies (8.0%), 2 ectopic pregnancies, and 44 first-trimester pregnancies (3 miscarriages and 41 elective abortions and 12 medical abortions and 32 vacuum aspirations). All newborns survived in the 22 full-term or near-term deliveries. Moreover, 5 placenta accreta spectrum cases (22.7%) and 6 placenta previa cases were observed. Postpartum hemorrhage was observed in 2 cases, with an incidence rate of 9.1%. All parameters, including age at subsequent pregnancy, gravidity, number of cesarean deliveries, type of previous placenta accreta spectrum, gestational week of pregnancy termination, interpregnancy interval, and the use of vascular occlusion techniques, were not found to be associated with recurrent placenta accreta spectrum and cesarean scar pregnancy.

CONCLUSION

Our findings show that treatment for placenta accreta spectrum does not automatically preclude a subsequent pregnancy. However, patients should be fully informed about the risk of recurrent placenta accreta spectrum, scar pregnancy, and postpartum hemorrhage.

The Association of Serum Midkine Level with Invasion in Placenta Previa: A Case-Control Study from a Tertiary Reference Center

We aimed to examine the relationship between serum midkine levels and placental invasion in pregnant women with placenta previa. The study group consisted of 43 pregnant women diagnosed with placenta previa, whereas the control group consisted of 60 healthy pregnant women. Serum midkine levels were compared between pregnant women with placenta previa and the control group in this study's first part. Thereafter, the utility of midkine in the prediction of the abnormally invasive placenta (AIP) was investigated and optimal cutoff values were calculated. Significantly higher serum midkine level was observed in placenta previa cases than in the controls (1.16 ng/mL vs. 0.18 ng/mL, P < 0.001). Serum midkine level was also significantly higher in the AIP group among the placenta previa cases (P = 0.004). In the receiver operating characteristic analysis, the cutoff value of the midkine level in predicting AIP was 1.19 ng/mL. This study revealed that the serum midkine level is higher in pregnant women with AIP. Maternal serum midkine level may be used as a complementary biomarker to the radiological and clinical findings for the prediction of the AIP in placenta previa cases.

Stromal cells-specific retinoic acid determines parturition timing at single-cell and spatial-temporal resolution

The underlying mechanisms governing parturition remain largely elusive due to limited knowledge of parturition preparation and initiation. Accumulated evidences indicate that maternal decidua plays a critical role in parturition initiation. To comprehensively decrypt the cell heterogeneity in decidua approaching parturition, we investigate the roles of various cell types in mouse decidua process and reveal previously unappreciated insights in parturition initiation utilizing single-cell RNA sequencing (scRNA-seq). We enumerate the cell types in decidua and identity five different stromal cells populations and one decidualized stromal cells. Furthermore, our study unravels that stromal cells prepare for parturition by regulating local retinol acid (RA) synthesis. RA supplement decreases expression of extracellular matrix-related genes in vitro and accelerates the timing of parturition in vivo. Collectively, the discovery of contribution of stromal cells in parturition expands current knowledge about parturition and opens up avenues for the intervention of preterm birth (PTB).

Adipocytes in the Uterine Wall during Experimental Healing and in Cesarean Scars during Pregnancy

We have suggested that adipocytes in uterine scars may affect the development of the placenta accrete spectrum (PAS). In the experimental part, we explored adipocytes in the uterine wall by the twelfth sexual cycle after surgery. In the clinical part, we investigated adipocyte clusters in the cesarean scar of pregnant women with and without PAS. The uterine wall was evaluated in gross and histological sections using morphometry, histochemistry (hematoxylin and eosin stain, Mallory stain), and immunohistochemistry for FABP4 (adipocyte markers), CD68, CD163, CD206 (macrophages), CD 34 (endothelium), cytokeratin 8 (epithelium), aSMA (smooth muscle cells). The design included an experimental study on Sprague-Dawley rats (n = 18) after a full-thickness surgical incision on the seventh (n = 6), 30th (n = 6), and 60th day (n = 6). The clinical groups include pregnant women without uterine scars (n = 10), pregnant women with a uterine scar after previous cesarean sections (n = 10), and women with PAS (n = 11). Statistical processing was carried out using nonparametric methods. Comparisons were conducted using the Mann-Whitney U-test and Kruskal-Wallis test. Statistical significance was considered at p < 0.05. On the seventh day, the rat uterine horn was enveloped by adipose tissue, which contained crown-like structures with FABP4+, CD68+, CD206+, and CD163+ cells. FABP4+ cells in the uterine wall were absent by the 30th day. The number of CD206+ and CD163+ cells in the adipose tissue decreased by the 30th day. On the 60th day, the attachment of fat tissue was revealed in the form of single strands. The serous layer around the damaged area totally recovered on the 60th day. FABP4+ cells were not detected in the uterine wall samples from pregnant women without a previous cesarean section. Adipocytes were found in the scar during non-complicated pregnancy and with PAS. Reducing the number of CD68+ cells in adipocyte clusters, there were in myometrium with PAS. Increased CD206+ and CD163+ cells were revealed in uterine adipocyte clusters of the group. According to the experimental finding, adipocytes should be absent in the uterine wall by the 12th sexual cycle after a full-thickness surgical incision. The presence of adipocyte clusters in cesarean scar indicated the disturbance of cell interaction. Differences in the numbers of CD206 and CD163 cells in adipocyte clusters between groups with and without PAS may be indirect evidence that uterine adipocytes affect the development of PAS.

Segmentation methods applied to MRI-derived radiomic analysis for the prediction of placenta accreta spectrum in patients with placenta previa

PURPOSE

To retrospectively evaluate the performance of different manual segmentation methods of placenta MR images for predicting Placenta Accreta Spectrum (PAS) disorders in patients with placenta previa (PP) using a Machine Learning (ML) Radiomics analysis.

METHODS

64 patients (n=41 with PAS and n= 23 without PAS) with PP who underwent MRI examination for suspicion of PAS were retrospectively selected. All MRI examinations were acquired on a 1.5 T using T2-weighted (T2w) sequences on axial, sagittal and coronal planes. Ten different manual segmentation methods were performed on sagittal placental T2-weighted images obtaining five sets of 2D regions of interest (ROIs) and five sets of 3D volumes of interest (VOIs) from each patient. In detail, ROIs and VOIs were positioned on the following areas: placental tissue, retroplacental myometrium, cervix, placenta with underneath myometrium, placenta with underneath myometrium and cervix. For feature stability testing, the same process was repeated on 30 randomly selected placental MRI examinations by two additional radiologists, working independently and blinded to the original segmentation. Radiomic features were extracted from all available ROIs and VOIs. 100 iterations of 5-fold cross-validation with nested feature selection, based on recursive feature elimination, were subsequently run on each ROI/VOI to identify the best-performing method to classify instances correctly.

RESULTS

Among the segmentation methods, the best performance in predicting PAS was obtained by the VOIs covering the retroplacental myometrium (Mean validation score: 0.761, standard deviation: 0.116).

CONCLUSION

Our preliminary results show that the VOI including the retroplacental myometrium using T2w images seems to be the best method when segmenting images for the development of ML radiomics predictive models to identify PAS in patients with PP.

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.

The role of transvaginal ultrasound in the third-trimester evaluation of patients at high risk of placenta accreta spectrum at birth

BACKGROUND

Transvaginal ultrasound imaging has become an essential tool in the prenatal evaluation of the lower uterine segment and anatomy of the cervix, but there are only limited data on the role of transvaginal ultrasound in the management of patients at high risk of placenta accreta spectrum at birth.

OBJECTIVE

This study aimed to evaluate the role of transvaginal sonography in the third trimester of pregnancy in predicting outcomes in patients with a high probability of placenta accreta spectrum at birth.

STUDY DESIGN

This was a retrospective analysis of prospectively collected data of patients presenting with a singleton pregnancy and a history of at least 1 previous cesarean delivery and patients diagnosed prenatally with an anterior low-lying placenta or placenta previa delivered electively after 32 weeks of gestation. All patients had a least 1 detailed ultrasound examination, including transabdominal and transvaginal scans, within 2 weeks before delivery. Of note, 2 experienced operators, blinded to the clinical data, were asked to make a judgment on the likelihood of placenta accreta spectrum as a binary, low or high-probability of placenta accreta spectrum, and to predict the main surgical outcome (conservative vs peripartum hysterectomy). The diagnosis of accreta placentation was confirmed when one or more placental cotyledons could not be digitally separated from the uterine wall at delivery or during the gross examination of the hysterectomy or partial myometrial resection specimens.

RESULTS

A total of 111 patients were included in the study. Abnormal placental tissue attachment was found in 76 patients (68.5%) at birth, and histologic examination confirmed superficial villous attachment (creta) and deep villous attachment (increta) in 11 and 65 cases, respectively. Of note, 72 patients (64.9%) had a peripartum hysterectomy, including 13 cases with no evidence of placenta accreta spectrum at birth because of failure to reconstruct the lower uterine segment and/or excessive bleeding. There was a significant difference in the distribution of placental location (X2=12.66; P=.002) between transabdominal and transvaginal ultrasound examinations, but both ultrasound techniques had similar likelihood scores in identifying accreta placentation that was confirmed at birth. On transabdominal scan, only a high lacuna score was significantly associated (P=.02) with an increased chance of hysterectomy, whereas on transvaginal scan, significant associations were found between the need for hysterectomy and the thickness of the distal part of the lower uterine segment (P=.003), changes in the cervix structure (P=.01), cervix increased vascularity (P=.001), and the presence of placental lacunae (P=.005). The odds ratio for peripartum hysterectomy were 5.01 (95% confidence interval, 1.25-20.1) for a very thin (<1-mm) distal lower uterine segment and 5.62 (95% confidence interval, 1.41-22.5) for a lacuna score of 3+.

CONCLUSION

Transvaginal ultrasound examination contributes to both prenatal management and the prediction of surgical outcomes in patients with a history of previous cesarean delivery with and without ultrasound signs suggestive of placenta accreta spectrum. Transvaginal ultrasound examination of the lower uterine segment and cervix should be included in clinical protocols for the preoperative evaluation of patients at risk of complex cesarean delivery.

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.

A risk factor profile for placenta accreta spectrum in pregnancies conceived with assisted reproductive technology

Objective

To identify independent risk factors for placenta accreta spectrum among pregnancies conceived with assisted reproductive technology.

Design

Retrospective cohort study.

Setting

Tertiary hospital.

Patients

Individuals who conceived with assisted reproductive technology and reached 20 weeks' gestation or later from 2011 to 2017.

Interventions

Patient and cycle data was abstracted from hospital records and supplemented with state-level data. Poisson regression was used for multivariate analyses and reported as adjusted relative risks (aRR).

Main Outcome Measures

Clinical or histologic placenta accreta spectrum.

Results

Of 1,975 qualifying pregnancies, 44 (2.3%) met criteria for accreta spectrum at delivery. In the multivariate model, significant risk factors included low-lying placenta at delivery (aRR, 15.44; 95% CI 7.76-30.72), uterine factor infertility or prior uterine surgery (aRR, 4.68; 95% CI, 2.72-8.05), initial low-lying placentation that resolved (aRR, 3.83; 95% CI, 1.90-7.73), and use of frozen embryos (aRR, 3.02; 95% CI, 1.66-5.48). When the fresh vs frozen variable was replaced with controlled ovarian hyperstimulation, the final model did not change (aRR, 2.40 for unstimulated cycles, 95% CI, 1.32-4.38). With frozen transfers, the accreta rate was 16% when the endometrial thickness was < 6mm vs 3.8% with thicker endometrium (P=.02).

Conclusions

Among pregnancies conceived with assisted reproductive technology, accreta spectrum is associated with low placental implantation (even when resolved), uterine factor infertility and prior uterine surgery, and the use of frozen embryo transfer or unstimulated cycles.

Implementation and outcomes of a uterine artery embolization and tranexamic acid protocol for placenta accreta spectrum

BACKGROUND

Placenta accreta spectrum disorders are a continuum of placental pathologies with significant maternal morbidity and mortality. Morbidity is related to the overall degree of placental adherence, and thus patients with placenta increta or percreta represent a high-risk category of patients. Hemorrhage and transfusion of blood products represent 90% of placenta accreta spectrum morbidity. Both tranexamic acid and uterine artery embolization independently decrease obstetrical hemorrhage.

OBJECTIVE

This study aimed to provide an evidence-based intraoperative protocol for placenta accreta spectrum management.

STUDY DESIGN

This study was a pre- and postimplementation analysis of concomitant uterine artery embolization and tranexamic acid in cases of patients with antenatally suspected placenta increta and percreta over a 5-year period (2018-2022). For comparison, a 5-year (2013-2017) preimplementation group was used to assess the impact of the uterine artery embolization and tranexamic acid protocol for placenta accreta spectrum. Patient demographics and clinically relevant outcomes were obtained from electronic medical records.

RESULTS

A total of 126 cases were managed by the placenta accreta spectrum team, of which 66 had suspected placenta increta/percreta over the 10-year time period. Two patients were excluded from the postimplementation cohort because they did not undergo both interventions. Thus, 30 (30/64; 47%) were treated after implementation of the uterine artery embolization and tranexamic acid protocol for placenta accreta spectrum, and 34 (34/64; 53%) preimplementation patients did not undergo uterine artery embolization or tranexamic acid infusion. With the uterine artery embolization and tranexamic acid protocol, operative times were longer (416 vs 187 minutes; P<.01), and patients were more likely to receive general anesthesia (80% vs 47%; P<.01). However, blood loss was reduced by 33% (2000 vs 3000 cc; P=.03), overall blood transfusion rates decreased by 51% (odds ratio, 0.05 [95% confidence interval, 0.001-0.20]; P<.01), and massive blood transfusion (>10 units transfused) was reduced 5-fold (odds ratio, 0.17 [95% confidence interval, 0.02-0.17]; P=.02). Postoperative complication rates remained unchanged (4 vs 10 events; P=.14). Neonatal outcomes were equivalent.

CONCLUSION

The uterine artery embolization and tranexamic acid protocol for placenta accreta spectrum is an effective approach to the standardization of complex placenta accreta spectrum cases that results in optimal perioperative outcomes and reduced maternal morbidity.

Impact of purse-string uterine suture on scar healing after a cesarean delivery: a randomized controlled trial

BACKGROUND

Uterine closure technique can affect scar healing, potentially resulting in unfavorable gynecologic and life-threatening obstetrical outcomes. Double-layer continuous unlocked suture has been demonstrated to promote optimal residual myometrial thickness. Recently, the purse-string uterine suture technique has emerged as a viable method to enhance the healing of scars. However, the current lack of randomized trials assessing the relevance of this technique warrants further investigation.

OBJECTIVE

This study aimed to evaluate the impact of purse-string uterine sutures on scar healing after cesarean delivery when compared with double-layer continuous unlocked suture.

STUDY DESIGN

This was a randomized controlled trial; 126 patients with singleton pregnancies undergoing primary cesarean delivery were enrolled in 2 groups. The primary outcome was the mean residual myometrial thickness measured by saline infusion sonography 6 months after surgery by 2 sonographers blinded to uterine closure techniques. Operative time, calculated blood loss, total number of needed threads, and perioperative scar width were used for the perioperative analysis. Healing ratio and cesarean scar defect measurements were used for the 6-month analysis.

RESULTS

There was no significant difference in terms of residual myometrial thickness (9.38±2.3 vs 8.4±3.9 mm; P=.187), blood loss (540 [146-982] vs 495 [241-903] mL; P=.815), or operative time (6.2 [5.2-7] vs 6 [5.3-7] minutes; P=.977). Achievement of purse-string uterine suture required significantly fewer threads (1 [1-1] vs 2 [1-2]; P<.001) and fewer hemostatic complementary sutures (1 [1-1] vs 1 [1-2]; P=.013). Scar width was significantly lower with purse-string uterine sutures (50 [40.5-50.5] vs 70 [60-70.5] mm; P<.0001). Purse-string uterine sutures allowed a higher healing ratio (1 [0.9-1] vs 0.84 [0.59-1]; P=.003) and significantly fewer cesarean scar defects (12% vs 35%; P=.018) compared with double-layer continuous unlocked suture.

CONCLUSION

Despite resulting in no difference in residual myometrial thickness, purse-string uterine closure seems to be associated with better uterine scar healing on the basis of a higher healing ratio, and a lower rate of cesarean scar defects compared with double-layer continuous unlocked suture.

Reproductive and Obstetric Outcomes Following a Natural Cycle vs. Artificial Endometrial Preparation for Frozen-Thawed Embryo Transfer: A Retrospective Cohort Study

Background: The proportion of frozen embryo transfer cycles has consistently grown in recent decades. Some adverse obstetric outcomes after frozen embryo transfer could possibly be explained by different approaches in endometrial preparation. The aim of the present study was to investigate reproductive and obstetric outcomes after frozen embryo transfer, comparing different endometrial preparation strategies. Methods: This retrospective study included 317 frozen embryo transfer cycles, of which 239 had a natural or modified natural cycle and 78 underwent artificial endometrial preparation. After excluding late abortion and twin pregnancies, the outcomes of 103 pregnancies were analyzed, 75 of which were achieved after a natural cycle/modified natural cycle, and 28 were achieved after an artificial cycle. Results: The overall clinical pregnancy rate/embryo transfer was 39.7%, the miscarriage rate was 10.1%, and the live birth rate/embryo transfer was 32.8%, without significant differences in reproductive outcomes between natural/modified cycle and artificial cycle groups. The risks of pregnancy-induced hypertension and abnormal placental insertion were significantly increased in pregnancies achieved after the artificial preparation of the endometrium (p = 0.0327 and =0.0191, respectively). Conclusions: Our study encourages the use of a natural cycle or modified natural cycle for endometrial preparation for frozen embryo transfer in order to ensure the presence of a corpus luteum able to orchestrate maternal adaptation to pregnancy.

Surgical evacuation of cesarean scar ectopic pregnancies

Cesarean scar ectopic pregnancy is associated with significant maternal morbidity, including severe hemorrhage, need for the blood transfusion and hysterectomy. Early diagnosis is therefore key in ensuring timely management, with consensus being that treatment before 9 weeks of gestation leads to reduced morbidity. There is no universally adopted management protocol for cesarean scar ectopic pregnancy, but surgical management generally has a higher success rate than medical management. The primary surgical treatment modalities are suction evacuation versus resection of the pregnancy via multiple routes. Adjuncts that have been shown to successfully minimize bleeding with surgical management include cervical cerclage, balloon catheter, and uterine artery embolization. However, there remains a lack of high-quality evidence regarding what is the best surgical treatment option for cesarean scar ectopic pregnancy, and therefore it is essential that clinicians provide tailored management to patients considering the presenting symptoms and local expertise with various surgical techniques.

Definition and diagnosis of cesarean scar ectopic pregnancies

Cesarean scar ectopic pregnancy is a rare type of ectopic pregnancy, where the pregnancy implants into a myometrial defect caused by a cesarean scar. Its incidence is predicted to increase, given the global increase in cesarean deliveries. As most cesarean scar ectopic pregnancies present as failing pregnancies or patients choose termination of pregnancy, there are limited data on their natural history. However, early first trimester diagnosis is essential, given the associated significant maternal morbidity. Transvaginal sonography is generally considered to be the optimal method for diagnosing cesarean scar ectopic pregnancy. There is no evidence that MRI adds to the diagnostic accuracy, and it is therefore not recommended for routine evaluation of cesarean scar ectopic pregnancy. There is no agreed reference standard for the diagnosis of cesarean scar ectopic pregnancy; therefore, the validity of several proposed sonographic diagnostic criteria reported by different authors remains unknown. There are also various suggested classification systems for cesarean scar ectopic pregnancy, which divide them in differet types. However, the proposals are very heterogeneous, and superiority of one classification system over another is yet to be established.

Global variation and outcomes of expectant management of CSP

The incidence of Cesarean scar pregnancies (CSPs) is rising globally. Ultrasound criteria for the diagnosis of CSPs have been described by the International Society of Ultrasound in obstetrics and gynecology and appear to be well used in various centers around the world. There is no guidance on best practices for expectant management of CSP, and there is considerable variation in how this is offered globally. Many studies have reported significant maternal morbidity in cases of CSP with fetal cardiac activity managed expectantly, largely relating to hemorrhage and cesarean hysterectomy from placenta accreta spectrum. However, high live birth rates are also reported. Literature describing the diagnosis and expectant management of CSP in low-resource settings is lacking. Expectant management in selected cases where no fetal cardiac activity is present is a reasonable option and can be associated with good maternal outcomes. Standardization in reporting different types of CSPs and correlating these with pregnancy outcomes will be an important next step in developing guidance for expectant management of this high-risk pregnancy with a high burden of complications.

Animal models of the placenta accreta spectrum: current status and further perspectives

Placenta accreta spectrum disorder (PAS) is a kind of disease of placentation defined as abnormal trophoblast invasion of part or all of the placenta into the myometrium, even penetrating the uterus. Decidual deficiency, abnormal vascular remodeling in the maternal-fetal interface, and excessive invasion by extravillous trophoblast (EVT) cells contribute to its onset. However, the mechanisms and signaling pathways underlying such phenotypes are not fully understood, partly due to the lack of suitable experimental animal models. Appropriate animal models will facilitate the comprehensive and systematic elucidation of the pathogenesis of PAS. Due to the remarkably similar functional placental villous units and hemochorial placentation to humans, the current animal models of PAS are based on mice. There are various mouse models induced by uterine surgery to simulate different phenotypes of PAS, such as excessive invasion of EVT or immune disturbance at the maternal-fetal interface, which could define the pathological mechanism of PAS from the perspective of the "soil." Additionally, genetically modified mouse models could be used to study PAS, which is helpful to exploring the pathogenesis of PAS from the perspectives of both "soil" and "seed," respectively. This review details early placental development in mice, with a focus on the approaches of PAS modeling. Additionally, the strengths, limitations and the applicability of each strategy and further perspectives are summarized to provide the theoretical foundation for researchers to select appropriate animal models for various research purposes. This will help better determine the pathogenesis of PAS and even promote possible therapy.

Cesarean Scar Pregnancy: Current Understanding and Treatment Including Role of Minimally Invasive Surgical Techniques

The incidence of cesarean scar pregnancy (CSP) is increasing reflecting the global increase in cesarean section (CS) rate which has almost doubled since 2000. CSP differs from other types of ectopic pregnancy in its ability to progress while still carrying a significant risk of maternal morbidity. Little is known about precise etiology or natural history although current interest in the pathology of placenta accretes spectrum disorders might be enlightening. Early detection and treatment of CSP are challenging. Once diagnosed, the recommendation is to offer early termination of pregnancy because of the potential risks of continuing the pregnancy. However, as the likelihood of future pregnancy complications for any CSP varies depending on its individual characteristics, this might not always be necessary nor might it be the patient's preferred choice if she is asymptomatic, hemodynamically stable, and wants a baby. The literature supports an interventional rather than a medical approach but the safest and most efficient clinical approach to CSP in terms of treatment modality and service delivery has yet to be determined. This review aims to provide an overview of CSP etiology, natural history, and clinical implications. Treatment options and methods of CSP repair are discussed. We describe our experience in a large tertiary center in Singapore with around 16 cases/year where most treatment modalities are available as well as an "accreta service" for continuing pregnancies. We present a simple algorithm for approach to management including a method of triaging for those CSPs suitable for minimally invasive surgery.

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.

Spatial multiomics map of trophoblast development in early pregnancy

The relationship between the human placenta-the extraembryonic organ made by the fetus, and the decidua-the mucosal layer of the uterus, is essential to nurture and protect the fetus during pregnancy. Extravillous trophoblast cells (EVTs) derived from placental villi infiltrate the decidua, transforming the maternal arteries into high-conductance vessels1. Defects in trophoblast invasion and arterial transformation established during early pregnancy underlie common pregnancy disorders such as pre-eclampsia2. Here we have generated a spatially resolved multiomics single-cell atlas of the entire human maternal-fetal interface including the myometrium, which enables us to resolve the full trajectory of trophoblast differentiation. We have used this cellular map to infer the possible transcription factors mediating EVT invasion and show that they are preserved in in vitro models of EVT differentiation from primary trophoblast organoids3,4 and trophoblast stem cells5. We define the transcriptomes of the final cell states of trophoblast invasion: placental bed giant cells (fused multinucleated EVTs) and endovascular EVTs (which form plugs inside the maternal arteries). We predict the cell-cell communication events contributing to trophoblast invasion and placental bed giant cell formation, and model the dual role of interstitial EVTs and endovascular EVTs in mediating arterial transformation during early pregnancy. Together, our data provide a comprehensive analysis of postimplantation trophoblast differentiation that can be used to inform the design of experimental models of the human placenta in early pregnancy.

Identification of altered miRNAs and their targets in placenta accreta

Placenta accreta spectrum (PAS) is one of the major causes of maternal morbidity and mortality worldwide with increasing incidence. PAS refers to a group of pathological conditions ranging from the abnormal attachment of the placenta to the uterus wall to its perforation and, in extreme cases, invasion into surrounding organs. Among them, placenta accreta is characterized by a direct adhesion of the villi to the myometrium without invasion and remains the most common diagnosis of PAS. Here, we identify the potential regulatory miRNA and target networks contributing to placenta accreta development. Using small RNA-Seq followed by RT-PCR confirmation, altered miRNA expression, including that of members of placenta-specific miRNA clusters (e.g., C19MC and C14MC), was identified in placenta accreta samples compared to normal placental tissues. In situ hybridization (ISH) revealed expression of altered miRNAs mostly in trophoblast but also in endothelial cells and this profile was similar among all evaluated degrees of PAS. Kyoto encyclopedia of genes and genomes (KEGG) analyses showed enriched pathways dysregulated in PAS associated with cell cycle regulation, inflammation, and invasion. mRNAs of genes associated with cell cycle and inflammation were downregulated in PAS. At the protein level, NF-κB was upregulated while PTEN was downregulated in placenta accreta tissue. The identified miRNAs and their targets are associated with signaling pathways relevant to controlling trophoblast function. Therefore, this study provides miRNA:mRNA associations that could be useful for understanding PAS onset and progression.