Placenta creta and placenta praevia creta

Evaluation of fetal growth and birth weight in pregnancies with placenta previa with and without placenta accreta spectrum

OBJECTIVES

We evaluated fetal growth and birthweight in pregnancies with placenta previa with and without placenta accreta spectrum (PAS).

METHODS

We retrospectively studied pregnant patients with placenta previa with or without PAS diagnosed at 20-37 weeks' gestation. Estimated fetal weight (EFW) percentile and fetal growth rate were calculated based on ultrasound at two timepoints: 20-24 and 30-34-weeks' gestation. Fetuses were small (SGA) or large for gestational age (LGA) when EFW or abdominal circumference was <10th or >90th percentile for gestational age, respectively. Fetal growth rate was estimated by subtracting EFW percentiles from the two ultrasounds. Birthweight in grams and percentiles were estimated via Anderson and INTERGROWTH-21 standards adjusted for neonatal sex. EFW percentiles, fetal growth rate, birth weight and birthweight percentiles were compared between patients with placenta previa with and without PAS.

RESULTS

We studied 171 patients with and 146 patients without PAS. SGA rates did not differ between groups on first (PAS n=3, no-PAS n=3, p=0.8) or second ultrasound (PAS n=10, no-PAS n=8, p=0.8). LGA rates were similar between groups on first (PAS n=11, no-PAS n=9, p=0.8) and second ultrasound (PAS n=20, no-PAS n=12, p=0.6). The growth rate was higher in fetuses with PAS than placenta previa (1.22 ± 22.3 vs. -4.1 ± 18.1, p=0.07), but not significantly. The birthweight percentile was higher in the PAS than the placenta previa group (74 vs. 67, p=0.01). On multi-linear regression, birthweight percentile remained higher in the PAS group, but not significantly.

CONCLUSIONS

Placenta previa with or without PAS is not associated with SGA, LGA or lower birthweight.

Uterine injury during diestrus leads to placental and embryonic defects in future pregnancies in mice†

Uterine injury from procedures such as Cesarean sections (C-sections) often have severe consequences on subsequent pregnancy outcomes, leading to disorders such as placenta previa, placenta accreta, and infertility. With rates of C-section at ~30% of deliveries in the USA and projected to continue to climb, a deeper understanding of the mechanisms by which these pregnancy disorders arise and opportunities for intervention are needed. Here we describe a rodent model of uterine injury on subsequent in utero outcomes. We observed three distinct phenotypes: increased rates of resorption and death, embryo spacing defects, and placenta accreta-like features of reduced decidua and expansion of invasive trophoblasts. We show that the appearance of embryo spacing defects depends entirely on the phase of estrous cycle at the time of injury. Using RNA-seq, we identified perturbations in the expression of components of the COX/prostaglandin pathway after recovery from injury, a pathway that has previously been demonstrated to play an important role in embryo spacing. Therefore, we demonstrate that uterine damage in this mouse model causes morphological and molecular changes that ultimately lead to placental and embryonic developmental defects.

Pathologic maternal and neonatal outcomes associated with programmed embryo transfer: potential etiologies and strategies for prevention

PURPOSE

In the first of two companion papers, we comprehensively reviewed the recent evidence in the primary literature, which addressed the increased prevalence of hypertensive disorders of pregnancy, late-onset or term preeclampsia, fetal overgrowth, postterm birth, and placenta accreta in women conceiving by in vitro fertilization. The preponderance of evidence implicated frozen embryo transfer cycles and, specifically, those employing programmed endometrial preparations, in the higher risk for these adverse maternal and neonatal pregnancy outcomes. Based upon this critical appraisal of the primary literature, we formulate potential etiologies and suggest strategies for prevention in the second article.

METHODS

Comprehensive review of primary literature.

RESULTS

Presupposing significant overlap of these apparently diverse pathological pregnancy outcomes within subjects who conceive by programmed autologous FET cycles, shared etiologies may be at play. One plausible but clearly provocative explanation is that aberrant decidualization arising from suboptimal endometrial preparation causes greater than normal trophoblast invasion and myometrial spiral artery remodeling. Thus, overly robust placentation produces larger placentas and fetuses that, in turn, lead to overcrowding of villi within the confines of the uterine cavity which encroach upon intervillous spaces precipitating placental ischemia, oxidative and syncytiotrophoblast stress, and, ultimately, late-onset or term preeclampsia. The absence of circulating corpus luteal factors like relaxin in most programmed cycles might further compromise decidualization and exacerbate the maternal endothelial response to deleterious circulating placental products like soluble fms-like tyrosine kinase-1 that mediate disease manifestations. An alternative, but not mutually exclusive, determinant might be a thinner endometrium frequently associated with programmed endometrial preparations, which could conspire with dysregulated decidualization to elicit greater than normal trophoblast invasion and myometrial spiral artery remodeling. In extreme cases, placenta accreta could conceivably arise. Though lower uterine artery resistance and pulsatility indices observed during early pregnancy in programmed embryo transfer cycles are consistent with this initiating event, quantitative analyses of trophoblast invasion and myometrial spiral artery remodeling required to validate the hypothesis have not yet been conducted.

CONCLUSIONS

Endometrial preparation that is not optimal, absent circulating corpus luteal factors, or a combination thereof are attractive etiologies; however, the requisite investigations to prove them have yet to be undertaken. Presuming that in ongoing RCTs, some or all adverse pregnancy outcomes associated with programmed autologous FET are circumvented or mitigated by employing natural or stimulated cycles instead, then for women who can conceive using these regimens, they would be preferable. For the 15% or so of women who require programmed FET, additional research as suggested in this review is needed to elucidate the responsible mechanisms and develop preventative strategies.

Risk factors for placenta accreta spectrum disorders in women with any prior cesarean and a placenta previa or low lying: a prospective population-based study

This study aimed to identify the risk factors for placenta accreta spectrum (PAS) in women who had at least one previous cesarean delivery and a placenta previa or low-lying. The PACCRETA prospective population-based study took place in 12 regional perinatal networks from 2013 through 2015. All women with one or more prior cesareans and a placenta previa or low lying were included. Placenta accreta spectrum (PAS) was diagnosed at delivery according to standardized clinical and histological criteria. Of the 520,114 deliveries, 396 fulfilled inclusion criteria; 108 were classified with PAS at delivery. Combining the number of prior cesareans and the placental location yielded a rate ranging from 5% for one prior cesarean combined with a posterior low-lying placenta to 63% for three or more prior cesareans combined with placenta previa. The factors independently associated with PAS disorders were BMI ≥ 30, previous uterine surgery, previous postpartum hemorrhage, a higher number of prior cesareans, and a placenta previa. Finally, in this high-risk population, the rate of PAS disorders varies greatly, not only with the number of prior cesareans but also with the exact placental location and some of the women's individual characteristics. Risk stratification is thus possible in this population.

Shallow Placentation: A Distinct Category of Placental Lesions

OBJECTIVE

Shallow placental implantation (SPI) features placental maldistribution of extravillous trophoblasts and includes excessive amount of extravillous trophoblasts, chorionic microcysts in the membranes and chorionic disc, and decidual clusters of multinucleate trophoblasts. The histological lesions were previously and individually reported in association with various clinical and placental abnormalities. This retrospective statistical analysis of a large placental database from high-risk pregnancy statistically compares placentas with and without a composite group of features of SPI.

STUDY DESIGN

Twenty-four independent abnormal clinical and 44 other than SPI placental phenotypes were compared between 4,930 placentas without (group 1) and 1,283 placentas with one or more histological features of SPI (composite SPI group; group 2). Placentas were received for pathology examination at a discretion of obstetricians. Placental lesion terminology was consistent with the Amsterdam criteria, with addition of other lesions described more recently.

RESULTS

Cases of group 2 featured statistically and significantly (p < 0.001after Bonferroni's correction) more common than group 1 on the following measures: gestational hypertension, preeclampsia, oligohydramnios, polyhydramnios, abnormal Dopplers, induction of labor, cesarean section, perinatal mortality, fetal growth restriction, stay in neonatal intensive care unit (NICU), congenital malformation, deep meconium penetration, intravillous hemorrhage, villous infarction, membrane laminar necrosis, fetal blood erythroblastosis, decidual arteriopathy (hypertrophic and atherosis), chronic hypoxic injury (uterine and postuterine), intervillous thrombus, segmental and global fetal vascular malperfusion, various umbilical cord abnormalities, and basal plate myometrial fibers.

CONCLUSION

SPI placentas were statistically and significantly associated with 48% abnormal independent clinical and 51% independent abnormal placental phenotypes such as acute and chronic hypoxic lesions, fetal vascular malperfusion, umbilical cord abnormalities, and basal plate myometrial fibers among others. Therefore, SPI should be regarded as a category of placental lesions related to maternal vascular malperfusion and the "Great Obstetrical Syndromes."

KEY POINTS

· SPI reflects abnormal distribution of extravillous trophoblasts.. · SPI features abnormal clinical and placental phenotypes.. · SPI portends increased risk of complicated perinatal outcome..

Placenta Accreta Spectrum

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

Uterine artery embolization for postpartum hemorrhage with placenta accreta spectrum

BACKGROUND

The reported success rate of uterine artery embolization (UAE) for postpartum hemorrhage (PPH) differs by the cause of bleeding; in some reports, UAE shows less successful results in patients with placenta accreta spectrum (PAS).

PURPOSE

To evaluate the outcome of UAE for treating PPH associated with PAS.

MATERIAL AND METHODS

From September 2011 to September 2021, 227 patients (mean age = 34.67±4.06 years; age range = 19-47 years) underwent UAE for managing intractable PPH. Patients were divided into two groups: those with PAS (n = 46) and those without PAS (n = 181). Delivery details, embolization details, and procedure-related outcomes were compared between the two groups. P values <0.05 were considered statistically significant.

RESULTS

The technical success rate was 96.9% (n = 222) and the clinical success rate was 93.8% (n = 215). There were no significant differences in outcome of UAE between the two patient groups. The technical success rate was 95.7% (n = 44) in patients with PAS and 98.3% (n = 178) in patients without PAS (P = 0.267). The clinical success rate was 91.3% (n = 42) in patients with PAS and 95.6% (n = 173) in patients without PAS (P = 0.269). There were 24 cases of immediate complications, including pelvic pain (n = 20), urticaria (n = 3), and puncture site hematoma (n = 1). No major complication was reported.

CONCLUSION

UAE is a safe and effective method to control intractable PPH for patients with or without PAS.

Life After Amsterdam: Placental Pathology Consensus Recommendations and Beyond

The Amsterdam Placental Workshop Group Consensus Statement on Sampling and Definitions of Placental Lesions has become widely accepted and is increasingly used as the universal language to describe the most common pathologic lesions found in the placenta. This review summarizes the most salient aspects of this seminal publication and the subsequent emerging literature based on Amsterdam definitions and criteria, with emphasis on publications relating to diagnosis, grading, and staging of placental pathologic conditions. We also provide an overview of the recent expert recommendations on the pathologic grading of placenta accreta spectrum, with insights on their clinical context. Finally, we discuss the emerging entity of SARS-CoV2 placentitis.

Searching for placenta percreta: a prospective cohort and systematic review of case reports

BACKGROUND

Placenta percreta is described as the most severe grade of placenta accreta spectrum and accounts for a quarter of all cases of placenta accreta spectrum reported in the literature.

OBJECTIVE

We investigated the hypothesis that placenta percreta, which has been described clinically as placental tissue invading through the full thickness of the uterus, is a heterogeneous category with most cases owing to primary or secondary uterine abnormality rather than an abnormally invasive form of placentation.

STUDY DESIGN

We have evaluated the agreement between the intraoperative findings using the International Federation of Gynecology and Obstetrics classification with the postoperative histopathology diagnosis in a prospective cohort of 101 consecutive singleton pregnancies presenting with a low-lying placenta or placenta previa, a history of at least 1 prior cesarean delivery and ultrasound signs suggestive of placenta accreta spectrum. Furthermore, a systematic literature review of case reports of placenta percreta, which included histopathologic findings and gross images, was performed.

RESULTS

Samples for histologic examination were available in 80 of 101 cases of the cohort, which were managed by hysterectomy or partial myometrial resection. Microscopic examination showed evidence of placenta accreta spectrum in 65 cases (creta, 9; increta, 56). Of 101 cases included in the cohort, 44 (43.5%) and 54 (53.5%) were graded as percreta by observer A and observer B, respectively. There was a moderate agreement between observers. Of note, 11 of 36 cases that showed no evidence of abnormal placental attachment at delivery and/or microscopic examination were classified as percreta by both observers. The systematic literature review identified 41 case reports of placenta percreta with microscopic images and presenting symptomatology, suggesting that most cases were the consequence of a uterine rupture. The microscopic descriptions were heterogeneous, and all descriptions demonstrated histology of placenta creta rather than percreta.

CONCLUSION

Our study supported the concept that placenta accreta is not an invasive disorder of placentation but the consequence of postoperative surgical remodeling or a preexisting uterine pathology and found no histologic evidence supporting the existence of a condition where the villous tissue penetrates the entire uterine wall, including the serosa and beyond.

Monoexponential, biexponential and diffusion kurtosis MR imaging models: quantitative biomarkers in the diagnosis of placenta accreta spectrum disorders

BACKGROUND

To investigate the diagnostic value of monoexponential, biexponential, and diffusion kurtosis MR imaging (MRI) in differentiating placenta accreta spectrum (PAS) disorders.

METHODS

A total of 65 patients with PAS disorders and 27 patients with normal placentas undergoing conventional DWI, IVIM, and DKI were retrospectively reviewed. The mean, minimum, and maximum parameters including the apparent diffusion coefficient (ADC) and exponential ADC (eADC) from standard DWI, diffusion kurtosis (MK), and mean diffusion coefficient (MD) from DKI and pure diffusion coefficient (D), pseudo-diffusion coefficient (D*), and perfusion fraction (f) from IVIM were measured from the volumetric analysis and compared between patients with PAS disorders and patients with normal placentas. Univariate and multivariated logistic regression analyses were used to evaluate the value of the above parameters for differentiating PAS disorders. Receiver operating characteristics (ROC) curve analyses were used to evaluate the diagnostic efficiency of different diffusion parameters for predicting PAS disorders.

RESULTS

Multivariate analysis demonstrated that only D mean and D max differed significantly among all the studied parameters for differentiating PAS disorders when comparisons between accreta lesions in patients with PAS (AP) and whole placentas in patients with normal placentas (WP-normal) were performed (all p < 0.05). For discriminating PAS disorders, a combined use of these two parameters yielded an AUC of 0.93 with sensitivity, specificity, and accuracy of 83.08, 88.89, and 83.70%, respectively.

CONCLUSION

The diagnostic performance of the parameters from accreta lesions was better than that of the whole placenta. D mean and D max were associated with PAS disorders.

New insights into the etiopathology of placenta accreta spectrum

Placenta accreta has been described as a spectrum of abnormal attachment of villous tissue to the uterine wall, ranging from superficial attachment to the inner myometrium without interposing decidua to transmural invasion through the entire uterine wall and beyond. These descriptions have prevailed for more than 50 years and form the basis for the diagnosis and grading of accreta placentation. Accreta placentation is essentially the consequence of uterine remodeling after surgery, primarily after cesarean delivery. Large cesarean scar defects in the lower uterine segment are associated with failure of normal decidualization and loss of the subdecidual myometrium. These changes allow the placental anchoring villi to implant, and extravillous trophoblast cells to migrate, close to the serosal surface of the uterus. These microscopic features are central to the misconception that the accreta placental villous tissue is excessively invasive and have led to much confusion and heterogeneity in clinical data. Progressive recruitment of large arteries in the uterine wall, that is, helicine, arcuate, and/or radial arteries, results in high-velocity maternal blood entering the intervillous space from the first trimester of pregnancy and subsequent formation of placental lacunae. Recently, guided sampling of accreta areas at delivery has enabled accurate correlation of prenatal imaging data with intraoperative features and histopathologic findings. In more than 70% of samples, there were thick fibrinoid depositions between the tip of most anchoring villi and the underlying uterine wall and around all deeply implanted villi. The distortion of the uteroplacental interface by these dense depositions and the loss of the normal plane of separation are the main factors leading to abnormal placental attachment. These data challenged the classical concept that placenta accreta is simply owing to villous tissue sitting atop the superficial myometrium without interposed decidua. Moreover, there is no evidence in accreta placentation that the extravillous trophoblast is abnormally invasive or that villous tissue can cross the uterine serosa into the pelvis. It is the size of the scar defect, the amount of placental tissue developing inside the scar, and the residual myometrial thickness in the scar area that determine the distance between the placental basal plate and the uterine serosa and thus the risk of accreta placentation.

Failure of placental detachment in accreta placentation is associated with excessive fibrinoid deposition at the utero-placental interface

BACKGROUND

The main histopathologic diagnostic criteria for the diagnosis of placenta accreta for more than 80 years has been the finding of a direct attachment of the villous tissue to the superficial myometrium or adjacent to myometrial fibers without interposing decidua. There have been very few detailed histopathologic studies in pregnancies complicated by placenta accreta spectrum disorders and our understanding of the pathophysiology of the condition remains limited.

OBJECTIVE

To prospectively evaluate the microscopic changes used in grading and to identify changes that might explain the abnormal placental tissue attachment.

STUDY DESIGN

A total of 40 consecutive cesarean delivery hysterectomy specimens for placenta previa accreta at 32 to 37 weeks of gestation with at least 1 histologic slide showing deeply implanted villi were analyzed. Prenatal ultrasound examination included placental location, myometrial thickness, subplacental vascularity and lacunae. Macroscopic changes of the lower segment were recorded during surgery and areas of abnormal placental adherence were sampled for histology. In addition, 7 hysterectomy specimens with placenta in-situ from the Boyd Collection at 20.5 to 32.5 weeks were used as controls.

RESULTS

All 40 patients had a history of at least 2 previous cesarean deliveries and presented with a mainly anterior placenta previa. Of note, 37 (92.5%) cases presented with increased subplacental vascularity, 31 (77.5%) cases with myometrial thinning and all with lacunae. Furthermore, 20 (50%) cases presented with subplacental hypervascularity, lacunae score of >3, and lacunae feeder vessels. Intraoperative findings included anterior lower segment wall increased vascularization in 36 (90.0%) cases and extended area of dehiscence in 18 (45.0%) cases. Immediate gross examination of hysterectomy specimens showed an abnormally attached areas involving up to 30% of the basal plate, starting at <2 cm from the dehiscence area in all cases. Histologic examination found deeply implanted villi in 86 (53.8%) samples with only 17 (10.6%) samples presenting with villous tissue reaching at least half the uterine wall thickness. There were no villi crossing the entire thickness of the uterine wall. There was microscopic evidence of myometrial scarification in all cases. Dense fibrinoid deposits, 0.5 to 2 mm thick, were found at the utero-placental interface in 119 (74.4%) of the 160 samples between the anchoring villi and the underlying uterine wall at the accreta areas and around all deeply implanted villi. In the control group, the Nitabuch stria and basal plate became discontinuous with advancing gestation and there was no evidence of fibrinoid deposition at these sites.

CONCLUSION

Samples from accreta areas at delivery present with a thick fibrinoid deposition at the utero-placental interface on microscopic examination independently of deeply implanted villous tissue in the sample. These changes are associated with distortion of the Nitabuch membrane and might explain the loss of parts of the physiological site of detachment of the placenta from the uterine wall in placenta accreta spectrum. These findings indicate that accreta placentation is more than direct attachment of the villous tissue to the superficial myometrium and support the concept that accreta villous tissue is not truly invasive.

Uterine natural killer cell biology and role in early pregnancy establishment and outcomes

Objective

While immune cells were originally thought to only play a role in maternal tolerance of the semiallogenic fetus, an active role in pregnancy establishment is becoming increasingly apparent. Uterine natural killer (uNK) cells are of specific interest because of their cyclic increase in number during the window of implantation. As a distinct entity from their peripheral blood counterparts, understanding the biology and function of uNK cells will provide the framework for understanding their role in early pregnancy establishment and adverse pregnancy outcomes.

Evidence Review

This review discusses unique uNK cell characteristics and presents clinical implications resulting from their dysfunction. We also systematically present existing knowledge about uNK cell function in three processes critical for successful human embryo implantation and placentation: stromal cell decidualization, spiral artery remodeling, and extravillous trophoblast invasion. Finally, we review the features of uNK cells that could help guide future investigations.

Results

It is clear the uNK cells are intimately involved in multiple facets of early pregnancy. This is accomplished directly, through the secretion of factors that regulate stromal cells and trophoblast function; and indirectly, via interaction with other maternal cell types present at the maternal-fetal interface. Current work also suggests that uNK cells are a heterogenous population, with subsets that potentially accomplish different functions.

Conclusion

Establishment of pregnancy through successful embryo implantation and placentation requires crosstalk between multiple maternal cell types and invading fetal trophoblast cells. Defects in this process have been associated with multiple adverse perinatal outcomes including hypertensive disorders of pregnancy, placenta accreta, and recurrent miscarriage though the mechanism underlying development of these defects remain unclear. Abnormalities in NK cell number and function which would disrupt physiological maternal-fetal crosstalk, could play a critical role in abnormal implantation and placentation. It is therefore imperative to dissect the unique physiological role of uNK cells in pregnancy and use this knowledge to inform clinical practice by determining how uNK cell dysfunction could lead to reproductive failure.

Pregnancy-Related Hysterectomy for Peripartum Hemorrhage: A Literature Narrative Review of the Diagnosis, Management, and Techniques

Postpartum hemorrhage is a life-threatening situation, in which hysterectomy can be performed to prevent maternal death. However, it is associated with high rates of maternal morbidity and mortality and permanent infertility. The incidence of pregnancy-related hysterectomy varies across countries, but its main indications are the following: uterine atony and placenta spectrum (PAS) disorders. PAS disorder prevalence is rising during the last years, mainly due to the increased number of cesarean sections. As a result, obstetricians should be aware of the difficulties of this emergent condition and improve its accurate antenatal diagnosis rates, as well as its modern management strategies. Of course, special skills are required during a pregnancy-related hysterectomy, so these patients should be referred to centers of excellence in antenatal care, where a multidisciplinary team approach is followed. This study is a narrative review of the literature of the last 5 years (PubMed, Cochrane) regarding postpartum hemorrhage to offer obstetricians up-to-date knowledge on this pregnancy-related life-threatening issue. However, there is a lack of available high-quality data, because most published papers are retrospective case series or observational cohorts.

PRG2 and AQPEP are misexpressed in fetal membranes in placenta previa and percreta†

The obstetrical conditions placenta accreta spectrum (PAS) and placenta previa are a significant source of pregnancy-associated morbidity and mortality, yet the specific molecular and cellular underpinnings of these conditions are not known. In this study, we identified misregulated gene expression patterns in tissues from placenta previa and percreta (the most extreme form of PAS) compared with control cases. By comparing this gene set with existing placental single-cell and bulk RNA-Seq datasets, we show that the upregulated genes predominantly mark extravillous trophoblasts. We performed immunofluorescence on several candidate molecules and found that PRG2 and AQPEP protein levels are upregulated in both the fetal membranes and the placental disk in both conditions. While this increased AQPEP expression remains restricted to trophoblasts, PRG2 is mislocalized and is found throughout the fetal membranes. Using a larger patient cohort with a diverse set of gestationally aged-matched controls, we validated PRG2 as a marker for both previa and PAS and AQPEP as a marker for only previa in the fetal membranes. Our findings suggest that the extraembryonic tissues surrounding the conceptus, including both the fetal membranes and the placental disk, harbor a signature of previa and PAS that is characteristic of EVTs and that may reflect increased trophoblast invasiveness.

Clinical profiles of placenta accreta spectrum: the PACCRETA population-based study

OBJECTIVE

To describe and compare the characteristics of women with placenta accreta spectrum (PAS) and their pregnancy outcomes according to the presence of placenta praevia and a prior caesarean section.

DESIGN

Prospective population-based study.

SETTING

All 176 maternity hospitals of eight French regions.

POPULATION

Two hundred and forty-nine women with PAS, from a source population of 520 114 deliveries.

METHODS

Women with PAS were classified into two risk-profile groups, with or without the high-risk combination of placenta praevia (or an anterior low-lying placenta) and at least one prior caesarean. These two groups were described and compared.

MAIN OUTCOME MEASURES

Population-based incidence of PAS, characteristics of women, pregnancies, deliveries and pregnancy outcomes.

RESULTS

The PAS population-based incidence was 4.8/10 000 (95% CI 4.2-5.4/10 000). After exclusion of women lost to follow up from the analysis, the group with placenta praevia and a prior caesarean included 115 (48%) women and the group without this combination included 127 (52%). In the group with both factors, PAS was more often suspected antenatally (77% versus 17%; P < 0.001) and more often percreta (38% versus 5%; P < 0.001). This group also had more hysterectomies (53% versus 21%, P < 0.001) and higher rates of blood product transfusions, maternal complications, preterm births and neonatal intensive care unit admissions. Sensitivity analysis showed similar results after exclusion of women who delivered vaginally.

CONCLUSION

More than half the cases of PAS occurred in women without the combination of placenta praevia and a prior caesarean delivery, and these women had better maternal and neonatal outcomes. We cannot completely rule out that some of the women who delivered vaginally had placental retention rather than PAS; however, we found similar results among women who delivered by caesarean.

TWEETABLE ABSTRACT

Half the women with PAS do not have both placenta praevia and a prior caesarean delivery, and they have better maternal outcomes.

Classification and reporting guidelines for the pathology diagnosis of placenta accreta spectrum (PAS) disorders: recommendations from an expert panel

The terminology and diagnostic criteria presently used by pathologists to report invasive placentation is inconsistent and does not reflect current knowledge of the pathogenesis of the disease or the needs of the clinical care team. A consensus panel was convened to recommend terminology and reporting elements unified across the spectrum of PAS specimens (i.e., delivered placenta, total or partial hysterectomy with or without extrauterine tissues, curetting for retained products of conception). The proposed nomenclature under the umbrella diagnosis of placenta accreta spectrum (PAS) replaces the traditional categorical terminology (placenta accreta, increta, percreta) with a descriptive grading system that parallels the guidelines endorsed by the International Federation of Gynaecology and Obstetrics (FIGO). In addition, the nomenclature for hysterectomy specimens is separated from that for delivered placentas. The goal for each element in the system of nomenclature was to provide diagnostic criteria and guidelines for expected use in clinical practice.

Placenta Creta: A Spectrum of Lesions Associated with Shallow Placental Implantation

Background

On placental histology, placenta creta (PC) ranges from clinical placenta percreta through placenta increta and accreta (clinical and occult) to myometrial fibers with intervening decidua. This retrospective study aimed to investigate the clinicopathologic correlations of these lesions.

Methods

A total of 169 recent consecutive cases with PC (group 1) were compared with 1661 cases without PC examined during the same period (group 2). The frequencies of 25 independent clinical and 40 placental phenotypes were statistically compared between the groups using chi-square test or analysis of variance where appropriate.

Results

Group 1 placentas, as compared with group 2 placentas, were statistically significantly (p < 0.05) associated with caesarean sections (11.2% vs. 7.5%), antepartum hemorrhage (17.7% vs 11.6.%), gestational hypertension (11.2% vs 4.3%), preeclampsia (11.8% vs 2.6%), complicated third stage of labor (18.9% vs 6.4%), villous infarction (14.2% vs 8.9%), chronic hypoxic patterns of placental injury, particularly the uterine pattern (14.8%, vs 9.6%), massive perivillous fibrin deposition (9.5% vs 5.3%), chorionic disc chorionic microcysts (21.9% vs 15.9%), clusters of maternal floor multinucleate trophoblasts (27.8% vs 21.2%), excessive trophoblasts of chorionic disc (24.3% vs 17.3%), segmental fetal vascular malperfusion (27.8% vs 19.9%), and fetal vascular ectasia (26.2% vs 15.2%).

Conclusion

Because of the association of PC with gestational hypertensive diseases, acute and chronic placental hypoxic lesions, increased extravillous trophoblasts in the chorionic disc, chorionic microcysts, and maternal floor trophoblastic giant cells, PC should be regarded as a lesion of abnormal placental implantation and abnormal trophoblast invasion rather than decidual deficiency only.

Placenta Accreta Spectrum Disorders: Challenges, Risks, and Management Strategies

The worldwide incidence of placenta accreta spectrum (PAS) is rapidly increasing, following the trend of rising cesarean delivery. PAS is an heterogeneous condition associated with a high maternal morbidity and mortality rate, presenting unique challenges in its diagnosis and management. So far, the rarity of this condition, together with the absence of high quality evidence and the lack of a standardized approach in reporting PAS cases for the ultrasound, clinical, and pathologic diagnosis, represented the main challenges for a deep understanding of this condition. The study of the available management strategies of PAS has been hampered by the heterogeneity of the available epidemiological data on this condition. The aim of this review is to provide a critical view of the current available evidence on the screening, the diagnosis, and the management options for PAS disorders, with a special focus on the challenges we foresee for the near future.

Ultrasound-histopathologic features of the utero-placental interface in placenta accreta spectrum

INTRODUCTION

The objective of this study was to evaluate the relationship between utero-placental vascular changes on ultrasound imaging and histopathologic findings according to the grade of villous invasion in placenta accreta spectrum (PAS).

METHODS

The ultrasound features of 31 patients with singleton pregnancies diagnosed prenatally with low-lying/placenta previa accreta were compared with histopathology findings following caesarean hysterectomy (n = 25) or partial myometrial resection (n = 6). The number and degree of transformation of arteries within the superficial layer of myometrium were recorded. Cytokeratin 7 (CK7) immunohistochemistry was used to complement H&E analysis.

RESULTS

All 31 patients presented with loss of clear zone, myometrial thinning and placenta lacunae. Subplacental hypervascularity and lacunae feeder vessels were found in 25 and nine cases, respectively. Large recent intervillous thromboses were found in one case with adherent villi and 12 cases with invasive villi, and showed a significantly different distribution according to lacunae scores. Thick basal plate fibrinoid deposits were found in all the areas of abnormally adherent and invasive villous tissue There was no significant difference in the mean count of partially remodeled vessels or vessels completely lacking remodeling according to the lacunae score and grade of placental invasiveness. EVT cells were arranged in superficial confluent sheets or superficial irregular clusters, or were scattered deep below the basal plate.

CONCLUSION

Placental ultrasound and histopathologic features associated with PAS are more pronounced in invasive cases suggesting that they are secondary to the haemodynamic effects of abnormally deep placentation and transformation of the radial and arcuate arteries.

Immune cell infiltrate at the utero-placental interface is altered in placenta accreta spectrum disorders

PURPOSE

To characterize the immune cell infiltrate associated with maternal vascular remodeling in 12 cases of cesarean hysterectomy from women with placenta accreta spectrum (PAS) disorder.

METHODS

Myometrial vessels were evaluated by hematoxylin and eosin and immunohistochemistry stains on tissue microarrays that included samples from the myometrium, deep to the implantation site. Vessels were quantified based on physiologic conversion and immune cell infiltrates. Placental bed biopsies from cases of repeat cesarean section, and decidual vessels from delivered non-PAS placentas were used as controls.

RESULTS

Immune cells, predominantly macrophages and T-cells, were present as a band along the placental-myometrial interface in PAS cases. However, within the myometrium, the infiltrate showed a perivascular accentuation. The infiltrates around and within vessel walls were composed of T-cells (CD3) and macrophages (CD68), with fewer NK (CD56), Treg (FoxP3) and rare B-cells (CD20). Plasma cells (CD138) were absent. The majority of vessels with immune cell infiltrates had undergone complete or partial physiologic conversion by trophoblast. However, a subset of unconverted vessels in the myometrium had a similar immune cell infiltration. Control blood vessels showed a similar pattern of leukocytes infiltration in the decidua and placental bed biopsies, but with a lower density.

CONCLUSIONS

Our findings suggest that myometrial vascular changes in PAS resemble the physiological changes of vessels noted in the implantation site of normal pregnancies. The presence of perivascular immune cell infiltrates in the absence of adjacent trophoblast suggests that the process may be initiated by paracrine effects rather than direct contact or endovascular growth of trophoblast.

Trophoblast invasion: Lessons from abnormally invasive placenta (placenta accreta)

The invasion of the uterine wall by extravillous trophoblast is acknowledged as a crucial component of the establishment of pregnancy however, the only part of this process that has been clearly identified is the differentiation of cytotrophoblast (CTB) into the invasive extravillous trophoblast (EVT). The control of invasion, both initiation and termination, have yet to be elucidated and even the mechanism of differentiation is unclear. This review describes our studies which are designed to characterize the intracellular mechanisms that drive differentiation. We have used the over-invasion observed in abnormally invasive placenta (AIP; placenta accreta) to further interrogate this mechanism. Our results show that first trimester CTB to EVT differentiation is accomplished via an epithelial-mesenchymal transition (EMT), with EVT displaying a metastable, mesenchymal phenotype. In the third trimester, while the invasiveness of the EVT is lost, these cells still demonstrate signs of the EMT, albeit diminished. EVT isolated from AIP pregnancies do not however, show the same degree of reduction in EMT shown by normal third trimester cells. They exhibit a more mesenchymal phenotype, consistent with a legacy of greater invasiveness. The master regulatory transcription factor controlling the EMT appears, from the observational data, to be ZEB2 (zinc finger E-box binding protein 2). We verified this by overexpressing ZEB2 in the BeWo and JEG3 trophoblast cell lines and showing that they became more stellate in shape, up-regulated the expression of EMT-associated genes and demonstrated a substantially increased degree of invasiveness. The identification of the differentiation mechanism will enable us to identify the factors controlling invasion and those aberrant processes which generate the abnormal invasion seen in pathologies such as AIP and preeclampsia.

The role of the renin-angiotensin system in regulating endometrial neovascularization during the peri-implantation period: literature review and preliminary data

BACKGROUND

Implantation is initiated when the blastocyst attaches to the endometrium during the peri-implantation period, and appropriate neovascularization is a prerequisite for the success of the subsequent process. The role of the renin-angiotensin system (RAS) in regulation of blood pressure and hydro-electrolyte balance has long been recognized, while its role in the peri-implantation endometrium remains unclear. This manuscript discusses endometrial RAS and its possible pathways in regulating endometrial angiogenesis and its influence on subsequent pregnancy outcomes.

METHODS

A comprehensive search of electronic databases was carried out to identify relevant published articles, and a literature review was then performed. Using immunohistochemistry, we also performed a pilot study to examine expression of angiotensin II receptors, including angiotensin II type 1 (AT1) receptor (AT1-R) and angiotensin II type 2 (AT2) receptor (AT2-R) in the human endometrium around the time of implantation.

RESULTS

The results of the pilot study showed expression of AT1-R and AT2-R in all endometrial compartments (luminal epithelium, glandular epithelium, stroma cells, and blood vessels), and altered expression was witnessed in women with recurrent miscarriage when compared with fertile control women from our preliminary result.

CONCLUSION

Altered vasculature of the endometrium in the peri-implantation period is detrimental to implantation and may lead to recurrent miscarriage. Being an angiogenic mediators, endometrial RAS may play a role around the time of embryo implantation, affecting subsequent pregnancy outcomes.

Can introvoxel incoherent motion MRI be used to differentiate patients with placenta accreta spectrum disorders?

BACKGROUND

The incidence of PAS disorders increased rapidly in recent years, and introvoxel incoherent motion (IVIM) MRI has been applied in the assessment of placenta. The study aims to investigate whether the parameters from IVIM can be used to differentiate patients with PAS disorders complicating placenta previa and secondly to differentiate different categories of PAS disorders.

METHODS

The study participants were comprised of 99 patients with placenta previa, including 16 patients with placenta accreta, 51 patients with increta, 8 patients with percreta and 24 patients without PAS disorders between 28 + 0 and 39 + 6 weeks. IVIM MRI was performed on a 1.5 T scanner. Perfusion fraction (f), pseudodiffusion coefficient (D*) and diffusion coefficient (D) were calculated.

RESULTS

Women with PAS disorders had a higher perfusion fraction (p = 0.019) than women without the disease. Multiple comparisons showed perfusion fraction in patients without PAS disorders was significantly lower than in patients with placenta accreta and percreta(P = 0.018 and 0.033 respectively), but was not lower than in patients with increta(p = 1).

CONCLUSION

Patients with placenta accreta and percreta differed in placental perfusion fraction from women with increta and without PAS disorders.

Placental Implantation Disorders

Primary disorders of placental implantation have immediate consequences for the outcome of a pregnancy. These disorders have been known to clinical science for more than a century, but have been relatively rare. Recent epidemiologic obstetric data have indicated that the rise in their incidence over the last 2 decades has been iatrogenic in origin. In particular, the rising numbers of pregnancies resulting from in vitro fertilization (IVF) and the increased use of caesarean section for delivery have been associated with higher frequencies of previa implantation, accreta placentation, abnormal placental shapes, and velamentous cord insertion. These disorders often occur together.

Efficacy of tranexamic acid in reducing blood loss, blood and blood products requirements in Cesarian sections for patients with placenta accreta

Background

Placenta accreta is an obstetric emergency and the main cause of maternal morbidity and mortality due to the associated bleeding and coagulopathy. Tranexamic acid has been widely used to decrease blood loss in trauma patients and patients with postpartum hemorrhage. We aimed at studying the effect of tranexamic acid in reducing blood loss and blood transfusion in patients with placenta accreta.

Methods

In a double-blinded randomized controlled study, 46 patients were recruited and divided into two groups, Group A is the tranexamic group where patients received 10 mg/kg tranexamic acid after cord clamping and continued on tranexamic infusion 10 mg/kg/h till the end of the surgery. Group B is the placebo where patients received normal saline instead. Primary outcome was the amount of intraoperative blood loss, and other outcomes included the number of blood and blood products transfused intraoperative and in the first 24 h postoperative, the immediate postoperative Hb level, platelet count, and coagulation profile. Data were collected, coded, tabulated, and then analyzed using Minitab® 16.1.0 statistics software package. Variables were presented as mean and standard deviation and analyzed using unpaired t test. Any difference with p value < 0.05 was considered statistically significant.

Results

Amount of intraoperative blood loss was significantly less in the tranexamic group 2232 ± 1204 ml compared to the placebo group 3405 ± 1193 ml (p value 0.002), and patients in the tranexamic group received less units of packed red blood cells, fresh frozen plasma, and platelets compared to those in the placebo group (4.2 ± 1.9 vs 6.1 ± 2.2 with p value 0.003, 3.4 ± 1.3 vs 4.2 ± 1.2 with P value 0.036 and 4.8 ± 2.1 vs 6.2 ± 2.4 with p value 0.041, respectively). There was no statistically significant difference in the first postoperative Hb level, platelet count, and coagulation profile between the two groups; however, the amount of blood and products transfused in the first 24 h postoperative were significantly less in the tranexamic group

Conclusion

Tranexamic acid infusion was effective in reducing intraoperative blood loss and intraoperative and postoperative blood and blood products’ transfusion.

Placenta Accreta in an Oragnutan (Pongo abelii) and a Chimpanzee (Pan troglodytes)

Placenta accreta is defined as abnormal adherence of the placenta to the uterine wall. Placenta accreta is recognized as a common problem in human medicine, but has apparently not been reported previously in great apes, despite similarity in their reproductive biology. A 36-year-old multiparous female Sumatran orangutan (Pongo abelii) and a 20-year-old nulliparous female chimpanzee (Pan troglodytes), with gross uterine and histological uterine vascular changes that are characteristic of placenta accreta, are presented.

Impact of placenta previa with placenta accreta spectrum disorder on fetal growth

OBJECTIVES

To evaluate fetal growth in pregnancies complicated by placenta previa with or without placenta accreta spectrum (PAS) disorder, compared with in pregnancies with a low-lying placenta.

METHODS

This was a multicenter retrospective cohort study of singleton pregnancies complicated by placenta previa with or without PAS disorder, for which maternal characteristics, ultrasound-estimated fetal weight and birth weight were available. Four maternal-fetal medicine units participated in data collection of diagnosis, treatment and outcome. The control group comprised singleton pregnancies with a low-lying placenta (0.5-2 cm from the internal os). The diagnosis of PAS and depth of invasion were confirmed at delivery using both a predefined clinical grading score and histopathological examination. For comparison of pregnancy characteristics and fetal growth parameters, the study groups were matched for smoking status, ethnic origin, fetal sex and gestational age at delivery.

RESULTS

The study included 82 women with placenta previa with PAS disorder, subdivided into adherent (n = 35) and invasive (n = 47) PAS subgroups, and 146 women with placenta previa without PAS disorder. There were 64 controls with a low-lying placenta. There was no significant difference in the incidence of small-for-gestational age (SGA) (birth weight ≤ 10^th percentile) and large-for-gestational age (LGA) (birth weight ≥ 90^th  percentile) between the study groups. Median gestational age at diagnosis was significantly lower in pregnancies with placenta previa without PAS disorder than in the low-lying placenta group (P = 0.002). No significant difference was found between pregnancies complicated by placenta previa with PAS disorder and those without for any of the variables. Median estimated fetal weight percentile was significantly lower in the adherent compared with the invasive previa-PAS subgroup (P = 0.047). Actual birth weight percentile at delivery did not differ significantly between the subgroups (P = 0.804).

CONCLUSIONS

No difference was seen in fetal growth in pregnancies complicated by placenta previa with PAS disorder compared with those without and compared with those with a low-lying placenta. There was also no increased incidence of either SGA or LGA neonates in pregnancies with placenta previa and PAS disorder compared with those with placenta previa with spontaneous separation of the placenta at birth. Adverse neonatal outcome in pregnancies complicated by placenta previa and PAS disorder is linked to premature delivery and not to impaired fetal growth. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Pathophysiology of Placenta Accreta Spectrum Disorders: A Review of Current Findings

Current findings continue to support the concept of a biologically defective decidua rather than a primarily abnormally invasive trophoblast. Prior cesarean sections increase the risk of placenta previa and both adherent and invasive placenta accreta, suggesting that the endometrial/decidual defect following the iatrogenic creation of a uterine myometrium scar has an adverse effect on early implantation. Preferential attachment of the blastocyst to scar tissue facilitates abnormally deep invasion of trophoblastic cells and interactions with the radial and arcuate arteries. Subsequent high velocity maternal arterial inflow into the placenta creates large lacunae, destroying the normal cotyledonary arrangement of the villi.

Trophoblast function is altered by decidual factors in gestational-dependant manner

Inadequate implantation and placentation is associated with miscarriage and placental insufficiency. The decidual environment is thought to regulate trophoblast invasion, however this is poorly defined in humans. We aimed to determine the effect of decidualization on trophoblast function. In vitro decidualized primary human endometrial stromal cells (HESC) significantly enhanced first-trimester extravillous trophoblast (EVT) (6-8-weeks gestation) adhesion, outgrowth/invasion. In EVTs from 10 to 12-weeks gestation this effect was absent (adhesion, invasion) or reversed (outgrowth). HESC conditioned media had no effect on trophoblast MMP9 production/activity. Decidualization regulated EVT function in a gestational-dependent manner. This study highlights the importance of trophoblast-decidual synchrony.

Downregulation of MicroRNA-125a in Placenta Accreta Spectrum Disorders Contributes Antiapoptosis of Implantation Site Intermediate Trophoblasts by Targeting MCL1

The typical hallmark of placenta accreta spectrum (PAS) disorders is increased implantation site intermediate trophoblast (ISIT) cell numbers. However, the extent of trophoblast proliferation and apoptosis have not been found to differ from those of normal placentation. MicroRNA-125a (miR-125a) induces apoptosis in colon cancer cell by targeting myeloid cell leukemia-1 gene (MCL1). We aimed to investigate the influence of miR-125a on ISIT cells in PAS disorders in 15 patients (self-paired trials) with placenta previa and PAS disorders. Expression of miR-125a and MCL1 were measured in villous trophoblasts and basal plate myometrial fibers from creta site and adjacent noncreta tissues by real-time quantitative polymerase chain reaction, and expression of the MCL1 protein was assayed by Western blotting. Flow-cytometry was used to examine the effect of miR-125a overexpression on apoptosis in vitro in HTR-8/SVneo cells, and luciferase activity assays was used to confirm miR-125a targeting of MCL1. In vivo, the expression levels of miR-125a was significantly lower in creta versus noncreta tissues, and the expression of MCL1 was upregulated; moreover, immunohistochemistry showed that the increased ISIT cells in the creta were positive for MCL1 protein. MCL1 was downregulated in the miR-125a-overexpressing HTR-8/SVneo cells in vitro, and overexpression of miR-125a-induced apoptosis in the HTR-8/SVneo trophoblast line. Finally, luciferase activity assays confirmed that miR-125a directly target the 3' untranslated region of MCL1 in the 293T cell line. In conclusion, downregulation of MCL1-targeting miR-125a exerts an antiapoptotic effect on ISIT cells in PAS disorders.

ZEB2, a master regulator of the epithelial-mesenchymal transition, mediates trophoblast differentiation

STUDY QUESTION

Does the upregulation of the zinc finger E-box binding homeobox 2 (ZEB2) transcription factor in human trophoblast cells lead to alterations in gene expression consistent with an epithelial-mesenchymal transition (EMT) and a consequent increase in invasiveness?

SUMMARY ANSWER

Overexpression of ZEB2 results in an epithelial-mesenchymal shift in gene expression accompanied by a substantial increase in the invasive capacity of human trophoblast cells.

WHAT IS KNOWN ALREADY

In-vivo results have shown that cytotrophoblast differentiation into extravillous trophoblast involves an epithelial-mesenchymal transition. The only EMT master regulatory factor which shows changes consistent with extravillous trophoblast EMT status and invasive capacity is the ZEB2 transcription factor.

STUDY DESIGN, SIZE, DURATION

This study is a mechanistic investigation of the role of ZEB2 in trophoblast differentiation. We generated stable ZEB2 overexpression clones using the epithelial BeWo and JEG3 choriocarcinoma lines. Using these clones, we investigated the effects of ZEB2 overexpression on the expression of EMT-associated genes and proteins, cell morphology and invasive capability.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We used lentiviral transduction to overexpress ZEB2 in BeWo and JEG3 cells. Stable clones were selected based on ZEB2 expression and morphology. A PCR array of EMT-associated genes was used to probe gene expression. Protein measurements were performed by western blotting. Gain-of-function was assessed by quantitatively measuring cell invasion rates using a Transwell assay, a 3D bioprinted placenta model and the xCelligenceTM platform.

MAIN RESULTS AND THE ROLE OF CHANCE

The four selected clones (2 × BeWo, 2 × JEG3, based on ZEB2 expression and morphology) all showed gene expression changes indicative of an EMT. The two clones (1 × BeWo, 1 × JEG3) showing >40-fold increase in ZEB2 expression also displayed increased ZEB2 protein; the others, with increases in ZEB2 expression <14-fold did not. The two high ZEB2-expressing clones demonstrated robust increases in invasive capacity, as assessed by three types of invasion assay. These data identify ZEB2-mediated transcription as a key mechanism transforming the epithelial-like trophoblast into cells with a mesenchymal, invasive phenotype.

LARGE SCALE DATA

PCR array data have been deposited in the GEO database under accession number GSE116532.

LIMITATIONS, REASONS FOR CAUTION

These are in-vitro studies using choriocarcinoma cells and so the results should be interpreted in view of these limitations. Nevertheless, the data are consistent with in-vivo findings and are replicated in two different cell lines.

WIDER IMPLICATIONS OF THE FINDINGS

The combination of these data with the in-vivo findings clearly identify ZEB2-mediated EMT as the mechanism for cytotrophoblast differentiation into extravillous trophoblast. Having characterized these cellular mechanisms, it will now be possible to identify the intracellular and extracellular regulatory components which control ZEB2 and trophoblast differentiation. It will also be possible to identify the aberrant factors which alter differentiation in invasive pathologies such as preeclampsia and abnormally invasive placenta (AKA accreta, increta, percreta).

STUDY FUNDING AND COMPETING INTEREST(s)

Funding was provided by the Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine and Surgery at Hackensack Meridian Health, Hackensack, NJ. The 3D bioprinted placental model work done in Drs Kim and Fisher's labs was supported by the Children's National Medical Center. The xCELLigence work done in Dr Birge's lab was supported by NIH CA165077. The authors declare no competing interests.

Preoperative cystoscopy could determine the severity of placenta accreta spectrum disorders: An observational study

AIM

In the surgical treatment of placenta accreta spectrum disorders, cystoscopy for prophylactic stent placement is performed to protect the ureters from potential injury. Despite its frequent use, the use of cystoscopy in assessing the severity of these disorders has not been explored. Our objective was to find out if the abnormal findings documented during cystoscopy are associated with disease severity.

METHODS

In this retrospective, observational cohort study (n = 56), the bladder wall was evaluated at the time of ureteral stent placement via cystoscopy in prenatally diagnosed placenta accreta spectrum cases. Three abnormal findings were commonly present in these cases: bulging of the posterior bladder wall, neovascularization and arterial pulsatility in the area of neovascularization. These findings were stratified according to severity in histologically confirmed specimens. Continuous variables were compared via two-tailed t-tests and Wilcoxon rank sum tests. Categorical data were evaluated using logistic regression analysis.

RESULTS

Neovascularization affected 84%, bulging 71% and pulsatility 54% of the cases. Bulging and neovascularization increased with disease severity. Pulsatility occurred exclusively in percretas. Bulging was associated with a 12-fold (OR = 11.6, 95% CI 2.94-46.33, P = 0.0005) increased likelihood of percreta and neovascularization with a 17-fold (OR = 17.06, 95% CI 2.98-97.79, P = 0.0014) increase. Neovascularization and/or the presence of bulging of the bladder have high positive predictive value for placenta increta and percreta (91.5% and 95.0%, respectively). Cystoscopy can be used to assess the severity of placenta accreta spectrum cases preoperatively, especially when placentation is over the previous uterine scar and is in proximity to the bladder wall.

Chorion laeve accreta - Another manifestation of morbid adherence

INTRODUCTION

Smooth muscle in the decidua of fetal membranes (membrane myofibers, MMF) is not mentioned in standard textbooks.

METHODS

The current report presents collected observations on 52 patients with MMF at 2 institutions between 2004 and 2017 - including placentas, postpartum curettages, and hysterectomies.

RESULTS

Clinical presentations include observation of adherent membranes during delivery, disrupted and incomplete membranes in placentas submitted for examination, postpartum bleeding associated with retained fetal membranes, association with membrane hematomas and membrane hemosiderin, morbidly adherent fetal membranes in hysterectomies; and association with grossly adherent pieces of tissue or nodules in fetal membranes.

DISCUSSION

Although MMF can be an incidental microscopic observation in a routine placenta, the suggested diagnostic terminology when there are clinical and/or gross presentations is Chorion Laeve Accreta (ChLA). Further study is needed but MMF appears to be the fetal membrane counterpart of BPMF(basal plate myofibers), possibly due to damage of subjacent myometrium by trophoblastic proteases, so that shear stress during delivery causes myofibers to come out attached to the decidua of fetal membranes. Neither the prevalence of MMF, nor its reliability as a marker for placenta accreta is addressed in this collection. Association of MMF with BPMF, and recurrence of MMF, are documented; but the true frequency of these phenomena remains to be established.

Prenatal Diagnosis of Abnormal Invasive Placenta by Ultrasound: Measurement of Highest Peak Systolic Velocity of Subplacental Blood Flow

The aim of the study described here was to identify an efficient criterion for the prenatal diagnosis of abnormal invasive placenta. We evaluated 129 women with anterior placenta previa who underwent trans-abdominal ultrasound evaluation in the third trimester. Spectral Doppler ultrasonography was performed to assess the subplacental blood flow of the anterior lower uterine segment by measuring the highest peak systolic velocity and resistive index. These patients were prospectively followed until delivery and evaluated for abnormal placental invasion. The peak systolic velocity and resistive index of patients with and without abnormal placental invasion were then compared. Postpartum examination revealed that 55 of the patients had an abnormal invasive placenta, whereas the remaining 74 did not. Patients with abnormal placental invasion had a higher peak systolic velocity of the subplacental blood flow in the lower segment of the anterior aspect of the uterus (area under receiver operating characteristic curve: 0.91; 95% confidence interval: 0.87-0.96) than did those without abnormal placental invasion. Our preliminary investigations suggest that a peak systolic velocity of 41 cm/s can be considered a cutoff point to diagnose abnormal invasive placenta, with both good sensitivity (87%) and good specificity (78%), and the higher the peak systolic velocity, the greater is the chance of abnormal placental invasion. Resistive index had no statistical significance (area under receiver operating characteristic curve, 0.56; 95% confidence interval: 0.46-0.66) in the diagnosis of abnormal invasive placenta. In conclusion, measurement of the highest peak systolic velocity of subplacental blood flow in the anterior lower uterine segment can serve as an additional marker of anterior abnormal invasive placenta.

Placenta accreta spectrum: pathophysiology and evidence-based anatomy for prenatal ultrasound imaging

Placenta accreta spectrum is a complex obstetric complication associated with high maternal morbidity. It is a relatively new disorder of placentation, and is the consequence of damage to the endometrium-myometrial interface of the uterine wall. When first described 80 years ago, it mainly occurred after manual removal of the placenta, uterine curettage, or endometritis. Superficial damage leads primarily to an abnormally adherent placenta, and is diagnosed as the complete or partial absence of the decidua on histology. Today, the main cause of placenta accreta spectrum is uterine surgery and, in particular, uterine scar secondary to cesarean delivery. In the absence of endometrial reepithelialization of the scar area the trophoblast and villous tissue can invade deeply within the myometrium, including its circulation, and reach the surrounding pelvic organs. The cellular changes in the trophoblast observed in placenta accreta spectrum are probably secondary to the unusual myometrial environment in which it develops, and not a primary defect of trophoblast biology leading to excessive invasion of the myometrium. Placenta accreta spectrum was separated by pathologists into 3 categories: placenta creta when the villi simply adhere to the myometrium, placenta increta when the villi invade the myometrium, and placenta percreta where the villi invade the full thickness of the myometrium. Several prenatal ultrasound signs of placenta accreta spectrum were reported over the last 35 years, principally the disappearance of the normal uteroplacental interface (clear zone), extreme thinning of the underlying myometrium, and vascular changes within the placenta (lacunae) and placental bed (hypervascularity). The pathophysiological basis of these signs is due to permanent damage of the uterine wall as far as the serosa, with placental tissue reaching the deep uterine circulation. Adherent and invasive placentation may coexist in the same placental bed and evolve with advancing gestation. This may explain why no single, or set combination of, ultrasound sign(s) was found to be specific for the depth of abnormal placentation, and accurate for the differential diagnosis between adherent and invasive placentation. Correlation of pathological and clinical findings with prenatal imaging is essential to improve screening, diagnosis, and management of placenta accreta spectrum, and standardized protocols need to be developed.

Senescence and Telomere Homeostasis Might Be Involved in Placenta Percreta-Preliminary Investigation

OBJECTIVE

Placenta percreta (PP) is an abnormal condition of trophoblast maturation and terminal differentiation through the uterine wall. We opted to study telomere homeostasis and senescence expression in trophoblasts from PP, the most severe subgroup of placenta accreta.

STUDY DESIGN

Paraffin-embedded placental biopsies from pregnancies with percreta and normal placentation, matched by gestational age at delivery, were assessed for telomere length, aggregates, and senescence-associated heterochromatin foci using quantitative fluorescence in situ hybridization. Cyclin-dependent kinase inhibitors p21, p15, p16, and the tumor suppressor protein p53, known senescence-related markers, were assessed using immunohistochemical staining.

RESULTS

Short telomeres were found more often in trophoblasts from the samples of PP (n = 9) compared to controls (n = 8; 54% ± 20% vs 2.3% ± 1.16%, respectively; P < .05). More cells with telomere aggregates (18.3% ± 6.9%) were observed in the PP than in the control group (4.8% ± 5.4%; P = .0005). The percentage of nucleic senescence-associated heterochromatin foci in the PP and control samples was similar (10.9% ± 10.4% vs 10.7% ± 15%, respectively; P = .97). Immunohistochemistry of senescence markers was expressed differently in PP compared to the controls: higher p15 expression (46.42% ± 15.2% vs 36.63% ± 12.2%, P = .004), higher p21 expression (59.8% ± 22.1% vs 47.5% ± 21.9%, P = .011), lower p16 expression (54.8% ± 26.3% vs 73.4% ± 18.9%, P = .000), and lower p53 expression (24.4% ± 33.8% vs 34% ± 14.4%, P = .000).

CONCLUSION

Placenta percreta exhibits telomere alterations and changes in expression of several senescence markers. These might be related to altered trophoblast invasion maturation and placental detachment postpartum.

Anterior placenta previa is associated with increased umbilical cord blood hematocrit concenrations

OBJECTIVE

We aimed to evaluate the umbilical cord blood (CB) hematocrit (Hct) levels in women with anterior located placenta previa (PP).

METHODS

This is a prospective case-control study performed in a tertiary level maternity hospital. Thirty seven pregnant women diagnosed with anterior PP (study group) and 37 women without PP (control group) included into the study. Groups were matched with regard to age, gestational age, and fetal gender. All women underwent Cesarean section. Umbilical CB Hct levels of the newborns were measured. Demographics, operative features, and neonatal outcomes were recorded.

RESULTS

Umbilical CB Hct levels were statistically significantly higher in the PP patients compared with controls (p: 52.6±5.0 vs. 47.5±5.0, p < 0.001). Preoperative maternal hemoglobin (Hgb) and Hct levels were similar in the two groups. However, postoperative Hb and Hct levels were significantly lower in the study group (p: 0.003, p < 0.001, respectively). Intraoperative complication rates were higher in this group. Neonatal Apgar scores were lower and neonatal intensive care unit admission was more common in the PP group when compared with controls.

CONCLUSION

We think that anterior PP is associated with increased umbilical CB Hct levels. Neonatologists should consider this condition in the infants born to mothers with anterior PP.

The depletion of MARVELD1 leads to murine placenta accreta via integrin β4-dependent trophoblast cell invasion

The placenta is a remarkable organ, it serves as the interface between the mother and the fetus. Proper invasion of trophoblast cells is required for a successful pregnancy. Previous studies have found that the adhesion molecule integrin β4 plays important roles during trophoblast cell invasion. Here, we found that the overall birth rate of the MARVELD1 knockout mouse is much lower than that of the wild-type mouse (p < 0.001). In E18.5 MARVELD1 knockout mice, we observed an over-invasion of trophoblast cells, and indeed, the pregnant mice had a partial placenta accreta phenotype. The HTR8/SVneo cell line was used as an in vitro model to elucidate the underlying mechanisms of MARVELD1-mediated trophoblast invasion. We detected a diminished expression of integrin β4 upon the downregulation of MARVELD1 and enhanced migrate and invasive abilities of trophoblast cells both in vivo and in vitro. The integrin β4 rescue assay also supported the results. In conclusion, this study found that MARVELD1 mediated the invasion of trophoblast cells via regulating the expression of integrin β4 during placenta development.

Prophylactic occlusion balloon placement in internal iliac arteries for the prevention of postpartum haemorrhage due to morbidly adherent placenta: short term outcomes

PURPOSE

To evaluate outcomes of uterine conserving surgery with occlusion balloon technique. A critical review of the complications was performed.

MATERIALS AND METHODS

Between 2010 and 2016, pregnant women, with a prenatal diagnosis of morbidly adherent placenta (MAP), were treated with occlusion balloon catheters in both internal iliac arteries. Parameters such as need for hysterectomy, incidence of PPH, grade of MAP, estimated blood loss during delivery (EBL) and transfusion requirements, mean recovery time and duration of the balloon inflation, were collected and reviewed. Complications requiring further management were analysed.

RESULTS

Thirty-seven women with MAP underwent prophylactic occlusion balloon placement (POBC). Mean recovery was 4.48 days (range 2-10). Catheters were successfully positioned and balloons inflated in obstetric theatre following caesarean delivery in 100% of the cases. The uterus was conserved in every case. The MAP grades were 20 percreta, 3 increta and 14 accreta. The EBL was not statistically different between the different grades of placentation. There was a statistically significant association in the number of patients requiring blood transfusions and the degree of placental invasion (p = 0. 0119). PPH occurred in 5 patients (13.5%) and arterial thrombosis in 4 patients (11%). The EBL during delivery was significantly higher (2811 mL) in patients with complications (p = 0.0102). Furthermore, the group of patients that had complications required statistically significant more blood transfusions compared to those without complications (p = 0.0001). No maternal mortality or foetal morbidity occurred.

CONCLUSION

The utilisation of Prophylactic occlusion balloon catheters allows uterine conserving surgery to be performed safely with few maternal complications.

Human extravillous trophoblast invasion: intrinsic and extrinsic regulation

During the establishment of pregnancy, a human blastocyst implants into the uterine endometrium to facilitate the formation of a functional placenta. Implantation involves the blastocyst adhering to the uterine luminal epithelium before the primitive syncytiotrophoblast and subsequently specialised cells, the extravillous trophoblast (EVT), invade into the decidua in order to engraft and remodel uterine spiral arteries, creating the placental blood supply at the end of the first trimester. Defects in EVT invasion lead to abnormal placentation and thus adverse pregnancy outcomes. The local decidual environment is thought to play a key role in regulating trophoblast invasion. Here we describe the major cell types present in the decidua during the first trimester of pregnancy and review what is known about their regulation of EVT invasion. Overall, the evidence suggests that in a healthy pregnancy almost all cell types in the decidua actively promote EVT invasion and, further, that reduced EVT invasion towards the end of the first trimester is regulated, in part, by the reduced invasive capacity of EVTs shown at this time.

Histopathology of Placenta Creta: Chorionic Villi Intrusion into Myometrial Vascular Spaces and Extravillous Trophoblast Proliferation are Frequent and Specific Findings With Implications for Diagnosis and Pathogenesis

Placenta creta is characterized by invasion of placental villi into the myometrium in the setting of a dysfunctional or absent decidua. Histopathologic diagnosis of placenta creta is important, particularly in cases of hysterectomy because of unanticipated intractable postpartum hemorrhage. Previous studies have documented a higher amount and depth of myometrial infiltration by the implantation site intermediate trophoblast compared with controls. In addition, we have anecdotally observed chorionic villi in myometrial vascular spaces in specimens with placenta creta. The aim of this study was to explore the prevalence and specificity of these features. Sixty-one postpartum hysterectomies, 44 with placenta creta and 17 without were reviewed. Villous intrusion into vascular spaces was recorded. Using immunohistochemistry for GATA3, the amount of intermediate trophoblast (number of positive cells in five 40× fields) and depth of trophoblast myometrial infiltration were assessed. Mean gestational ages of the creta group (34.4 yr; range, 20-43 yr) and control group (35 yr; range, 25-51 yr) were comparable. Presence of chorionic villi in myometrial vascular spaces was frequent in placenta creta: 31/44 versus 1/17 controls (70.4% vs. 5.8%, P<0.0001). This finding was more common in the percreta (87.5%) and increta (84%) than in the accreta (27.2%, P=0.0008). Mean depth of trophoblast myometrial invasion was greater in cretas (47.9%) than in controls (14.5%, P=0.004). Likewise, mean distance of deepest trophoblast to serosa was shorter in the cretas (7.3 mm) than in controls (23.8 mm, P<0.0001). These differences were, however, attributable to placentas increta and percreta. When only accretas and controls were compared, the myometrial depth of trophoblast was similar. The mean intermediate trophoblast cell count in the placental bed was greater in cretas (664) than in controls (288, P<0.0001). Such difference was seen in all creta cases despite the type (accreta 639, increta 676, percreta 661). A trophoblast count of ≥100 cells/high-power field was seen in 75.8% of cretas and 11.1% of controls (P=0.0009). For the first time, we document the finding of chorionic villi intrusion into myometrial vascular spaces, which is highly specific of placenta creta. In addition, assessment of the amount of intermediate trophoblast using GATA3 immunohistochemistry can assist in the diagnosis. We hypothesize that placental invasion in placenta creta is due, at least partially, to transformation of low-resistance myometrial vessels leading to subsequent protrusion of villi into their lumens, in the context of absent decidua.

Placenta Increta Presenting as Exaggerated Placental Site Reaction

Exaggerated placental site (EPS) is usually an incidental finding seen in curettings after an abortion. Placenta increta is, by definition, a disease that damages and destroys myometrium; however, prior literature has not paid sufficient attention to the role of myometrium in its pathogenesis and diagnosis. We present an unusual case of placenta increta in a hysterectomy performed for uterine perforation after curettage for the termination of pregnancy at 18 weeks. The initial histologic section of the implantation site suggested EPS. Actin stains showed degenerated inflamed muscle at the EPS-like site, keratin stains showed interstitial trophoblast in the zone of myometrial damage, and the wall of the corpus was grossly thinned under the placenta. The myometrial damage may have softened the wall, predisposing to uterine perforation by the curettage procedure.

[Features of cytotrophoblast invasion in complete placenta previa and increta]

AIM

to investigate the characteristics of cytotrophoblast invasion in complete placenta previa and increta.

MATERIAL AND METHODS

Three groups of placentas and amputated uteri were examined. These were: 1) 10 placentas at 20-22 weeks' gestation after drug-induced abortion; 2) 4 uteri with typical placentation at 34-36 weeks and wall ruptures; 3) 12 uteri with ultrasound-confirmed complete placenta previa and subsequent hysterectomy (at 34-36 weeks.) due to massive bleeding. In all cases, the sections were stained with hematoxylin and eosin, azan by the Mallory's method; immunovisualization of invasive cells with the marker cytokeratin 8 was also used. In Groups 2 and 3, the uterine distribution density of invasive cells was compared in a standard slice area (×200) separately, within the endometrium and myometrium.

RESULTS

Complete placenta previa was found to have the following characteristics: 1) all the uteri exhibited focal or diffuse friable, or thick scars after cesarean section; 2) multiple active anchor villi with villous cytotrophoblast layers, which were characteristic of Group 1 placentas and absent in the uteri women of Group 2; 3) bays diagnosed in the basal endometrium with ingrown villi (placenta increta); 4) a morphometrically significant increase in the distribution density of interstitial cytotrophoblast in the endometrium and only a similar trend in the myometrium. Invasive cells did not penetrate into the area of scars. Failure of the second wave of cytotrophoblast invasion was confirmed by incomplete gestational restructuring and partial obliteration of the myometrial radial arteries.

CONCLUSION

Real risks for severe clinical forms of abnormal placentation declare more stringent indications for surgical delivery.

Downregulation of miR-29a/b/c in placenta accreta inhibits apoptosis of implantation site intermediate trophoblast cells by targeting MCL1

OBJECTIVE

Placenta accreta is defined as abnormal adhesion of placental villi to the uterine myometrium. Although this condition has become more common as a result of the increasing rate of cesarean sections, the underlying causative mechanism(s) remain elusive. Because microRNA-29a/b/c (miR-29a/b/c) have been shown to play important roles in placental development, this study evaluated the roles of these microRNAs in placenta accreta.

METHODS

Expression of miR-29a/b/c and myeloid cell leukemia-1 (MCL1) were quantified in patient tissues and HTR8/SVneo trophoblast cells using the real-time quantitative polymerase chain reaction. Western blotting was used to analyze expression of the MCL1 protein in HTR8/SVneo trophoblast cells with altered expression of miR-29a/b/c. To determine their role in apoptosis, miR-29a/b/c were overexpressed in HTR-8/SVneo cells, and levels of apoptosis were analyzed by flow cytometry. Luciferase activity assays were used to determine whether MCL1 is a target gene of miR-29a/b/c.

RESULTS

Expression of miR-29a/b/c was significantly lower in creta sites compared to noncreta sites (p = 0.018, 0.041, and 0.022, respectively), but expression of MCL1 was upregulated in creta sites (p = 0.039). MCL1 expression was significantly downregulated in HTR-8/SVneo cells overexpressing miR-29a/b/c (p = 0.002, 0.008, and 0.013, respectively). Luciferase activity assays revealed that miR-29a/b/c directly target the 3' untranslated region of MCL1 in 293T cells. Over-expression of miR-29a/b/c induced apoptosis in the HTR-8/SVneo trophoblast cell line. Moreover, histopathological evaluation revealed that the number of implantation site intermediate trophoblast (ISIT) cells was increased in creta sites and that these cells were positive for MCL1.

CONCLUSIONS

Our results demonstrate that in placenta accreta, miR-29a/b/c inhibits apoptosis of ISIT cells by targeting MCL1. These findings provide new insights into the pathogenesis of placenta accreta.

Expression of Epithelial-Mesenchymal Transition-related Factors in Adherent Placenta

Epithelial-mesenchymal transition is a key process influencing cancer progression and metastasis. The purpose of this study was to investigate the expression of epithelial-mesenchymal transition-related factors in chorionic villi and decidual cells in adherent placenta. The current study included 19 patients diagnosed with adherent placenta after hysterectomy. The expression of E-cadherin, Vimentin, Snail, and transforming growth factor-β in placental tissues was analyzed by immunohistochemical staining. Immunostaining intensity was semiquantitatively evaluated using the HSCORE algorithm. In the chorionic villi of the invasive part (placenta with invasion into myometrium), E-cadherin expression was significantly lower than that in the noninvasive part (placenta with no invasion). In the decidual cells of the invasive part, expression of transforming growth factor-β and Snail significantly increased. These results suggest that epithelial-mesenchymal transition may contribute to excessive trophoblast invasion into the myometrium in adherent placenta.

Placenta accreta and anesthesia: A multidisciplinary approach

Placenta accreta (an abnormally adherent placenta) is one of the two leading causes of peripartum hemorrhage and the most common indication for peripartum hysterectomy. Placenta accreta may be associated with significant maternal hemorrhage at delivery owing to the incomplete placental separation. When placenta accreta is diagnosed before delivery, a multidisciplinary approach may improve patient outcome.