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

The impact of preoperative ultrasound and intraoperative findings on surgical outcomes in patients at high-risk of placenta accreta spectrum

OBJECTIVE: To assess whether preoperative ultrasound imaging and intraoperative features predict surgical outcomes in patients at high-risk for placenta accreta spectrum (PAS). DESIGN: Cohort study. SETTING: Cairo University Maternity, Egypt. POPULATION OR SAMPLE: Pregnant patients with one or more prior cesarean delivery presenting with a low-lying/placenta previa with or without PAS confirmed by histopathology. METHODS: Logistic regression and multivariable analyses. MAIN OUTCOMES MEASURES: Need for primary cesarean hysterectomy, numbers of red blood cell (RBC) units transfused and patients requiring transfusion of > 5 units. RESULTS: Ninety consecutive records were reviewed including 58 (64.4%) PAS cases. Sixty (66.7%, 95%CI 56-76%) required hysterectomy. Odds of hysterectomy were significantly (P=.005) increased with complete previa. Significantly higher odds of hysterectomy were associated with subplacental hypervascularity (7.23, 95% CI 2.72;19.2, P 5 RBC units was associated with number of lacunae (OR 1.48, 95% CI 1.14;1.93, P=.004) and presence of feeder vessels (OR 1.62, 95% CI 1.24;2.11, P=.001). The multivariable analysis indicated that parity, placental location and PAS were significantly (P=.007; P=.01; P<.001, respectively) associated with hysterectomy. CONCLUSIONS: Preoperative ultrasound imaging can assist in triaging and counselling patients regarding the odds of PAS, intraoperative blood losses and need for hysterectomy whereas intraoperative features can assist the surgeon in evaluating the need for multidisciplinary support

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. OBJECTIVES: The aim of this study was to evaluate the role of transvaginal sonography in the third trimester 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, a history of at least one prior cesarean delivery and diagnosed prenatally with an anterior low-lying/placenta previa delivered electively after 32 weeks. All patients had a least one detailed ultrasound examination including transabdominal and transvaginal scans within two weeks prior to delivery. Two experienced operators, blinded to the clinical data were asked to make a judgement 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 cotyledon(s) 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 (68.5%) patients at birth and histologic examination confirmed superficial villous attachment (creta) and deep villous attachment (increta) in 11 and 65 cases, respectively. Seventy-two (64.9%) patients had a peripartum hysterectomy including 13 cases with no evidence of PAS at birth due to 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= 0.002) between transabdominal and transvaginal ultrasound examination but both ultrasound techniques had similar likelihood score in identifying accreta placentation that was confirmed at birth. On transabdominal scan, only a high lacuna score was significantly associated (p= 0.02) 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= 0.003), changes in the cervix structure (p= 0.01), cervix increased vascularity (p= 0.001), and the presence of placental lacunae (p= 0.005). The odds ratio for peripartum hysterectomy were 5.01 (95%CI 1.25;20.1) for a very thin (< 1mm) distal lower uterine segment and 5.62 (95%CI 1.41;22.5) 3+ lacuna score. CONCLUSION: Transvaginal ultrasound examination contribute to both prenatal management and to prediction of surgical outcomes in patients with a history of prior CD with and without ultrasound signs suggestive of PAS. 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, with or without signs suggesting PAS on imaging

A new methodologic approach for clinico-pathologic correlations in invasive placenta previa accreta.

BACKGROUND: The development of new management strategies for women presenting with placenta accreta spectrum requires quality epidemiology data, which have so far been limited by the high variability in clinical and histopathologic data confirming the diagnosis at birth. OBJECTIVE: To evaluate the role of a new methodologic approach for the correlation of clinical and pathological data for women with a history of prior cesarean delivery diagnosed prenatally with placenta previa accreta. MATERIALS AND METHODS: A modified pathologic technique for gross examination of hysterectomy specimens with placenta in situ consisting of intraoperative examination, immediate postoperative examination, and guided histologic sampling was used prospectively in a cohort of 24 patients with singleton pregnancies complicated by placenta low-lying/placenta previa accreta. Maternal characteristics, detailed ultrasound findings, surgical outcomes, and histopathologic examination were compared with those of a group of 24 patients with similar clinical characteristics and in whom a standard pathologic examination method was used. RESULTS: The median reporting time for obtaining the complete histopathology results including the microscopic examination was significantly shorter (7 versus 15 days; P < .001) and the median number of samples taken for histologic examination significantly lower (4 versus 14 samples; P < .001) in the study group than in the controls. The number of histologic slides showing villous invasion was significantly higher (2 versus 1 slide; P = .002), and the ratio of the number of samples taken to the numbers of slides confirming villous invasion was significantly lower (2 versus 9; P < .001) in the study group than in the controls. In all cases in the study group, intraoperative examination identified a dense tangled bed of vessels or multiple vessels running laterally and cranio-caudally in the uterine serosa above the placental insertion that were no longer visible during immediate gross postoperative examination of the hysterectomy specimens. Immediate postoperative dissection enables the differential diagnosis between focal and large increta areas, and between abnormally adherent placenta and invasive placenta accreta. CONCLUSION: Valuable clinical information on the serosal vascularity, uterine dehiscence, and extension of the accreta area is added with the description of the macroscopic examination during the surgical procedure and immediate dissection of the specimen. This methodological approach is cost-effective and increases the quality of the histologic sampling. It thus provides more accurate correlations with the clinical data and more accurate epidemiologic data collection. Perinatal pathologists should be part of multidisciplinary teams involved the management placenta accreta spectrum disorders