Intraplacental Fetal Vessel Diameter May Help Predict for Placental Invasiveness in Pregnant Women at High Risk for Placenta Accreta Spectrum Disorders.

Background Prenatal identification of placenta accreta spectrum (PAS) disorder is essential for treatment planning. More objective means for predicting PAS and clinical outcome may be provided by MRI descriptors. Purpose To investigate the association of intraplacental fetal vessel (IFV) diameter at MRI with PAS and peripartum complications. Materials and Methods Between March 2016 and October 2019, 160 gravid women suspected of having PAS underwent placental MRI as part of a prospective trial. Secondary analysis was performed by two experienced genitourinary radiologists for presence and maximum diameter of IFVs. Relative risk ratios were computed to test the association of IFVs with presence and depth of PAS invasiveness. Receiver operating characteristic analysis was used to evaluate the ability of IFV diameter to help predict PAS, placenta percreta, and peripartum complications and for comparison of the area under the curve (AUC) versus that from other combined MRI predictors of PAS (eg, myometrial thinning, intraplacental T2-hypointense bands, uterine bulge, serosal hypervascularity, and signs of extrauterine placental spread). Intraoperative and histopathologic findings were the reference standard. Results A total of 155 women were evaluated (mean age, 35 years ± 5 [standard deviation]; mean gestational age, 32 weeks ± 3). PAS was diagnosed in 126 of 155 women (81%) (placental percreta in 68 of 126 [54%]). At delivery, 30 of 126 women (24%) experienced massive blood loss (>2000 mL). IFVs were detected at MRI in 109 of 126 women with PAS (86%) and in 67 of 68 women with placental percreta (98%). The relative risk ratio was 2.4 (95% CI: 1.6, 3.4; P < .001) for PAS and 10 (95% CI: 1.5, 70.4; P < .001) for placental percreta when IFVs were visible. IFVs of 2 mm or greater were associated with PAS (AUC, 0.81; 95% CI: 0.67, 0.95; P = .04). IVFs of 3 mm or greater were associated with placenta percreta (AUC, 0.81; 95% CI: 0.73, 0.89; P < .001) and with peripartum complications, including massive bleeding (AUC, 0.80; 95% CI: 0.71, 0.89; P < .001). Combining assessment of IFVs with other MRI descriptors improved the ability of MRI to predict PAS (AUC, 0.94 vs 0.89; P = .009). Conclusion Assessment of intraplacental fetal vessels with other MRI descriptors improved the ability of MRI to help predict PAS. Vessel diameter of 3 mm or greater was predictive of placenta percreta and peripartum complications. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Dighe in this issue.

MRI prognosticators for adverse maternal and neonatal clinical outcome in patients at high risk for placenta accreta spectrum (PAS) disorders.

BACKGROUND: Placenta accreta spectrum (PAS) disorders may be associated with significant mortality and morbidity for both mother and fetus. PURPOSE/HYPOTHESIS: To identify MRI risk factors for poor peripartum outcome in gravid patients at risk for PAS. STUDY TYPE: Prospective. POPULATION: One hundred gravid women (mean age: 34.9 years) at third trimester, with placenta previa. FIELD STRENGTH/SEQUENCE: T2 -SSTSE (single-shot turbo spin echo), T2 -TSE, T1 -TSEFS (TSE images with fat-suppression) at 1.5T. ASSESSMENT: Fifteen MRI features considered indicative of PAS were recorded by three radiologists and were tested for any association with the following adverse peripartum maternal and neonatal events: increased operation time, profound blood loss, hysterectomy, bladder repair, ICU admission, prematurity, low birthweight, and 5-minute APGAR score <7. STATISTICAL TESTS: Kappa (K) coefficients were computed as a measure of agreement between intraoperative information/histology and MRI results as well as for interobserver agreement; chi-square and Fisher's exact tests were used to explore the association of the MRI signs with clinical complications. A score was calculated by adding all recorded MRI signs and its predictive ability was tested using receiver operating characteristic (ROC) analysis, against all complications, separately; odds ratios (ORs) for optimal cutoffs were determined with logistic regression analysis. RESULTS: There was excellent agreement (K >0.75, P < 0.001) between MRI and intraoperative findings for invasive placenta, bladder and parametrial involvement. Intraplacental T2 dark bands, myometrial disruption, uterine bulge, and hypervascularity at the utero-placental interface or parametrium, showed significant association (P < 0.005) with poor clinical outcome for both mother and fetus. The MRI score showed significant predictive ability for each adverse maternal event (area under the curve [AUC]: 0.85-0.97, P < 0.001). The presence of ≥3 MRI signs was the cutoff point for a complicated delivery (OR: 19.08, 95% confidence interval [CI]: 6.05-60.13) and ≥6 MRI signs was the cutoff point for massive bleeding (OR: 90.93, 95% CI: 11.3-729.23), hysterectomy (OR: 72.5, 95% CI: 17.9-293.7), or extensive bladder repair (OR: 58.74, 95% CI: 7.35-469.32). The MRI score was not significant for predicting adverse neonatal events including preterm delivery (P = 0.558), low birthweight (P = 0.097), and 5-minute Apgar score (P = 0.078). DATA CONCLUSION: Preoperative identification of specific MRI features may predict peripartum course in high-risk patients for PAS. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;50:602-618.

MRI Features Predictive of Invasive Placenta With Extrauterine Spread in High-Risk Gravid Patients: A Prospective Evaluation.

OBJECTIVE: The objective of our study was to evaluate MRI diagnostic ability in predicting invasive placenta with extrauterine spread in high-risk gravid patients. SUBJECTS AND METHODS: Between March 2016 and June 2017, 49 patients (mean age, 35.7 years; mean gestational age, 32.5 weeks) with sonographically confirmed placenta previa underwent dedicated MRI. All MRI examinations were reviewed by two experienced radiologists prospectively. Intraoperative and pathologic findings were the standard of reference. Kappa values were calculated to assess the agreement between MRI findings and histologic results as well as interrater reliability. ROC curve analysis was used to test the discriminative ability of MRI features for invasive placenta with extrauterine spread. Stepwise multiple logistic regression analysis was performed to identify any MRI findings predictive of invasive placenta and of bladder and parametrial involvement. RESULTS: MRI exhibited significant overall accuracy (AUC = 0.77, p = 0.006) in identifying invasive placenta with 100% sensitivity and negative predictive values; it was highly specific (100%) in identifying placental extension to both bladder and parametrial tissues. Lumpy tapering of the placental edges, intraplacental dark T2 bands, prominent intraplacental vascularity, and serosal hypervascularity were independently associated with an increased risk for invasive placenta. Serosal hypervascularity and vesicouterine space hypervascularity were independent predictors of bladder invasion; abnormal vascularization within the parametrial fat was significant for parametrial invasion. CONCLUSION: MRI is highly accurate in depicting placental extrauterine spread. The presence of abnormal vessels at the uterine serosa was the most important MRI feature for identifying invasive placenta. An abnormal vascular network within the vesicouterine space or parametrium was the most reliable MRI sign for detecting bladder or parametrial involvement.

MRI Assessed Placental Location as a Diagnostic Tool of Placental Invasiveness and Maternal Peripartum Morbidity.

Placenta accreta spectrum (PAS) disorder is one of the leading causes of peripartum maternal morbidity and mortality; its early identification during pregnancy is of utmost importance to ensure the optimal clinical outcome. The aim of the present study is to investigate the possible association of the presence and type/location of placenta previa on MRI with PAS and maternal peripartum outcome. One hundred eighty-nine pregnant women (mean age: 35 years; mean gestational age: 32 weeks) at high risk for PAS underwent a dedicated placental MRI. All women underwent a C-section within 6 weeks from the MRI. All MRIs were evaluated by two experienced genitourinary radiologists for presence, type (complete/partial vs. marginal/low lying), and location (anterior vs. anterior-posterior vs. posterior) of placenta previa. Statistical analysis was performed for possible association of type/location of previa with placental invasiveness and peripartum outcomes. Intraoperative information was used as a reference standard. Complete/partial previa was detected in 143/189 (75.6%) and marginal/low lying previa in 33/189 (17.5%) women; in 88/189 (46.6%) women, the placenta had anterior-posterior, in 54/189 (28.6%) anterior and in 41/189 (21.7%) posterior. Complete/partial previa had an at least 3-fold probability of invasiveness and was more frequently associated with unfavorable peripartum events, including massive intraoperative blood loss or hysterectomy, compared to low-lying/marginal placenta. Posterior placental location was significantly associated with lower rates of PAS and better clinical outcomes. In conclusion, the type and location of placenta previa shown with MRI seems to be associated with severity of complications during delivery and should be carefully studied.

Comparison between 1.5-T and 3.0-T MRI for the diagnosis of placenta accreta spectrum disorders.

PURPOSE: Accurate antenatal diagnosis of placenta accreta spectrum (PAS) is important for optimal management. The purpose of this study was to compare the respective capabilities of 1.5-T and 3.0-T MRI in the diagnosis of PAS. MATERIALS AND METHODS: Between March 2016-March 2021, 190 pregnant women at high risk for PAS underwent dedicated prenatal MRI with either 1.5-T or 3.0-T units at a tertiary imaging center. Cesarian section and MRI were performed less than 6 weeks from each other. Prospectively collected data were evaluated by two experienced genitourinary radiologists for presence and extent of PAS. A comparative study was designed to investigate differences in predictive ability between 1.5-T and 3.0-T MRI groups. Sensitivity, specificity, accuracy, negative and positive prognostic values relative to intraoperative/histological findings, were computed for both groups and were compared with chi-square (χ 2) test. Interobserver agreement was estimated using Kappa test. RESULTS: One hundred-eighty-two gravid women were included in the study; of these, 91/182 (50%) women were evaluated with 1.5-T (mean age, 35 ± 5.1 [SD] years; mean gestational age: 32.5 weeks) and 91/182 (50%) with 3.0-T MRI (mean age, 34.9 ± 4.9 [SD] years; mean gestational age, 32.1 weeks). 1.5-T MRI yielded 95.7% sensitivity (95% CI: 87.8-99.1) and 81.8% specificity (95% CI: 59.8) and 3.0-T MRI 93.8% sensitivity (95% CI: 86.0-97.9) and 83.3% specificity (95% CI: 48.2-97.7) for PAS identification, with no differences between the two groups (P = 0.725 and P >0.999, respectively). MRI showed excellent predictive ability for detecting extrauterine placental spread with 100% sensitivity (95% CI: 89.4-100.0), 96.7% specificity (95% CI: 88.1-99.6) for 1.5-T and 97% sensitivity (95% CI: 84.2-99.9), 96.7% specificity (95% CI: 88.1-99.6) for 3.0-T without differences between the two groups (P > 0.999). Interobserver agreement was excellent for both groups. The most frequently detected MRI signs of PAS for both 1.5-T and 3.0-T groups were placental heterogeneity (n = 85, 93.5% vs. n = 90, 98.9%; P = 0.413), and intraplacental fetal vessels (n = 64, 70.3% vs. n = 65, 71.4%; P = 0.870). CONCLUSION: This study suggests that 3.0-T MRI and 1.5-T MRI are equivalent for the diagnosis of PAS.

Stripped fetal vessel sign: a novel pathological feature of abnormal fetal vasculature in placenta accreta spectrum disorders with MRI correlates.

Abnormal intraplacental hypervascularity is a well-known MRI feature of Placenta Accreta Spectrum (PAS), but the precise nature of these vessels has not yet been specified. Histopathological examination of eleven PAS-hysterectomy specimens and subsequent review of the corresponding MRIs, revealed the presence of large fetal vascular trunks extending deep towards the placental periphery and demonstrating deficient branching along their course ('stripped-fetal-vessel' sign). To our knowledge, this is the first report to describe the pattern of abnormal fetal vasculature in correlation with MRI in PAS.