Application of Indirect Signs of Magnetic Resonance Imaging (MRI) in Prenatal Diagnosis of Abnormally Invasive Placenta

Diagnostic Accuracy of Magnetic Resonance Imaging in the Diagnosis of Placenta Accreta Spectrum: A Systematic Review and Meta-analysis

Objective:

To evaluate the diagnostic accuracy of magnetic resonance imaging (MRI) in diagnosing placenta accreta spectrum (PAS).

Methods:

We conducted a comprehensive literature search from database inception to November 2023 using terms such as placenta creta, increta, percreta, PAS, MRI, and their respective Medical Subject Headings terms. All prospective and retrospective cohort, case-control, and cross-sectional studies involving prenatal magnetic resonance imaging diagnosis of PAS with subsequent pathological confirmation were included.

Results:

A total of 40 studies encompassing 3664 women met the inclusion criteria, with 1894 cases confirmed pathologically as PAS. The overall sensitivity of MRI was 0.867 (95% confidence interval (CI): 0.807–0.910), and the specificity was 0.860 (95% CI: 0.799–0.905), with a correlation of 0.693 between sensitivity and specificity. The estimated odds ratio was 28.693 (95% CI: 14.463–56.924), the negative likelihood ratio was 0.178 (95% CI: 0.122–0.258), and the positive likelihood ratio was 4.316 (95% CI: 3.186–5.846). Analysis of individual MRI criteria revealed estimates of sensitivity, specificity, odds ratio, negative likelihood ratio, and positive likelihood ratio for abnormal placental bed vascularization as 0.500, 0.740, 2.788, 0.571, and 1.645 respectively; 0.384, 0.985, 6.270, 0.471, and 2.720 for bladder wall interruption; 0.766, 0.818, 13.638, 0.262, and 3.375 for the presence of dark intraplacental bands; 0.691, 0.913, 10.828, 0.352, and 3.361 for heterogeneous placenta; 0.688, 0.984, 34.886, 0.254, and 7.164 for indistinctive myometrium; 0.757, 0.864, 8.496, 0.362, and 2.778 for loss of retroplacental dark zone; 0.828, 0.593, 5.829, 0.329, and 1.766 for myometrial thinning; and 0.518, 0.916, 9.473, 0.411, and 3.526 for placental bulge, respectively.

Conclusion:

MRI demonstrates significant utility in diagnosing PAS and its severity. It is recommended for use in all cases with inconclusive ultrasonographic findings.

Registration:

Registration number CRD42021267501.

Development and validation of MRI-based scoring models for predicting placental invasiveness in high-risk women for placenta accreta spectrum

OBJECTIVES

To develop and validate MRI-based scoring models for predicting placenta accreta spectrum (PAS) invasiveness.

MATERIALS AND METHODS

This retrospective study comprised a derivation cohort and a validation cohort. The derivation cohort came from a systematic review of published studies evaluating the diagnostic performance of MRI signs for PAS and/or placenta percreta in high-risk women. The significant signs were identified and used to develop prediction models for PAS and placenta percreta. Between 2016 and 2021, consecutive high-risk pregnant women for PAS who underwent placental MRI constituted the validation cohort. Two radiologists independently evaluated the MRI signs. The reference standard was intraoperative and pathologic findings. The predictive ability of MRI-based models was evaluated using the area under the curve (AUC).

RESULTS

The derivation cohort included 26 studies involving 2568 women and the validation cohort consisted of 294 women with PAS diagnosed in 258 women (88%). Quantitative meta-analysis revealed that T2-dark bands, placental/uterine bulge, loss of T2 hypointense interface, bladder wall interruption, placental heterogeneity, and abnormal intraplacental vascularity were associated with both PAS and placenta percreta, and myometrial thinning and focal exophytic mass were exclusively associated with PAS. The PAS model was validated with an AUC of 0.90 (95% CI: 0.86, 0.93) for predicting PAS and 0.85 (95% CI: 0.79, 0.90) for adverse peripartum outcome; the placenta percreta model showed an AUC of 0.92 (95% CI: 0.86, 0.98) for predicting placenta percreta.

CONCLUSION

MRI-based scoring models established based on quantitative meta-analysis can accurately predict PAS, placenta percreta, and adverse peripartum outcome.

CLINICAL RELEVANCE STATEMENT

These proposed MRI-based scoring models could help accurately predict PAS invasiveness and provide evidence-based risk stratification in the management of high-risk pregnant women for PAS.

KEY POINTS

• Accurately identifying placenta accreta spectrum (PAS) and assessing its invasiveness depending solely on individual MRI signs remained challenging. • MRI-based scoring models, established through quantitative meta-analysis of multiple MRI signs, offered the potential to predict PAS invasiveness in high-risk pregnant women. • These MRI-based models allowed for evidence-based risk stratification in the management of pregnancies suspected of having PAS.

Comparison of Magnetic Resonance Imaging of the Lower Uterine Segment in Pregnant Women with Central Placenta Previa with and without Placenta Accreta Spectrum from a Single Center

BACKGROUND Placenta accreta spectrum (PAS) includes placenta increta, placenta percreta, and placenta accreta. PAS is due to abnormal decidualization and can lead to severe maternal hemorrhage and occurs in up to 3% of women with central placental previa (CPP). This study from a single center aimed to compare the magnetic resonance imaging (MRI) changes in the lower uterine segment in pregnant women with CPP, with and without PAS. MATERIAL AND METHODS This retrospective study includes 90 pregnant women with PAS and 66 pregnant women without PAS. All participants were confirmed to have CPP by MRI. Eight MRI parameters were assessed and compared with perinatal outcomes for mothers and newborns. RESULTS The pregnancies in the non-PAS group had less operative time (P=0.001), less intrapartum hemorrhage (P<0.001), and less blood transfusion than the PAS group (P<0.001). The 8 MRI variables with different odds ratios were placenta thickness (4.20), cervical lengths (3.27), placental dark T2 bands area (5.10), cervical marginal sinus (3.04), bladder bulge (3.55), myometrial thinning (6.41), lower uterine segment bulge (4.61), and placental signals in the cervix (9.14). The sensitivity and specificity of MRI in the diagnosis of PAS were 82.22% and 91.09%, respectively, by the combined 8 MRI features, and the area under the curve (AUC) was 0.816. CONCLUSIONS The findings from this study showed that MRI of the lower uterine segment had high sensitivity and specificity for the diagnosis of PAS in pregnant women with CPP.