Emerging Role of Prenatal Magnetic Resonance Imaging in the Diagnosis of Placental Adhesion Disorders and its Relation with Intraoperative Findings- A Cross-sectional Study

Placental Adhesion Disorders (PADs) aka Placenta Accreta Spectrum (PAS) of disorders are a common cause of postpartum haemorrhage, which in turn is an avoidable cause of significant maternal morbidity and mortality. The exponential increase in the prevalence of PADs worldwide primarily ascribed to increasing percentage of caesarean section deliveries therefore contributes significantly to potentially life-threatening obstetrical emergencies. Accurate prenatal diagnosis of PAD is hence fundamental for patient management and prognostication. Imaging plays an indispensable role in the antenatal diagnosis of PAD thereby translating to improved maternal outcomes. Aim: To determine the diagnostic accuracy of prenatal Magnetic Resonance Imaging (MRI) in predicting abnormal invasive placentation and to associate MRI findings with intraoperative findings. Materials and Methods: The present cross-sectional study was conducted between March 2019 to March 2020. Pregnant females with clinically and/or sonographically suspected PAD and having major risk factors of PAD {Lower Segment Caesarean Section (LSCS) in previous and placenta previa in present gestation} were subjected to dedicated placenta protocol MRI examination. The placental morphology, localisation and adhesion suggestive features were evaluated in detail. Descriptive statistical analysis was done for final assessment. Results: A total of 27 study participants, with mean age of 28±2.15 years, showed MRI findings compatible with PAD. Placenta previa complete (66.67%); was the dominant subtype observed in the study. In terms of degree of invasion, placenta accreta in 44.44% (n=12) was predominantly observed on preliminary MRI based assessment. The most reliable MRI features predictive of placental invasion in the present study (seen in 100% cases of PAD) included T2 dark intraplacental bands, heterogenous intraplacental signal intensity, disorganised intraplacental vascularity, myometrial thinning, loss of the uteroplacental interface and maternal neovascularity. In one case, MRI erroneously over-diagnosed increta as percreta. The overall diagnostic performance of these MRI parameters was with sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of 100%, 95%; 87.5% and 100% in those with placenta percreta compared to 94.12%, 100.00%, 100% and 95% for the placenta accreta or increta cases, respectively. Conclusion: MRI has high diagnostic accuracy in detection of PADs among the high-risk patients. Dedicated placenta protocol prenatal MRI should hence be incorporated in diagnostic work- up of all high-risk patients of PAD for reaping benefits of timely management, planning and saving lives.