Strengths and Limitations
In the study, MRI clearly showed the placental morphology, velamentous vessels position and courses of potential vasa previa. That implied the reasons why ultrasonography was unable to reach conclusive diagnosis of vasa previa occasionally. But limited by the low rate of vasa previa cases in pregnancies, the current study is not a large sample randomized controlled trial, so bias can not be fully avoided.
The prevalence rate of vasa previa is relatively low, and ultrasonography is most often used and commonly able to detect the disease. Thus the cases, in which ultrasound cannot reach conclusive diagnosis for vasa previa, will be even fewer. So future long term researches enrolling more additional similar cases are needed to check MRI sensitivity and specificity in this field, though MRI already showed satisfied results in the current study. As MRI is not commonly applied in diagnosing vasa previa, future researches also need strong support from patients, ultrasonology and radiology specialists.