Localization of the placenta has always been one of the major applications of diagnostic ultrasound (Gottesfeld et al. 1966; Kratochwil 1967). From its inception, sonography consistently proved superior to X-ray placentography, angiography, thermography, and isotope scanning for evaluations of the placenta. With the advent of grayscale imaging, ultrasound was able to resolve structural differences in placentas and relate them to pathoanatomic changes (maturity grades, etc.). Sharper resolution also enabled early identification of the villous chorion frondosum and its differentiation from the chorion laeve.
KeywordsPlacenta Previa Cervical Canal Transabdominal Sonography Maturity Grade Lower Uterine Segment
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