DefinePK

Abstract

Introduction


Placenta previa is the placenta, implanted entirely or in part in the lower uterine segment. Most important in diagnosis is the distinction between major and minor degree placenta previa. The causes of placenta previa are frequently unclear. The most identifiable etiological factor is previous uterine damage. 1 Transabdominal, transvaginal and transperineal ultrasound has been used to localize the placenta with variable success rate. 2-4 Sonographic diagnosis of placenta previa has an excellent record of accuracy and safety. 5 Transvaginal ultrasound utilizes higher frequencies of ultrasound and provides a better resolution of lower edge of placenta. It is the most accurate method for diagnosis and localizing placenta previa. 6 The source of diagnosis and management difficulty is "rising placenta". Although around 5% of women have ultrasound evidence of low placenta at 20 weeks, only 10% of this 5% (i.e. 0.5% overall) actually have a placenta previa at delivery. 7 The apparent change of placental position results from formation of lower uterine segment. Placenta previa appears to migrate to a more fundal position in advancing pregnancy due to more rapid growth of lower uterine segment. Furthermore, this phenomenon is more pronounced in the anterior than in the posterior low lying placenta. 8-10 The present study was conducted to evaluate the role of ultrasound in diagnosing placental migration in the second half of the pregnancy and deciding for mode of delivery in diagnosed cases of placenta previa.