4Kabil Kueur S, Temizkan O, Afis A, et al. Role of endometrialpower Doppler ultrasound using the international endometrial tumor analysis group classification in predicting intrauterine pathology[J]. Arch Gynecol Obstet, 2013, 3(4): 1123- 1126.
5周永昌,郭万学.超声医学[M].下册,第4版,北京:科学技术文献出版社,2002:1422.
6Quant HS, Friedman AM, Wang E, et al. Transabdominal uhrasonography as a screening test for second-trimester placenta previa[J]. Obstetrics & Gynecology, 2014, 123(3): 628-633.
7Stafford IA, Dashe JS, Shivvers SA, et al. Ultrasonographic cervical length and risk of hemorrhage in pregnancies with placenta previa [J]. Obstetrics & Gynecology, 2010, 116 (3): 595-600.