2Parvey HR, Dubinsky TJ, Johnston DA, et al. The chorionic rim and low-impedance intrauterine arterial flow in the diagnosis of early intrauterine pregnancy : evaluation of efficacy [ J ]. AJR,1996, 167(DEC) : 1479-1485.
3Di Luigi G,Patacchiola F,La Posta V,et al.Early ovarian pregnancy diagnosed by ultrasound and successfully treated with multidose methotrexate.A case report.Clinical and experimental obstetrics and gynecology,2012,39(3):390-393.
4Alcazar JL,Ortiz CA.Transvaginal color Doppler ultrasonography in the management of first-trimester spontaneous abortion..European Journal of Obstetrics.Gynecology and Reproductive Biology,2002,102(1):83-87.
5V C Y Lee,T W Y Yeung,O S Tang,et al.Effect of letrozole on uterine artery Doppler flow indices prior to first-trimester termination of pregnancy:a randomized controlled trial.Ultrasound in obstetrics& gynecology,2012,40(4):392-397.
6Ultrasound may be required before abortion in Virginia.New scientist,2012,213(2853):1-1.
7Tzeng CE,Hwang JL,Au HK,et al.Sonographic patterns of the endometrium in assessment of medical abortion outcomes[J]. Contraception, 2013,880 ): 153-159.
8Di Luigi G, Patacchiola F, La Posta V, et al. Early ovarian pregnancy diagnosed by ultrasound and successfully treated with multidose methotrexate. A case report[J]. Clin Exp Obstet Gynecol, 2012, 39(3): 390-393.