Ultrasonography in threatened abortion.
D000022:Abortion, Spontaneous / Q000453:epidemiology; D000033:Abortion, Threatened / Q000175:diagnosis*; D010064:Embryo Implantation; D005260:Female; D006801:Humans; D010923:Placenta Previa / Q000453:epidemiology; D011247:Pregnancy; D014463:Ultrasonography