Study observation:Find:Pt:Yolk sac^Fetus:Nom:US
study observation:find:pt:yolk sac^fetus:nom:us
Study observation:Finding:To identify measures at a point in time:Yolk sac^Fetus:Nominal:Ultrasound
study observation:finding:to identify measures at a point in time:yolk sac^fetus:nominal:ultrasound