title: Ultrasonography in pregnancy. ACOG Technical Bulletin Number 187--December 1993.
mesh_terms: D000650:Amnion; D005260:Female; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D012449:Safety; D016216:Ultrasonography, Prenatal / Q000295:instrumentation