title: Fetal heart rates as determined by sonar in early pregnancy.
mesh_terms: D000033:Abortion, Threatened / Q000503:physiopathology; D004452:Echocardiography; D005260:Female; D005318:Fetal Heart / Q000254:growth & development; D005865:Gestational Age; D006339:Heart Rate; D006801:Humans; D011247:Pregnancy