title: Comparison of spontaneous contraction rates of in situ and isolated fetal hearts in early pregnancy.
mesh_terms: D005260:Female; D005318:Fetal Heart / Q000502:physiology*; D005865:Gestational Age; D006339:Heart Rate; D006801:Humans; D011247:Pregnancy; D013696:Temperature; D013997:Time Factors; D014465:Ultrasonics