Clinical aspects of fetal heart auscultation.

The widespread belief that fetal heart tones are first detected with an unamplified fetoscope at about 20 weeks' gestation has been studied prospectively only twice. Using data collection prospectively from 352 visits of 77 patients between 15 and 23 weeks' pregnancy, we studied various clinical aspects of fetal heart tone detection. We determined the gestational age at the time of initial auscultation of fetal heart tones with an ordinary fetoscope, and its relationship to quickening, parity, and placenta location. Fetal heart tones were first identified by auscultation at a mean gestational age of 19.4 weeks (range 17-22 weeks). Detection was possible in 81% of patients examined at 20 weeks and in virtually all patients examined at 21 weeks or later. Once heard, fetal heart tones were identified in every subsequent visit for all patients. Parity and placenta location were significant factors influencing initial fetal heart tone detection. Auscultation preceded quickening in only 12% of patients. Recommendations for using initial fetal heart tone detection in clinical practice are given.