Short-term cycles in human fetal activity. I. Normal pregnancies

Recordings of fetal motor activity in utero were carried out on 17 women with normal pregnancies at 23 to 37 weeks' gestation. Fetal motility was monitored by a method based on integrative EMG recordings derived through electrodes attached to maternal abdominal surface. Orthogonal spectral analysis revealed 40 minute and 80 minute cycles in fetal motility in 59% of the fetuses. The correlation between objective and subjective (maternal self-assessment) scores of fetal activity was generally confirmed. Methods of monitoring fetal activity, based on short-term recordings, are criticized in the light of the present results.