18 healthy parturients were monitored during normal labor in order to determine the influence of uterine contractions and fetal body movements on fetal heart rate beat-to-beat variability (BTBV). The BTBV was 5.37 +/- 1.28 during the baseline period and a significant increase to 6.46 +/- 1.64 was found during uterine contractions (p less than 0.001). The BTBV during fetal movements, 6.21 +/- 2.29, did not differ significantly from the value of the baseline period.