Studies of antepartum behavioral state in the human fetus at term

This prospective study describes intrauterine behavioral states in the human fetus. The variables used are fetal movement and two expressions of fetal heart rate (FHR): long-term variability and baseline rate. Fetal movement was recorded with the use of two strain gauges. FHR was measured with a transabdominal fetal electrocardiographic processor. Sixteen fetuses of normal pregnant patients were studied near term. One-minute periods called “epochs” were classified as quiet, active, and intermediate, based on the presence or absence of fetal movement (longer in duration than one second), increased or decreased long-term FHR variability, and the baseline of the FHR. Complete agreement in epoch classification was noted in 79.3 per cent of the 2,054 epochs analyzed. Quiet and active one-minute epochs were clustered into longer time periods representing quiet and active fetal behavior states similar to those seen in the neonate. The overall visual evaluation of the tracings based on the above noted criteria demonstrated the presence of quiet, active, and transitional states in the fetus. Mean duration of a complete cycle, including the quiet, active, and transitional states, was 62.3 minutes. The mean duration in the quiet state was 22.8 minutes and the mean duration in the nonquiet states (active and transitional) was 39.5 minutes. The significance of these intrauterine behavioral states is stressed.