The clustering of fetal heart rate changes and fetal movements in pregnancies between 20 and 30 weeks of gestation.

The temporal organization (nonrandomness) of fetal heart rate (FHR), fetal movement, and their association was evaluated in 20 normal pregnancies at 20 to 22 or 28 to 30 weeks of gestation with the use of external electronic fetal monitoring and statistical analysis with the runs test. At 20 to 22 weeks, significant clustering was found in one of 10 pregnancies for FHR change, two of 10 pregnancies for fetal movement, and one of 10 pregnancies for FHR changes associated with fetal movement. At 28 to 30 weeks, significant clustering was found in eight of 10 pregnancies for FHR change, eight of 10 pregnancies for fetal movement, and all 10 pregnancies of FHR change associated with fetal movement. There was significantly more clustering of FHR change, fetal movement, and FHR change associated with fetal movement at 28 to 30 weeks of gestation than at 20 to 22 weeks of gestation. Clustering of FHR changes was highly correlated with clustering of fetal movement.