Fetal heart rate (FHR) monitoring and computer-assisted analysis of FHR patterns were used to study 190 normal pregnancies on one occasion at 20-41 weeks' gestation. The mean baseline FHR decreased, while the overall FHR variation, number of accelerations and time spent in high variation increased with gestation. The time spent in low variation did not change significantly with gestation. These data indicate that, in the interpretation of FHR patterns from high-risk pregnancies, it is necessary to make adjustments for gestational age.