The present study represents the first in a series aimed at examining how individuals monitor maternal-fetal heart rate signals over an extended period of time. Seventy-two undergraduate students monitored simulated maternal-fetal heart rate signals for late decelerations of either high or low amplitude for 48 minutes. The results showed that the ability to detect late decelerations was quite good and did not decline over time. Although the findings regarding detections are encouraging, the participants also made a lot of false alarms. Collectively, these results suggest that the observers still struggled to distinguish critical patterns from the background fetal heart activity.