Objective: This study was undertaken to determine whether external stimulation using a halogen light source influences fetal heart rate (FHR) responsiveness and nonstress test results.
Study design: A total of 107 patients at 32 to 42 weeks' gestation undergoing a nonstress test were randomly assigned to have either transabdominal light stimulation or no light stimulation. The light (Vector Compact Sport Spot, Ft Lauderdale, Fla) was turned on for 10 seconds. If no qualifying FHR acceleration was observed, then the stimulus was repeated at 10-minute intervals for a maximum of 3 times. The investigators were blinded as to light stimulation for FHR interpretation.
Results: Reactive results were present in 52 cases in each group. Light stimulation led to a significantly shorter time (P <.02) until the first FHR acceleration (difference: 2.1 minutes; 95% CI 0.4-3.8 minutes). The height and width of the first acceleration were indistinguishable between groups. The time until a reactive result was significantly shorter after light stimulation (difference: 4.2 minutes; 95% CI 2.0-6.4 minutes).
Conclusion: The earlier onset of FHR accelerations after halogen light stimulation prompted a more rapid reactive nonstress test result.