This HD video explains the causes and pathophysiology of sinusoidal pattern on electronic fetal heart rate monitoring.
NST Explained:    • Nonstress Test Explained  
Baseline FHR explained:    • Baseline FHR explained  
FHR Baseline Variability Explained:    • FHR Baseline Variability Explained  
FHR Decelerations:    • FHR Decelerations Explained  
Periodic Accelerations Explained:    • Periodic accelerations explained