Baseline fetal heart rate (FHR): Average FHR over two contraction cycles or 10 minutes

Baseline changes: Fluctuations in FHR unrelated to uterine contractions

Periodic changes: Fluctuations in FHR related to uterine contractions

Amplitude: Difference in beats per minute between baseline readings and fluctuations in FHR

Recovery time: Difference between the end of the contraction and the return to baseline FHR

Acceleration: Transient rise in FHR lasting longer than 15 seconds and associated with a uterine contraction

Deceleration: Transient fall in FHR related to a uterine contraction

Lag time: Difference between the peak of the contraction and the lowest point of deceleration