The Three Tier Fetal Heart Rate Interpretation System

In 2008, the National Institute of Child Health and Human Development, or NICHD, suggested a three-tiered system and developed specific definitions and terminology to be used for the interpretation of FHR patterns.  This was in an effort to standardize terminology used across the country and improve communication between providers.

Category 1

Category 1 tracings include all of the following:

Baseline heart rate of 110-160

Baseline FHR variability is moderate

No late or variable decelerations

Early decelerations may be present or absent

Accelerations may be present or absent

Category 2

Category 2 tracings inlude all tracings that are not Category 1 or Category 3.  The majority of FHR tracings in active labor will be included in Category 2.  These may include but are not limited to:

Bradycardia not accompanied by absent variability

Tachycardia

Minimal variability

Absent variability with no decelerations

Marked variability

Absence of accelerations with stimulation

Periodic or episodic decelerations with minimal or moderate variability

Prolonged decelerations

Category 3

Category 3 tracings include either

Absent variability and any of the following:

• Recurrent late decelerations
• Recurrent variable decelerations
• Bradycardia

Sinusoidal pattern

Some interesting statistics

In a study done on 48,444 laboring women by Jackson, et. al., in 2011.

• 99% of women had Category 1 FHR tracings at least part of their labor.
• 86% of women had at least some segments of a Category 2 FHR tracing at some time during their labor.
• only 0.1% of women had a category 3 tracing

References:

Jackson, M., Holmgren, C. M., Esplin, M.S., Henry, E., & Varner, M.W. (2011). Frequency of fetal 

heart rate categories and short-term neonatal outcome. Obstetrics and Gynecology, 118(4), 803-808.

Lyndon, A., Ali, L. U. (2015). Fetal heart monitoring: Principles and practices. Dubuque, IA. Kendall Hunt Professional.