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Five-Tier Fetal Heart Rate Risk Calculator BETA

Fetal heart rate classification and management support

Clinical calculation aid

Five-tier intrapartum fetal heart rate interpretation

Instructions and timing

Assess the current tracing and select the predominant variability, baseline heart rate category, and recurrent deceleration pattern to return the corresponding risk tier, risk of acidemia, risk of evolution, and recommended action.

Timing: Use a current 20-minute tracing segment to determine whether decelerations are recurrent. Do not delay indicated interventions while completing the 20-minute assessment. Continue reassessment after interventions.
Clinical decision support only. Review the complete tracing and clinical circumstances. This tool does not replace bedside assessment, professional judgment, or local protocol.
When more than one finding is present: follow the 2010 priority rules when choosing the pattern entered here: severe overrides moderate or mild; late decelerations override variable decelerations; prolonged decelerations override variable or late decelerations; and minimal or absent variability overrides moderate variability when present for more than 50% of the assessment time.

Pattern inputs

Tap one choice in each section. Use the i button only when you need a definition.

Choose the predominant variability. Use the standard NICHD visual variability category. In the 2010 computer exercise, absent and minimal variability were additionally operationalized numerically for software analysis.
Show variability definitions

Absent: amplitude range is undetectable.

Minimal: detectable amplitude, but 5 bpm or less.

Moderate: amplitude range 6-25 bpm.

Marked: amplitude range greater than 25 bpm.

2010 computer-study note: for automated analysis in that study, absent variability was operationalized as less than 2 bpm amplitude and minimal variability as 2-5 bpm. Those software thresholds are not substituted for the standard visual NICHD definitions in this calculator.

Baseline category lasting more than 10 minutes. The 2010 rule table applies bradycardia severity to a baseline level lasting more than 10 minutes.
Show baseline and bradycardia definitions

NICHD baseline: normal 110-160 bpm; tachycardia is above 160 bpm; bradycardia is below 110 bpm.

2010 Parer-Hamilton wording: severe bradycardia is 70 bpm or less; moderate is described as 70-80 bpm; mild is described as not below 80 bpm, with the baseline level present for more than 10 minutes.

Calculator boundary convention: because the published wording overlaps at 70 and 80 bpm, the selectable bands are made mutually exclusive: mild 81-109 bpm, moderate 71-80 bpm, severe 70 bpm or less. This convention is shown explicitly so the boundary handling is not hidden.

Current 20-min window • recurrent = ≥2 decels and ≥50% of contractions. For recurrent variable or late decelerations, the 2010 rule requires at least 2 decelerations AND decelerations with at least 50% of contractions in a 20-minute window.
Show 2010 deceleration definitions and timing

Recurrence: at least 2 decelerations and at least 50% of contractions have associated decelerations in a 20-minute window.

Variable - severe: recurrent, lasts 1-2 minutes and touches 70 bpm; or lasts more than 2 minutes and touches 80 bpm.

Variable - moderate: recurrent, lasts 30-60 seconds and touches 70 bpm; or lasts more than 60 seconds and touches 80 bpm.

Variable - mild: all else.

Late - severe: recurrent and 45 bpm or more below baseline.

Late - moderate: recurrent and 15-44 bpm below baseline.

Late - mild: recurrent and less than 15 bpm below baseline.

Prolonged: lasts more than 2 but less than 10 minutes. Severe is 70 bpm or less; moderate is down to 70-80 bpm; mild is not below 80 bpm.

Boundary note: the published prolonged-deceleration wording overlaps at 70 and 80 bpm. Apply your institutional convention at the exact boundary values.

Select the pattern, then click Calculate.

EMR / note summary

Important limitations
  • The five-tier color matrix uses the later 2010 Parer-Hamilton Table 1 assignments, with the 2007 Table 2 risk/evolution/action output language.
  • The 2010 operational definitions and priority rules are used for recurrence, deceleration severity, and selection when multiple findings coexist.
  • Recurrent variable or late decelerations require at least 2 decelerations and involvement of at least 50% of contractions in a 20-minute window.
  • The 20-minute window is a classification window, not a required delay before clinically indicated intervention.
  • The NICHD Category I/II/III result is calculated independently from the entered tracing features and is not a conversion of the five-tier color.
  • This tool does not incorporate fetal stimulation response. A failed stimulation response can be a Category II feature and should be considered clinically if testing was performed.
  • Clinical context, uterine activity, stage of labor, response to interventions, and local protocol remain essential.
Sources

Five-tier framework: Tables 2 and 5 adapted and implemented with permission from Parer JT, Ikeda T. A framework for standardized management of intrapartum fetal heart rate patterns. Am J Obstet Gynecol. 2007;197:26.e1-26.e6. Tables 1 and 2 adapted and implemented with permission from Parer JT, Hamilton EF. Comparison of 5 experts and computer analysis in rule-based fetal heart rate interpretation. Am J Obstet Gynecol. 2010;203.

NICHD 3-tier result: based on the 2008 NICHD Workshop standardized FHR interpretation system (Macones GA, Hankins GDV, Spong CY, Hauth J, Moore T. Obstet Gynecol. 2008;112:661-666).

This calculator is an independent Perinatology.com implementation. No endorsement by the authors, journals, publishers, or NICHD is implied.