Contraction Frequency Calculator

Actual sequential onset-to-onset contraction intervals, not contraction duration, clinical labour diagnosis, labour stage or instruction to delay care.

Description

Contraction onset intervals measure the gaps between successive recorded starts.

Contraction onset intervals measure the gaps between successive recorded starts.^[1]

Mean interval differs from contraction duration and from a count in a fixed window.

When to use Contraction Frequency Calculator

Use this tool to calculate or review the supplied observations under the stated rules. Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.

How to use Contraction Frequency Calculator and understand its results

Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
Enter independentlyRecordedContractionOnsetsMinutes, using the field meanings and rules below, then run the tool.
Read result.observedOnsetIntervalsMinutes, result.observedMeanOnsetIntervalMinutes. Use the units and sign conventions below.
Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.

Input field	Meaning	Value type	Requirement
independentlyRecordedContractionOnsetsMinutes	Independently recorded contraction onsets minutes	list of number	Required

Require at least two strictly increasing finite contraction-onset minute coordinates. Return adjacent onset differences and their arithmetic mean. No positivity requirement applies to the coordinates themselves and no event count per fixed period is inferred.

gap_i=onset_(i+1)−onset_i; meanInterval=mean(gaps)

Use the matching field units and the exact boundary, ordering and reference rules above.

Output field	Meaning	Value type
result	Structured result; its nested fields below contain the actual calculation or selected reference	object
result.observedOnsetIntervalsMinutes	Observed Onset Intervals Minutes	list
result.observedMeanOnsetIntervalMinutes	Observed Mean Onset Interval Minutes	number

json

{
  "input": {
    "independentlyRecordedContractionOnsetsMinutes": [
      0,
      5,
      11
    ]
  },
  "output": {
    "result": {
      "observedOnsetIntervalsMinutes": [
        5,
        6
      ],
      "observedMeanOnsetIntervalMinutes": 5.5
    }
  }
}

Limitations and assumptions

Dating evidence, acquisition conditions and applicable clinical references remain independently established. The output describes supplied observations or a conditional model without diagnosing an outcome, choosing a dose or verifying clinical applicability.

Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Lists and matrices must be dense, without missing cells. Numeric lists allow at most 10000 entries; ordinary string lists allow at most 128 strings of 128 UTF-16 units each; numeric matrices allow at most 128 rows and 128 columns, subject to narrower requirements above. Extremely large composite outputs are rejected.

Alternative or Complementary methods

For a related step, use Total Labor Duration Calculator: Total labor duration requires independently established onset and endpoint boundaries. For a complementary comparison, use Second Stage Labor Duration Calculator: Second-stage labor duration depends on independently identified stage boundaries.

References

Contraction Frequency Calculator — tool.io

Similar or alternative tools

Total Labor Duration Calculator
Total labor duration requires independently established onset and endpoint boundaries.
Second Stage Labor Duration Calculator
Second-stage labor duration depends on independently identified stage boundaries.