How to Calculate Montevideo Units

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What are Montevideo Units (MVUs)?

Montevideo Units (MVUs) are a clinical measure used in obstetrics to quantify the strength and frequency of uterine contractions during labor. Developed in 1949 by Roberto Caldeyro-Barcia and Hermógenes Alvarez in Montevideo, Uruguay, this metric helps clinicians determine if labor is progressing adequately or if intervention (like Pitocin) is necessary.

The Formula for MVUs

To calculate MVUs, you must have an Internal Uterine Pressure Catheter (IUPC) in place to get accurate pressure readings. The formula is:

MVUs = (Average Peak Pressure – Resting Tone) × Number of Contractions in 10 Minutes

Alternatively, it is the sum of the intensities of all contractions occurring within a 10-minute window. Intensity is defined as the peak pressure of a contraction minus the baseline resting tone of the uterus.

Interpreting the Results

Once you calculate the total Montevideo Units, the following thresholds are generally used in clinical practice:

• Less than 200 MVUs: Often considered inadequate for significant cervical change in the active phase of labor.
• 200 – 250 MVUs: Generally considered the "gold standard" for adequate labor.
• Greater than 250 MVUs: Indicates strong uterine activity. Excessively high MVUs may lead to uterine tachysystole or fetal distress.

Calculation Example

Suppose a patient has 4 contractions in a 10-minute period. The peak pressures of these contractions average 65 mmHg, and the resting tone (baseline) is 15 mmHg.

1. Subtract the resting tone from the average peak: 65 – 15 = 50 mmHg (Intensity).
2. Multiply by the number of contractions: 50 × 4 = 200 MVUs.

In this scenario, the patient is reaching the threshold for adequate labor activity.

function calculateMVU() { var count = document.getElementById('contractionCount').value; var peak = document.getElementById('avgPeak').value; var baseline = document.getElementById('restingTone').value; var resultDiv = document.getElementById('mvuResult'); if (count === "" || peak === "" || baseline === "") { resultDiv.style.display = "block"; resultDiv.style.backgroundColor = "#fff3cd"; resultDiv.style.color = "#856404"; resultDiv.innerHTML = "Please fill in all fields."; return; } var countVal = parseFloat(count); var peakVal = parseFloat(peak); var baselineVal = parseFloat(baseline); if (peakVal <= baselineVal) { resultDiv.style.display = "block"; resultDiv.style.backgroundColor = "#f8d7da"; resultDiv.style.color = "#721c24"; resultDiv.innerHTML = "Error: Peak pressure must be higher than the resting tone."; return; } var intensity = peakVal – baselineVal; var mvu = intensity * countVal; var interpretation = ""; var bgColor = ""; var textColor = ""; if (mvu < 200) { interpretation = "Inadequate Labor Activity (= 200 && mvu 250 MVUs)"; bgColor = "#d1ecf1"; textColor = "#0c5460"; } resultDiv.style.display = "block"; resultDiv.style.backgroundColor = bgColor; resultDiv.style.color = textColor; resultDiv.innerHTML = "

Total: " + mvu.toFixed(0) + " MVUs

" + interpretation + "

"; }