Montevideo Units (MVU) are a clinical measure used in obstetrics to quantify the strength and frequency of uterine contractions during labor. They were first described by Caldeyro-Barcia and Alvarez in Montevideo, Uruguay, in 1949. MVUs provide a standardized way for clinicians to determine if labor is progressing adequately or if uterine activity is insufficient (hypotonic labor).
How to Calculate MVUs
To calculate MVUs, you need an Intrauterine Pressure Catheter (IUPC) to measure the exact internal pressure of the uterus in millimeters of mercury (mmHg). The calculation is performed over a 10-minute window:
Identify the baseline resting tone (the pressure in the uterus between contractions).
Identify the peak pressure of every contraction within a 10-minute period.
Subtract the baseline tone from each peak pressure to find the intensity of each contraction.
Sum the intensities of all contractions in that 10-minute window.
The Formula: MVU = Σ (Peak Pressure - Baseline Tone) over 10 minutes
Interpreting the Results
MVU Range
Clinical Interpretation
Less than 200 MVUs
Generally considered inadequate for progressive cervical change in the active phase of labor.
200 – 250 MVUs
Considered "adequate" uterine activity for most women to achieve labor progression.
Over 300 MVUs
Hyperstimulation or Tachysystole risk; should be monitored closely for fetal distress.
Example Calculation
Suppose a patient has a baseline resting tone of 10 mmHg. In a 10-minute window, she has four contractions with the following peak pressures:
Contraction 1: 60 mmHg (Intensity: 60 – 10 = 50)
Contraction 2: 55 mmHg (Intensity: 55 – 10 = 45)
Contraction 3: 65 mmHg (Intensity: 65 – 10 = 55)
Contraction 4: 62 mmHg (Intensity: 62 – 10 = 52)
Total MVUs: 50 + 45 + 55 + 52 = 202 MVUs. This would be categorized as adequate uterine activity.
function calculateMVU() {
var baseline = parseFloat(document.getElementById('baselineTone').value);
var p1 = parseFloat(document.getElementById('peak1').value) || 0;
var p2 = parseFloat(document.getElementById('peak2').value) || 0;
var p3 = parseFloat(document.getElementById('peak3').value) || 0;
var p4 = parseFloat(document.getElementById('peak4').value) || 0;
var p5 = parseFloat(document.getElementById('peak5').value) || 0;
var p6 = parseFloat(document.getElementById('peak6').value) || 0;
if (isNaN(baseline)) {
alert("Please enter a valid baseline resting tone.");
return;
}
var peaks = [p1, p2, p3, p4, p5, p6];
var totalMVU = 0;
for (var i = 0; i baseline) {
totalMVU += (peaks[i] – baseline);
} else if (peaks[i] > 0 && peaks[i] <= baseline) {
// Logically a peak can't be lower than baseline if it's a contraction,
// but we won't add negative numbers to the total.
totalMVU += 0;
}
}
var resultArea = document.getElementById('mvu-result-area');
var display = document.getElementById('mvu-total-display');
var interp = document.getElementById('mvu-interpretation-text');
resultArea.style.display = 'block';
display.innerHTML = totalMVU.toFixed(0);
if (totalMVU 200 MVUs).";
interp.style.color = "#e67e22";
} else if (totalMVU >= 200 && totalMVU <= 300) {
interp.innerHTML = "Result: Adequate uterine activity for labor progression.";
interp.style.color = "#27ae60";
} else {
interp.innerHTML = "Result: High uterine activity. Monitor for tachysystole.";
interp.style.color = "#c0392b";
}
}