Internal tocography in a nullipara in the active phase shows 4 contractions in 10 minutes, each peaking 50 mm Hg above the resting tone. Calculate the Montevideo units and state whether uterine activity is adequate.

• A 100 MVU, inadequate
• B 200 MVU, adequate ✓
• C 250 MVU, excessive
• D 50 MVU, inadequate

Explanation

Montevideo units equal the amplitude of each contraction (peak intensity minus resting tone) multiplied by the number of contractions in 10 minutes. Here 50 mm Hg times 4 contractions equals 200 MVU, the threshold generally accepted as adequate for active-phase progress. Values below about 200 MVU suggest inadequate contractile force and support oxytocin augmentation rather than a diagnosis of cephalopelvic disproportion.

Reference: Williams Obstetrics, 26th ed.

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