A primigravida at 41 weeks is being augmented with high-dose oxytocin for protracted active phase. An intrauterine pressure catheter shows contractions every 3 minutes, each peaking 45 mmHg above resting tone. Which conclusion is most appropriate?

• A Montevideo units are 135, so contractions are adequate and arrest of dilation should be diagnosed
• B Montevideo units cannot be calculated without knowing the resting tone
• C Montevideo units are 270, so contractions are adequate
• D Montevideo units are 135, so contractions are inadequate and oxytocin should be increased before diagnosing arrest ✓

Explanation

Montevideo units equal the peak contraction amplitude above resting tone multiplied by the number of contractions in a 10-minute period. Here, 45 multiplied by 3 gives 135 MVU, below the threshold of 200 considered adequate for active labor. Arrest diagnoses require adequate contractions first, so oxytocin should be escalated. Option C errs by multiplying incorrectly, and option B is wrong because resting tone is already accounted for when using the amplitude above baseline.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.