28. Dysfunctional labor (functional dystocia). Medicines that influence uterine contractility
Covers functional dystocia, the uterine-power causes of slow or difficult labour, starting with normal contraction patterns and how strength is measured in Montevideo units. Types of dysfunctional labour are set out in a table with features and management, followed by criteria for slow progress in the active phase, arrest and the second stage. A second table groups medicines acting on the uterus, including uterotonics and tocolytics, with their uses and cautions, and a closing warning about excluding obstruction before giving oxytocin.
Topic 28 of 61 in the MU Sofia syllabus for Obstetrics and Gynecology (Medicine, Year 5). The free AceMed note covers it in 4 sections, about 144 words (2 min of reading), with 16 flashcards.
In this note
Introduction
Normal uterine activity
Types of dysfunctional labour
Medicines that act on the uterus
Introduction
Dystocia means difficult or slow labour. It is caused by problems with the powers (uterine contractions), the passenger (fetus) or the passage (pelvis and soft tissues). This topic covers the powers: functional dystocia.
Normal uterine activity
In active labour contractions come 3–5 every 10 minutes, last 40–60 seconds, and spread from the fundus downwards (fundal dominance). Their strength is measured in Montevideo units (intensity × number in 10 min); about 200 or more is adequate.
Types of dysfunctional labour
Slow progress
Active phase: dilatation < 2 cm in 4 hours (or the partogram crossing the action line) = delay.
Arrest: no change for 4 hours or more with adequate contractions (or 6 hours with oxytocin).
Second stage: delay if no delivery after 2–3 hours of active pushing in a first labour.
Medicines that act on the uterus
Before giving oxytocin for slow labour, always exclude obstruction (cephalopelvic disproportion or malposition): stimulating an obstructed uterus can rupture it.
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