The most accurate and precise measure of uterine tone is unknown. The most commonly described in vivo method in the literature is a qualitative numeric scoring scale from 0-10. The 0-10 uterine tone score has demonstrated good and excellent inter-rater reliability between 1 and 2 raters respectively, and good inter-rater agreement. Recent data suggests that the 0-10 uterine tone score is well-correlated with clinical assessments of uterine tone.
A handful of studies have used a quantitative "hardness meter", including a Shore durometer, to describe uterine tone in vivo, with promising results. The instrument has not yet been validated in cesarean delivery.
