Psychophysical correlates of labor pain intensity and unpleasantness

The neurobiological mechanisms linking perinatal pain and mood disorders remain unclear. Emotional dimensions of labor pain, particularly unpleasantness, may reflect engagement of limbic pathways shared with affective disorders. This study examined whether prenatal quantitative sensory testing (QST) parameters are associated with the sensory and emotional dimensions of labor pain. Healthy primiparous women were enrolled and followed from third trimester through delivery. Prenatal QST assessed mechanical and thermal thresholds, tolerances, and temporal summation. Labor pain was recorded hourly using a validated electronic diary. Univariable linear regression evaluated relationships between QST measures and labor pain outcomes. Of 164 participants completing QST, , 55 had complete labor pain diaries. Prenatal QST parameters were associated with emotional, but not sensory, aspects of labor pain. Pain unpleasantness was associated with average heat threshold (Coefficient = 40.3, SE = 17.2, p = 0.02), post wind-up pain (Coefficient = -48.9, SE = 25.3, p = 0.06) and post probe pain (Coefficient = -52.7, SE = 26.8, p = 0.06), using a p < 0.1 threshold to identify associations. Although exploratory, these findings suggest that prenatal QST, particularly thermal threshold and central sensitization measures, may help identify individuals at risk for maladaptive labor pain and postpartum mood disorders.