A rise in pain threshold during labor: a prospective clinical trial.

To evaluate changes in pain threshold before, during and after labor in a prospective clinical trial. Forty pregnant women at term were included. Pain threshold in 18 specific pressure points was evaluated using a dolorimeter. Woman underwent pain threshold assessment at term before labor, during the active phase of labor and postpartum. Subjective pain intensity was assessed by the parturient using the Verbal Rating Scale (VRS). Pain threshold was significantly higher during active phase of labor. There was a significant decline in pain threshold after labor as compared to pain threshold during labor (2.507+/-0.947 and 2.608+/-1.023, respectively, p=0.01). Pain intensity using the VRS score was higher during labor than before labor (4.8+/-2.7 and 2.4+/-2.6 p<0.001). We found a significant rise in pain threshold during labor in term pregnancies. This rise may have an intended protective effect during the intense labor pain experience.