Sensory thresholds during the antepartum, intrapartum and postpartum periods

The present exploratory study measured pain and tactile thresholds in response to mechanical stimulation of the hand before labor, during labor, and after parturition in women. In women who had Lamaze childbirth preparation (but not in women who did not have childbirth preparation), pain thresholds were significantly higher during labor (determined up to 8 cm cervical dilatation) than prior to labor and 24 hours postpartum. Tactile thresholds did not change during any of these conditions. These findings support earlier findings in this laboratory that vaginocervical mechanostimulation elevated pain thresholds in human and animal subjects, and more recent findings that pain thresholds increased in rats during delivery of individual young. The present findings suggest that an endogenous process that attenuates the pain of parturition is activated when the cervix dilates during labor.