Optimum Length of Catheter in the Epidural Space for Labor Analgesia in Non-obese Women: a Randomised Controlled Trial of 4 cm Versus 5 cm

Epidural analgesia was introduced to the world of obstetrics in 1909 by Walter Stoeckel. Over the following 100 years it has developed to become the gold-standard for delivery of intra-partum analgesia, with between 60 and 75% of North American parturients receiving an epidural during their labor. Effective labor analgesia has been shown to improve maternal and fetal outcomes. One aspect of catheter insertion that has not been fully evaluated, and with very little recent work undertaken, is the optimal length of epidural catheter to be left in the epidural space. Dislodgement or displacement of epidural catheter remains a significant cause for failure with analgesia. Novel methods of fixation may further reduce the risk of catheter migration. Another factor is the direction of travel within the epidural space, only 13% of lumbar catheters remain uncoiled after insertion of more than 4 cm into the epidural space. Hypothesis: The investigators hypothesize that catheters inserted to 4 cm will have a lower rate of failure when compared to those inserted to 5 cm. Objective: This study aims to evaluate the difference in quality of labor analgesia delivered by epidural catheters inserted to either 4 or 5 cm into the epidural space. This study will be conducted as an interventional double-blinded randomised control trial to establish best practice.