μ-opioid receptor genetic polymorphisms and duration of epidural fentanyl analgesia during early labor.

Background: Epidural fentanyl is commonly used for initiation of early labor analgesia. The aim of this prospective study is to test the hypothesis that duration of epidural fentanyl analgesia differs in nulliparous women requesting epidural analgesia in early labor who are variant allele carriers of the OPRM1 SNVs 118A>G rs1799971, IVS2+31G>A rs9479757, and IVS2+691G>C rs2075572.

Methods: Two hundred and twenty parturients who received epidural analgesia with fentanyl were included in the 118A>G analysis, and a 196 sub-cohort was included in the IVS2+31G>A and IVS2+691G>C exploratory analysis.