The role of arginine vasopressin in human labour: functional studies, fetal production and localisation of V1a receptor mRNA

Objective To investigate labour‐associated changes in: 1. the myometrial contractile response to arginine vasopressin compared with oxytocin in vitro 2. fetal production of arginine vasopressin and 3. myometrial vasopressin V1a receptor mRNA. Design The contractile response to vasopressin (compared with oxytocin) was investigated in paired myometrial strips in vitro. Blood was taken from the umbilical artery and vein at delivery and arginine vasopressin measured by radio‐immunoassay. V1a receptor mRNA was determined by in situ hybridisation. Results Myometrium was more sensitive to arginine vasopressin than oxytocin (P