Randomised double-blind comparison of obstetric outcome after epidural labour analgesia using ropivacaine or bupivacaine

The provision of analgesia to labouring women is a fundamental aspect of obstetric care and an essential function of a modern hospital obstetric unit. However, it is important to minimise any detrimental effects that the methods used may have on obstetric outcome. Of the methods currently available to treat labour pain, epidural analgesia remains by far the most effective. However, audit data in Hong Kong have revealed a high incidence of instrumental delivery and Caesarean section in patients who have epidural labour analgesia. The reasons for this are undetermined. Methods of optimising obstetric outcome after epidural analgesia are controversial. Recently, there has been a move toward the use of very low concentrations of local anaesthetics combined with a lipophilic opioid such as fentanyl. However, motor block can still occur, even with low concentrations. We hypothesised that it might be possible to improve outcome by using a local anaesthetic drug with a high sensory:motor differential block ratio, such as ropivacaine, which was introduced into Hong Kong at the time of the design of this study.