Spinal Administration of opioids offers segmental analgesia, but has side effects including pruritus, nausea and vomiting, urinary retention, hypotension, and respiratory depression, both early and delayed. Many Centres in the UK now routinely use supplementation of spinal anaesthesia from bupivacaine with intrathecal fentanyl or diamorphine. If Fentanyl is used, this is usually accompanied by connection to a i.v. Morphine patient-controlled analgesia (PCA)-device in the postoperative period, whereas the use of intrathecal diamorphine seems to result in a reduction in post-operative morphine requirements, which has obviated the need for PCA devices in many centres. There has been recent controversy over which opioid is safer to use with regards to the risk of respiratory depression.1,2 The investigators want to investigate, whether intrathecal diamorphine causes less or more post-operative respiratory depression in healthy mothers undergoing elective caesarean section than intrathecal fentanyl plus post-operative morphine PCA.