Nitrous oxide in obstetric and gynaecological practice

Nitrous oxide (N2O) has been used for obstetric analgesia for over a century, although there is wide regional variation. In the UK, it remains one of the most commonly used forms of analgesia in labour despite little objective evidence of its efficacy. Most of its side effects are theoretical and transient and this has contributed to its popularity. N2O forms part of the routine general anaesthetic technique for Caesarean section and gynaecological surgery although there are theoretical risks in its usage for the latter. Despite the decline in use of N2O for anaesthesia generally, there appears to be no obvious replacement for N2O analgesia for labour.