Group differences are compared with chi-square test. When significant differences are found or when cases are few, Fischer's exact test is performed to analyse differences between fluid groups 1 and 3.
*  Vaginal <4 hours or <4 hours: Vaginal delivery, labour of shorter or longer duration than 4 hours. Epidural: epidural or spinal analgesia.
**  Induction versus spontaneous onset of labour.
***  Vaginal spontaneous delivery versus instrumental vaginal delivery plus delivery by emergency caesarean section.
****  One woman received combined spinal-epidural analgesia during labour.
*****  Calculation only includes women who received oxytocin for augmentation of labour.