This study was designed to observe the effects of i.v. fluid infusion
on uterine activity during normal labour in women receiving an extradu
ral block. Thirty-four women in spontaneous labour at term gestation w
ere allocated randomly and prospectively to one of three i.v. pre-extr
adural fluid load groups: group A, no fluid load; group B, normal sali
ne 500 ml; and group C, normal saline 1000 ml. Continuous internal mea
surement of uterine activity was observed before, during and after flu
id infusion and extradural block. In groups A and B, uterine activity
did not change. In group C, uterine activity decreased after infusion
of saline (P < 0.01) and returned to baseline over the next 20 min. Ex
tradural block was not associated with a change in uterine activity. H
ypotension was not increased in the group that received no fluid prelo
ad.