Background: Fetal heart rate changes are common following regional analgesia (epidural or spinal) during labour. Reduced uterine blood flow from maternal hypotension (low blood pressure) may contribute to this. Intravenous fluid preloading (volume expansion) may help to reduce maternal hypotension. Newer protocols using weaker solutions of local anaesthetic, and opioid only blocks, may reduce the need for preloading.
Objectives: The objective of this review was to assess the effects of prophylactic intravenous fluid preloading prior to epidural analgesia during labour on maternal and fetal well-being.
Search strategy: The Cochrane Pregnancy and Childbirth Group trials register (November 2001) and the Cochrane Controlled Trials Register (The Cochrane Library, Issue 3, 2001) were searched.
Selection criteria: Randomised and quasi-randomised trials comparing prophylactic intravenous preloading before epidural analgesia during labour with a control group (dummy or no preloading).
Data collection and analysis: The reviewer assessed trial quality and extracted data.
Main results: For high dose local anaesthetic blocks, one study involving 102 women was included. There was potential for considerable bias in this trial. Preloading with intravenous fluids was associated with a reduction in hypotension (relative risk 0.07, 95% confidence interval 0.01 to 0.53). It was also associated with a reduction in fetal heart rate abnormalities (relative risk 0.36, 95% confidence interval 0.16 to 0.83). No differences were detected in other perinatal and maternal outcomes. The trials in women receiving low-dose local anaesthetic (95 women) or opioid only blocks (30 women) demonstrated no statistically significant differences in maternal hypotension or fetal heart rate abnormality, but were too small to exclude the possibility of moderate effects with certainty.
Reviewer's conclusions: There are methodological limitations in the trials studied. However, preloading prior to high-dose local anaesthetic blocks may have beneficial fetal and maternal effects in healthy women. Further investigation of the effects in women receiving low-dose local anaesthetic or opioid only blocks, and the risks and benefits of intravenous preloading for women with pregnancy complications, is required.