Background: Hydration has been proposed as a treatment for women with preterm labour. Theoretically, hydration may reduce uterine contractility by increasing uterine blood flow and by decreasing pituitary secretion of antidiuretic hormone and oxytocin.
Objectives: To evaluate the effectiveness of intravenous or oral hydration to avoid preterm birth and its consequences in women with preterm labour.
Search strategy: The Cochrane Pregnancy and Childbirth Group trials register (January 2002), the Cochrane Controlled Trials register (The Cochrane Library, Issue 1, 2002) and bibliographies of relevant papers were searched.
Selection criteria: Randomised controlled trials, including women with a viable pregnancy less than 37 completed weeks' gestation and presenting with preterm labour, comparing intravenous or oral hydration with no treatment. The intervention might or might not be associated with bed rest. Studies comparing tocolytic drugs with intravenous fluids used in the control group as a placebo were not included in this review.
Data collection and analysis: Two reviewers independently assessed the reports, to determine if the study met the inclusion criteria and to evaluate the methodological quality. Data were extracted independently by two of the reviewers. The results were expressed as relative risks (RR) for dichotomous outcomes and weighted mean difference for continuous outcomes.
Main results: Two studies, including a total of 228 women with preterm labour and intact membranes, compared intravenous hydration with bed rest alone. Risk of preterm delivery, before 37 weeks (relative risk (RR): 1.09; 95% confidence interval (CI): 0.71-1.68), before 34 weeks (RR: 0.72; 95% CI: 0.20-2.56) or before 32 weeks (RR: 0.76; 95% CI: 0.29-1.97), was similar between groups. Admission to neonatal intensive care unit occurred with similar frequency in both groups (RR: 0.99; 95% CI: 0.46-2.16). Cost of treatment was slightly higher (US$39) in the hydration group. This difference was not statistically significant and only includes hospital costs during a visit of less than 24 hours. No studies evaluated oral hydration.
Reviewer's conclusions: The data are too few to support the use of hydration as a specific treatment for women presenting with preterm labour. The two small studies available do not show any advantage of hydration compared to bed rest alone. Intravenous hydration does not seem to be beneficial, even during the period of evaluation soon after admission, in women with preterm labour. Women with evidence of dehydration may, however, benefit from the intervention.