Effect of maternal hydration on oligohydramnios: a comparison of three volume expansion methods. Maternal hydration increases amniotic fluid index. Maternal hydration increases amniotic fluid index in women with normal amniotic fluid. A randomized clinical trial comparing the effect of maternal intravenous hydration and placebo on the amniotic fluid index in oligohydramnios.
To determine the effect of maternal hydration with intravenous (i.v.) isotonic fluid, i.v. hypotonic fluid, and oral water on amniotic fluid index (AFI) in women with oligohydramnios.
                Patients with low AFI and gestational age over 35 weeks without maternal complications were randomized into four groups (2 L/2 h i.v. isotonic fluid, 2 L/2 h i.v. hypotonic fluid, 2 L/2 h oral water, control). Maternal plasma osmolality, AFI, hematocrit, and hemoglobin concentration were measured before and after hydration.
                Eighty-four patients (n=21/group) completed the study without any maternal adverse effects. The mean increase in AFI after hydration was significantly greater in the i.v. hypotonic and oral water groups (2.8+/-1.9, P < .001; 3.8 +/-1.9, P < .001, respectively), but not in the i.v. isotonic group (0.5+/-1.1), compared with the control group (0.5+/-1.1). Significant decreases in maternal hematocrit and hemoglobin concentration were found only after i.v. isotonic hydration (32.0+/-2.9 to 29.5+/-2.3, P < .001; 11.0+/-1.6 to 10.1+/-1.4, P < .001, respectively). Changes in maternal osmolality correlated with the changes in AFI in both the i.v. hypotonic group (r=.58, P < .001) and oral water group (r =.63, P < .001).
                Maternal hydration with either i.v. hypotonic fluid or oral water increases AFI in oligohydramnios. Maternal osmotic change rather than maternal volume expansion had a more direct impact on increasing amniotic fluid volume with short-term acute hydration. Although adequate amniotic fluid (AF) volume is considered an important aspect of fetal well-being, the etiology of decreased AF volume is not well understood. A randomized blinded trial was designed to examine our hypothesis that maternal hydration would increase the AF index in women with low AF indexes. Women seen in our testing centers were randomized into control or hydration groups. The control group was instructed to drink their normal amount of fluid; the hydration group was instructed to drink 2 L of water, in addition to their usual amount of fluid, 2-4 hours before the post-treatment AF index. The women returned for the post-treatment AF index the same or following day. The mean post-treatment AF index was significantly greater in the hydration group (6.3 versus 5.1; P less than .01), as was the mean change in AF index (post-treatment AF index--pre-treatment AF index: 1.5 versus 0.31; P less than .01). These findings suggest that maternal oral hydration increases AF volume in women with decreased fluid levels. To test the hypothesis that maternal oral hydration would increase the amniotic fluid (AF) index in pregnancies with normal AF.
                Forty women with a normal AF index (7.0-24.0 cm) were randomized to either the control or hydration group. Women in the hydration group drank 2 L of water and returned for the post-treatment AF index in 4-6 hours, whereas women in the control group drank only 100 mL of water during the same time period. The investigator performing the AF index was blinded to the subject's group. The pre- and post-treatment AF indexes and maternal urine specific gravities were compared between the groups.
                The mean AF index in the hydration group increased significantly by 3.0 +/- 2.4 cm (P < or = .0001) whereas it declined significantly by 1.5 +/- 2.7 cm in the control group (P < or = .02). The maternal urine specific gravities also changed significantly in the expected direction, with those in the hydration group decreasing and those in the control group increasing (P < or = .0001). There was a regression coefficient of -0.6 (P < or = .0001) between the change in urine specific gravity and the change in AF index. The mean time between the pre- and post-treatment AF indexes was not different between the groups.
                Maternal oral hydration increased the AF index by approximately 16%, whereas fluid restriction decreased the AF index by 8% in women with normal AF. These findings support previous data that maternal hydration increased the AF index by 31% in women with decreased AF and suggest that maternal fluid volume or osmolality may have a role in maintaining the AF volume. To compare the treatment of acute intravenous hydration with placebo in term pregnant women manifesting oligohydramnios.
                All patients with oligohydramnios who met the inclusion criteria were offered participation in this randomized, double-blind, placebo-controlled study. After ruling out rupture of membranes and maternal and fetal complications, we recruited 44 women with third trimester singleton pregnancies having an amniotic fluid index (AFI) of less than 6. Patients were randomized into treatment or control groups. Patients in the treatment group received a continuous intravenous infusion of (1/2) normal saline (NS) at a rate of 1000 mL/h for two hours. Patients in the placebo group received an intravenous infusion of (1/2) NS at 10 mL/h for two hours. The AFI was re-assessed by the same sonographer one hour after the hydration was completed. Both the patient and the examiner were blinded to the study groups.
                Maternal age, parity, gestational age, and birth weight were not significantly different between the two groups. The AFI increased significantly in both treatment (3.8 +/- 1.2 vs. 5.3 +/- 2.5, p < 0.05) and placebo (4 +/- 1.3 vs. 5.5 +/- 2.4, p < 0.05) groups. Moreover, the changes in AFI did not significantly differ between the treatment and the placebo groups (1.2 +/- 2.1 vs. 1.5 +/- 2.1, respectively; p > 0.05).
                There are statistically significant short-term increases in the AFI in patients with oligohydramnios whether the patients are treated with intravenous fluids or not. The short-term increase in AFI may reflect physiologic diurnal variations in the amniotic fluid.
Simple maternal hydration appears to increase amniotic fluid volume and may be beneficial in the management of oligohydramnios and prevention of oligohydramnios during labour or prior to external cephalic version. Controlled trials are needed to assess the clinical benefits and possible risks of maternal hydration for specific clinical purposes.