The purpose of this study is to determine the effect of maternal hydration with oral isotonic solution and water on amniotic fluid (AF) index in women with normohydramnios.

Objective: To determine the effect of maternal hydration with oral isotonic solution and water on amniotic fluid (AF) index in women with normohydramnios.

Subjects and Methods: Women with normal AF index and gestational age between the 33 and 36 weeks without maternal complications were randomized into three groups (isotonic solution, water, control). The isotonic solution and water groups were instructed to drink 1.5L of respective solution; the control group was instructed to drink 200mL of water. AF index was measured before and after hydration. The investigator performing the AF index was blinded to the subject's group.

Results: Ninety-nine women completed the study without any maternal adverse effects. The mean increase in amniotic fluid index after hydration was significantly greater in the isotonic solution and water groups (12.1mm, p=0.02; 13.1mm, p=0.05; respectively) than the control group (1.4mm, p=0.74). There was no significant difference between the isotonic solution and water groups. Hydration with isotonic solution and water improved the chance of 20% of increase of amniotic fluid index in 10.2 (95% CI 1.9-98.9) and 6.0 (95% CI 1.0-45.5) times respectively.

Conclusion: Maternal hydration with isotonic solution or water increased AF index in women with normohydramnios.

Inclusion Criteria:

• gestational age between 33 and 36 weeks
• singleton pregnancy
• intact membranes
• initial AF index between 5 and 95 per cent

Exclusion Criteria:

• no maternal complications
• no fetal structural malformation
• no evidence of fetal distress on nonstress test