Amniotic fluid is important for the maintenance of good fetal well-being. The current recommended management for isolated oligohydramnios without maternal and fetal complications is maternal hydration through intravenous or oral solution to increase the amniotic fluid volume. This study was conducted to determine the efficacy of oral isotonic versus oral hypotonic solution for maternal hydration in the management of borderline oligohydramnios. This is a prospective open label randomizedcontrolled trial with 123 participants, 18 to 38 years old, singleton pregnancies, 32 to 35 weeks age of gestation, with borderline oligohydramnios without maternal and fetal complications seen in a tertiary medical center. There were 62 participants who took 2 liters of isotonic solution and 1 liter of hypotonic solution, while 61 participants drank 3 liters of hypotonic solution. Repeat AFI was done by ultrasonography after 24 and 48 hours post-hydration therapy. Results revealed no significant difference with regards to comparison of the amount of fluids taken between the two treatment arms. However, when the AFI was measured 24 and 48 hours posthydration therapy, the isotonic solution showed a significantly higher AFI. Furthermore, the participants on the isotonic solution group showed a significantly higher mean difference in the AFI from the baseline for both 24 and 48 hours post-hydration. Maternal oral hydration therapy using isotonic solution is an efficacious treatment among pregnant women with borderline oligohydramnios. It is readily available and offers low cost management since it does not require hospitalization. With compliance to oral hydration therapy, improved perinatal outcomes can be expected.