OBJECTIVE: The purpose of this study was to determine the effect of short-term (48 hour) indomethacin therapy on amniotic fluid volume. STUDY DESIGN: Patients who were admitted to Northwestern Memorial Hospital in preterm labor and who received indomethacin tocolysis were eligible for the study. Thirty-five patients with singleton gestations and 26 patients with twin gestations were enrolled. Amniotic fluid volumes were measured at baseline, at 48 hours after the initiation of indomethacin, and then every 24 hours thereafter for a maximum of 7 days. RESULTS: There were no significant changes in mean amniotic fluid volume subsequent to the administration of indomethacin at any of the time points that were measured. Among the 61 patients who received indomethacin, there were 2 cases of oligohydramnios (3.3%; 95% CI, 0.03%, 11.3%). In both cases, the amniotic fluid index returned to normal within 24 hours after the discontinuation of indomethacin. CONCLUSION: Short-term indomethacin therapy, in either singleton or twin gestations, does not cause a clinically significant change in amniotic fluid volume.