Objectives: Gestational diabetes mellitus (GDM) is a common disorder in pregnant women. Long noncoding RNA (lncRNA) is a fundamental mediator in the pathogenesis of GDM. The study aimed to detect the clinical importance of lncRNA OIP5-AS1 and its underlying regulation on trophoblast cells. Design: The expression of OIP5-AS1 and miR-137-3p was assessed by the quantitative real-time PCR technique. The prognostic effect of OIP5-AS1 was analyzed by the receiver operating characteristic curve. The influences of OIP5-AS1 on cells were indicated by cell counting kit-8, transwell experiments, and flow cytometry. Luciferase activity assay was used to identify the target relationships among OIP5-AS1, miR-137-3p, and EZH2. Participants: A total of 75 pregnant women with GDM who were treated in the Dongying People’s Hospital were selected as the GDM group. Besides, 72 pregnant women with non-GDM who underwent physical examination in the same hospital were selected as the control group. Results: Decreased expression of OIP5-AS1 was confirmed in GDM patients, and the level of OIP5-AS1 could be used as a basis for evaluating GDM patients. Upregulation of OIP5-AS1 ameliorated the viability, migration, invasion, and apoptosis of HG-stimulated HTR-8/SVneo cells by sponging miR-137-3p. EZH2 was a direct target of miR-137-3p. Conclusions: OIP5-AS1 level decreased in women with GDM. OIP5-AS1 appeared to help separating GDM patients from healthy pregnant women. The OIP5-AS1/miR-137-3p/EZH2 pathway could exert its function on HG-induced HTR-8/SVneo models.