Abstract： Objective:To investigate the effects of birth intervals on maternal and infant outcomes in pregnant women with gestational diabetes mellitus (GDM).Methods:This retrospective study recruited 445 pregnant women with GDM who received prenatal examinations and delivered in Peking University First Hospital-Ningxia Women Children's Hospital from January 2020 to December 2021. Based on the birth interval classification standard recommended by WHO and the American College of Obstetricians and Gynecologists, these subjects were divided into three groups: shorter group (<18 months, n=69), normal group (18-59 months, n=213) and longer group (≥60 months, n=163). Analysis of variance, Chi-square test, and multivariate logistic regression model were used for statistical analysis. Results:There were statistically significant differences in the maternal age at this and previous pregnancy [(30.6±4.1), (30.8±3.8) vs (32.7±3.7) years; (22.7±2.4), (26.3±2.9) vs (29.9±4.1) years] and the incidence of oligohydramnios [10.1% (7/69), 1.9% (4/213) vs 3.1% (5/163)] and preterm birth [14.5% (10/69), 5.2% (11/213) vs 1.8% (3/163)] between the shorter, normal, and longer groups (all P<0.05). After adjusting for confounding factors in the present pregnancy, the risks of oligohydramnios, preterm birth, and low birth weight increased in the shorter group [ OR (95% CI): 4.73 (1.75-12.85), 5.54 (1.37-22.42) and 9.54 (3.05-29.82), all P<0.05] and so did the risk of postpartum hemorrhage in the longer group [ OR (95% CI): 4.45 (1.72-11.49), P<0.05]. Conclusions:Both longer and shorter birth intervals can affect maternal and infant outcomes of GDM patients. Postpartum healthcare should be strengthened for GDM patients who desire more children to help them maintain an appropriate birth interval, thus promoting maternal and infant health.