Objective: To investigate the value of glycosylated hemoglobin (HbAlc) in monitoring blood glucose and predicting maternal and neonatal outcomes, via evaluating the relationship between HbAlc level in pregnant women with gestational diabetes mellitus (GDM) before delivery and adverse maternal and neonatal outcomes. Methods: We retrospectively analyzed the clinical data of 593 pregnant women with GDM who delivered in Maternal and Child Health Hospital Affiliated to Anhui Medical University from January to June 2019. According to the level of HbAlc before delivery, patients were divided into 3 groups: A total of 229 pregnant women with HbAlc <5.5% in group A, 284 pregnant women with 5.5%≤ HbAlc ≤6.0% in group B, and 80 pregnant women with HbAlc >6.0% in group C. Differences of the maternal and neonatal outcomes among these three groups were compared and analyzed. High risk factors of adverse maternal and neonatal outcomes were analyzed by binary logistic regression. The receiver operating characteristic (ROC) curve was used to evaluate the value of HbAlc levels as an indicator in adverse maternal and infant outcomes. Results: 1) The incidence of hypertensive disorder complicating pregnancy (HDCP), macrosomia, and neonatal body mass index (BMI) in group C were significantly higher than those in group A and group B (all P<0.05), and there was no significant difference between group A and group B (P>0.05). The incidence of polyhydramnios, premature rupture of fetal membranes, and fetal distress was the highest in group C, which was statistically significant compared with group A (P<0.05), but there was no statistical significance compared with group B (P>0.05). Group C presented the highest incidence of preterm birth, which was statistically significant compared with group B (P<0.05), but was not significantly different from that of group A (P>0.05). There were no statistically significant differences in the incidence of cesarean section, postpartum hemorrhage, neonatal asphyxia, and fetal death among these 3 groups (all P>0.05). Results from Pearson product-moment correlation analysis also showed that neonatal BMI was positively correlated with HbAlc level (r=0.167, P<0.05). 2) The result of binary logistic regression analysis indicated that the increase of HbAlc level was the risk factor of adverse maternal and neonatal outcome (OR in group B: 1.477, 95% CI: 1.011 to 2.158, P<0.05. OR in group C: 1.848, 95% CI: 1.022 to 3.344, P<0.05). HbAlc can be used as an indicator for predicting adverse maternal and neonatal outcome. The area under curve (AUC) was 0.601(P<0.001). Conclusion: HbAlc level before delivery can be used as an auxiliary indicator for monitoring blood glucose during pregnancy and predicting adverse maternal and neonatal outcomes in GDM pregnant women.