To analyze the effects of dietary intervention combined with insulin aspart on the serum levels of nesfatin-1, C1q/TNF related protein-12 (CTRP12), and pregnancy outcomes in pregnant women with gestational diabetes mellitus (GDM). In this retrospective cohort study, 513 women with GDM admitted to Tangshan Central Hospital (Tangshan, China) between January 2019 and December 2022 were selected and divided into an observation group (dietary intervention combined with insulin aspart therapy; n = 284) and a control group (insulin aspart therapy, n = 229). The general characteristics, clinical outcomes, serum nesfatin-1 and CTRP12 levels, 2-hour postprandial blood glucose levels, pregnancy outcomes, and perinatal outcomes of the 2 groups were compared. After treatment, the total effective rate in the observation group was significantly higher than that of the control group (97.54% vs 86.03%, respectively; P < .001). Compared with the pretreatment levels, nesfatin-1 and CTRP12 levels were decreased in both groups; nesfatin-1 and CTRP12 levels in the observation group were significantly higher than those in the control group. After treatment, the preprandial and 2-hour postprandial blood glucose levels in the observation group were significantly lower than those in the control group. Compared with the control group, the observation group had significantly fewer cesarean sections, and a significantly lower incidence of postpartum hemorrhage, premature rupture of membranes, and other adverse pregnancy outcomes. After treatment, the risks of preterm birth, macrosomia, fetal distress, neonatal asphyxia, neonatal hypoglycemia, and other adverse perinatal outcomes were significantly lower in the observation group than in the control group. In pregnant women with GDM, dietary intervention combined with insulin aspart can improve clinical outcomes; reduce nesfatin-1, CTRP12, and blood glucose levels; and reduce the incidence of adverse pregnancy outcomes.