Abstract: Objective To investigate the status of vitamin B12 deficiency in patients with third‐trimester diabetes and explore its influencing factors. Methods Patients with third‐trimester diabetes who underwent prenatal examination at a hospital in Wuxi from June 2018 to June 2022 were selected as the study subjects. Vitamin B12 deficiency was investigated at 28 weeks of gestation. Descriptive analysis method was used to analyze the results, and univariate and multivariate analysis methods was used to analyze the influencing factors of vitamin B12 deficiency in patients with third‐trimester diabetes. Results A total of 1 355 patients with third‐trimester diabetes participated in the survey, and 1 235 valid data were included, with an effective rate of 91.14%. Vitamin B12 deficiency occurred in 260 of 1 235 patients （21.05%）. Multivariate logistic regression analysis showed that metformin treatment （OR=3.862）, vegetarian experience for more than one year （OR=2.002）, inadequate livestock meat intake （OR=2.357）, hypothyroidism （OR=1.549）, Helicobacter pylori infection （OR=1.551）, and occasional or no multivitamin supplementation （OR=8.575, 2.276） were the influencing factors of Vitamin B12 deficiency in patients with third‐trimester diabetes. Conclusions The prevalence of vitamin B12 deficiency is elevated among patients with third‐trimester diabetes. Factors such as metformin treatment, vegetarian experience for more than one year, inadequate livestock meat intake, hypothyroidism, Helicobacter pylori infection, and prenatal insufficiency multivitamin supplementation all contribute to the development of vitamin B12 deficiency. It is recommended that clinical interventions be tailored based on these factors to assist patients in elevating their vitamin B12 levels and enhancing pregnancy outcomes.

Key words: Gestational diabetes, Third‐trimester, Vitamin B12 deficiency, Influencing factor