Comparative effectiveness of initiating insulin versus metformin therapy for gestational diabetes mellitus in China: a retrospective cohort study
4 affiliations
- 1Department of Pharmaceutical Regulatory Science and Pharmacoeconomics, School of Pharmacy, Nanjing Medical University, Nanjing, Jiangsu 211166 China
- 2School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, China
- 3Institute for Global Health and Development, Peking University, Beijing, 100871 China
- 4Department of Pharmacy, The Second People’s Hospital of Changzhou, The Third Affiliated Hospital of Nanjing Medical University, Changzhou, Jiangsu 213004 China
Abstract
Background: While insulin is widely recommended as the first-line pharmacological therapy for gestational diabetes mellitus (GDM), the use of metformin is increasing in routine clinical practice. However, real-world evidence comparing their effectiveness and safety remains limited. This study aimed to evaluate glycemic control and adverse pregnancy outcomes between the insulin and the metformin initiation group in women with GDM in China.
Methods: We conducted a retrospective cohort study using electronic medical records from a provincial healthcare database in Eastern China. Women diagnosed with GDM between 2018 and 2025 were included. Patients were divided into the insulin initiation group and the metformin initiation group based on their first prescription. Propensity score overlap weighting (OW) was used to balance baseline characteristics. Weighted linear and logistic regression models were used to assess glycemic outcomes, including the glycated hemoglobin (HbA1c) level at the end of pregnancy, the change in HbA1c, and target achievement (HbA1c < 6.0%). Adverse pregnancy outcomes were evaluated using weighted Cox proportional hazards models with gestational age as the time scale.
Results: Of the 7,397 women included, 6,922 (93.6%) initiated insulin and 475 (6.4%) initiated metformin therapy. After OW adjustment, no significant differences were found between the two groups in end-of-pregnancy HbA1c levels, HbA1c changes, or glycemic control rates. Compared with insulin initiation, metformin initiation was associated with significantly lower risks of cesarean delivery (HR: 0.77, 95% CI: 0.62–0.95; P = 0.017), premature rupture of membranes (HR: 0.66, 95% CI: 0.48–0.93; P = 0.016), and macrosomia (HR: 0.61, 95% CI: 0.40–0.93; P = 0.021). Risks for other adverse outcomes, including preterm birth and preeclampsia, were comparable. Sensitivity analyses, including per-protocol analysis, confirmed the robustness of these findings.
Conclusions: In this real-world Chinese cohort, the metformin initiation group achieved glycemic control similar to the insulin initiation group. In addition, the metformin initiation group had lower risks of cesarean delivery, premature rupture of membranes, and macrosomia. These findings suggest that metformin may be a viable and effective initial treatment option for selected women with GDM.
Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s12884-026-09752-4.
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BibTeX
@article{jiang2026comparative,
title = {{Comparative effectiveness of initiating insulin versus metformin therapy for gestational diabetes mellitus in China: a retrospective cohort study}},
author = {Linfeng Jiang and Nan Peng and Mengyao Xue and Ruolan Wei and Guoxian Lu and Yuqing Fan and Shuo Zhang and Beini Lyu and Dongning Yao},
journal = {BMC Pregnancy and Childbirth},
year = {2026},
month = jul,
doi = {10.1186/s12884-026-09752-4},
url = {https://doi.org/10.1186/s12884-026-09752-4},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Comparative effectiveness of initiating insulin versus metformin therapy for gestational diabetes mellitus in China: a retrospective cohort study
AU - Linfeng Jiang
AU - Nan Peng
AU - Mengyao Xue
AU - Ruolan Wei
AU - Guoxian Lu
AU - Yuqing Fan
AU - Shuo Zhang
AU - Beini Lyu
AU - Dongning Yao
PY - 2026
DA - 2026/07/31
JO - BMC Pregnancy and Childbirth
DO - 10.1186/s12884-026-09752-4
UR - https://doi.org/10.1186/s12884-026-09752-4
AB - Background: While insulin is widely recommended as the first-line pharmacological therapy for gestational diabetes mellitus (GDM), the use of metformin is increasing in routine clinical practice. However, real-world evidence comparing their effectiveness and safety remains limited. This study aimed to evaluate glycemic control and adverse pregnancy outcomes between the insulin and the metformin initiation group in women with GDM in China. Methods: We conducted a retrospective cohort study using electronic medical records from a provincial healthcare database in Eastern China. Women diagnosed with GDM between 2018 and 2025 were included. Patients were divided into the insulin initiation group and the metformin initiation group based on their first prescription. Propensity score overlap weighting (OW) was used to balance baseline characteristics. Weighted linear and logistic regression models were used to assess glycemic outcomes, including the glycated hemoglobin (HbA1c) level at the end of pregnancy, the change in HbA1c, and target achievement (HbA1c < 6.0%). Adverse pregnancy outcomes were evaluated using weighted Cox proportional hazards models with gestational age as the time scale. Results: Of the 7,397 women included, 6,922 (93.6%) initiated insulin and 475 (6.4%) initiated metformin therapy. After OW adjustment, no significant differences were found between the two groups in end-of-pregnancy HbA1c levels, HbA1c changes, or glycemic control rates. Compared with insulin initiation, metformin initiation was associated with significantly lower risks of cesarean delivery (HR: 0.77, 95% CI: 0.62–0.95; P = 0.017), premature rupture of membranes (HR: 0.66, 95% CI: 0.48–0.93; P = 0.016), and macrosomia (HR: 0.61, 95% CI: 0.40–0.93; P = 0.021). Risks for other adverse outcomes, including preterm birth and preeclampsia, were comparable. Sensitivity analyses, including per-protocol analysis, confirmed the robustness of these findings. Conclusions: In this real-world Chinese cohort, the metformin initiation group achieved glycemic control similar to the insulin initiation group. In addition, the metformin initiation group had lower risks of cesarean delivery, premature rupture of membranes, and macrosomia. These findings suggest that metformin may be a viable and effective initial treatment option for selected women with GDM. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s12884-026-09752-4.
SN - 1471-2393
ER -