Irish Journal of Medical Science (1971 -)

, Volume 185, Issue 2, pp 371–381 | Cite as

Metformin versus insulin in gestational diabetes mellitus: a meta-analysis of randomized clinical trials

  • B. Zhu
  • L. Zhang
  • Y. Y. Fan
  • L. Wang
  • X. G. Li
  • T. Liu
  • Y. S. Cao
  • Z. G. Zhao
Original Article



Metformin is widely used in treatment of type 2 diabetes. However, whether it is safe for use in pregnancy is controversial.


A search for relevant studies were performed using PubMed (1948–2014), Embase (1974–2014), the Web of knowledge (1950–2014), and the Cochrane database, included all randomized control trials published in English.


Eight RCTs (1712 patients with gestational diabetes mellitus) were retrieved; of those 853 patients were given metformin, and 859 patients were given insulin. Our results showed that metformin does not increase risk of prematurity (RR = 1.26; 95 % CI [0.89, 1.79], P = 0.19). In addition, metformin can either decrease the total weight gain [MD = −1.49, 95 % CI (−2.66, −0.31), P = 0.01] or weight gain after randomization [MD = −1.23, 95 % CI (−1.75, −0.71), P < 0.00001]. No significant differences were observed in patients with pre-eclampsia [RR = 0.82, 95 % CI (0.56, 1.2), P = 0.32] or caesarean section [RR = 0.93, 95 % CI (0.75, 1.16), P = 0.53]. Use of metformin also significantly decreased the risk of neonatal hypoglycemia [RR = 0.58, 95 % CI (0.43, 0.78), P = 0.0003] and admission rates to neonatal intensive care units [RR = 0.74, 95 % CI (0.61, 0.89), P = 0.002]. No other adverse effects were observed, such as hyperbilirubinaemia [RR = 0.83, 95 % CI (0.64, 1.08), P = 0.16], large for gestational age [RR = 0.85, 95 % CI (0.68, 1.05), P = 0.14], small for gestational age [RR = 0.92, 95 % CI (0.61, 1.39), P = 0.69], macrosomia [RR = 0.75, 95 % CI (0.54, 1.03), P = 0.07] or respiratory distress syndrome [RR = 0.88, 95 % CI (0.55, 1.41), P = 0.6].


Metformin may be beneficial in treating gestational diabetes. However, even more studies are needed to provide more evidence for the future use of metformin.


Gestational diabetes mellitus Metformin Insulin Randomized control trials 


Compliance with ethical standards

Conflict of interest

The authors declare no competing financial interests.


This study was funded by National Natural Scientific Foundation of China [Grant number: 81402814].


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Copyright information

© Royal Academy of Medicine in Ireland 2016

Authors and Affiliations

  • B. Zhu
    • 1
  • L. Zhang
    • 2
  • Y. Y. Fan
    • 3
  • L. Wang
    • 4
  • X. G. Li
    • 1
  • T. Liu
    • 1
  • Y. S. Cao
    • 5
  • Z. G. Zhao
    • 1
  1. 1.Beijing Tian Tan HospitalCapital Medical UniversityBeijingChina
  2. 2.Beijing Shijitan HospitalCapital Medical UniversityBeijingChina
  3. 3.Beijing Tongren HospitalCapital Medical UniversityBeijingChina
  4. 4.The Third Affiliated Hospital of Beijing University of Chinese MedicineBeijingChina
  5. 5.Dong Fang Hospital-The Second Affiliated Hospital of Beijing University of Chinese MedicineBeijingChina

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