Metformin found to be safe during pregnancy

The study found no major adverse events of metformin during pregnancy. This is good news as metformin is an important intervention for hyperglycemia of pregnancy. The following birth outcomes were assessed: cesarean section, neonatal weight, and serious neonatal adverse events.


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Metformin in Pregnancy



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Journal of Diabetes


January 2019


In Australia’s Northern Territory, Indigenous mothers account for 33% of births and have high rates of hyperglycemia in pregnancy. The prevalence of type 2 diabetes (T2D) in pregnancy is up to 10‐fold higher in Indigenous than non‐Indigenous Australian mothers, and the use of metformin is common.

  • We assessed birth outcomes in relation to metformin use during pregnancy from a clinical register.


The study included women with gestational diabetes (GDM), newly diagnosed diabetes in pregnancy (DIP), or pre‐existing T2D from 2012 – 2016.

Data were analyzed for metformin use in the third trimester.

Regression models were adjusted for maternal age, body mass index, parity, and insulin use.


Of 1649 pregnancies, 814 (49.4%) were to Indigenous women, of whom 234 (28.7%) had T2D (vs 4.6% non‐Indigenous women; P < 0.001). Metformin use was high in Indigenous women (84%‐90% T2D, 42%‐48% GDM/DIP) and increased over time in non‐Indigenous women (43%‐100% T2D, 14%‐35% GDM/DIP).

Among Indigenous women with GDM/DIP, there were no significant differences between groups with and without metformin in cesarean section (51% vs 39%; adjusted odds ratio [aOR] 1.25, 95% confidence interval [CI] 0.87‐1.81), large for gestational age (24% vs 13%; aOR 1.5, 95% CI 0.9‐2.5), or serious neonatal adverse events (9.4% vs 5.9%; aOR 1.32, 95% CI 0.68‐2.57).

Metformin use was independently associated with earlier gestational age (37.7 vs 38.5 weeks), but the risk did not remain independently higher after exclusion of women managed with medical nutrition therapy alone, and the increase in births <37 weeks was not significant on multivariate analysis.


We found no clear evidence of any adverse outcomes related to the use of metformin for the treatment of hyperglycemia in pregnancy.

Pregnancy Metformin