Objectives:

To clarify the role of metformin in the prevention of gestational diabetes in obese non-diabetic pregnant women.

Data sources:

The Cochrane Library, Canadian Medical Association Infobase, Database of Abstracts of Reviews of Effects, NICE Guidelines Finder, National Guideline Clearinghouse, BMJ Clinical Evidence, PubMed, and Portuguese Medical Journals Index.

Review methods:

In June 2020, we searched for meta-analysis, systematic reviews, controlled and randomized clinical trials and clinical guidelines published between May 2010 and May 2020, in Portuguese and English. The searched MeSH terms were: Pregnancy, Obesity, Metformin, Diabetes Gestational and the terms Health Sciences Descriptors ‘Gravidez’, ‘Obesidade’, ‘Metformina’, ‘Diabetes gestacional’. We used the American Family Physician's Strength Of Recommendation Taxonomy (SORT) scale to classify the evidence.

Results:

The search provided 152 articles, of which three met the inclusion criteria and were selected. A 2018 Cochrane review, based on three randomized and randomized controlled trials (ECAC) with a total of 1,099 pregnant women, found no differences in the rate of gestational diabetes in the metformin vs. placebo groups (level of evidence 1). A meta-analysis by Chatzakis et al. evaluated four ECAC, including 624 women, and concluded that metformin does not diminish the risk of developing gestational diabetes (level of evidence 1). Sales et al. included 164 pregnant women (82 metformin vs 82 control) and concluded that the use of metformin is not effective in preventing gestational diabetes (level of evidence 2).

Conclusions:

There is no available evidence to recommend metformin use for GD prevention in obese pregnant women (strength of recommendation A).

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