Third, in most trials directly comparing metformin with insulin, women receiving metformin were also given supplemental insulin ‘if required’; in one of the largest trials, this equated to 46% of the metformin group.59 Therefore, our results more appropriately relate to metformin’s greater effectiveness as a first-line treatment for GDM rather than a standalone treatment compared with insulin. The gene discussed is INS; the disease is gestational diabetes.