Effect sizes were similar across all diabetes in pregnancy groups: insulin (12 studies26–28,30,31,41–47 n = 3048) (Fig. 2c), glyburide (2 studies33,48 n = 253) (Fig. 2d) and placebo (OR 1.29, 95% CI 0.77–2.16, I2 = N/A, p = 0.34) (1 study36 n = 482). Here, INS is linked to diabetes mellitus.