INS and diabetes mellitus: Effect sizes were similar and non-significant in all diabetes in pregnancy sub-groups: FBS: insulin (14 studies26–28,31,32,41–46,50,51,56 n = 2945), glyburide (4 studies33–35,48, n = 525) (Supplementary Fig. S9b and c), and placebo (1 study36, n = 140) (OR − 2.40, 95% CI − 6.98 to 2.18; I2 = N/A, p = 0.30).