INS and diabetes mellitus: Effect sizes were similar across all diabetes in pregnancy groups: − 1.57 kg for insulin (p = 0.0004) (7 studies26–32 n = 935) (Fig. 1b), − 1.67 kg for glyburide (p = 0.02) (3 studies33–35 n = 376) (Fig. 1c) and − 1.50 kg for placebo (95% CI − 2.39 to − 0.61, I2 = N/A, p = 0.001) (1 study36 n = 482).