Tarry-Adkins JL, et al. - A systematic review of 28 studies that involved 3,976 mothers who were randomized to metformin or insulin for the treatment of gestational diabetes mellitus (GDM) was done and all studies that reported the weight and growth of their babies in the womb, at birth, or later in childhood were included. Newborns whose mothers were treated with metformin weighed on average 108 g less at birth in comparison with those whose mothers were treated with insulin and had a lower risk of being born big (> 90th centile) for their gestation at delivery. By 18–24 months, metformin-exposed infants were 0.44 kg heavier than insulin-exposed infants. By mid-childhood (5–9 years), greater BMI (by 0.8 kg/m²) was noted in metformin-exposed children than insulin-exposed children. Thus, neonates are significantly smaller compared with neonates whose mothers were treated with insulin during pregnancy, after intrauterine exposure to metformin for treatment of maternal GDM. Irrespective of the lower average birth weight, metformin-exposed children seem to experience quickened postnatal growth, leading to heavier infants and greater BMI by mid-childhood in contrast with children whose mothers were treated with insulin. Moreover, such patterns of low birth weight and postnatal catch-up growth have been listed to be related to adverse long-term cardio-metabolic outcomes.