- Despite lower average birth weight, children whose mothers were treated with metformin for gestational diabetes mellitus (GDM) show accelerated postnatal growth.
Why this matters
- Patterns of low birth weight and postnatal catch-up growth have been linked to adverse long-term cardiometabolic outcomes.
- Metformin is increasingly used for GDM as a cheaper alternative to insulin.
- Meta-analysis of 28 studies including 3976 mothers randomly assigned to metformin or insulin for GDM treatment with reported offspring outcomes.
- Funding: author funding from the British Heart Foundation, Medical Research Council.
- Neonates born to metformin-treated mothers weighed 107.7 g less than those of insulin-treated mothers (P=.005) and were 40% less likely to have macrosomia (OR, 0.59; P<.001>
- At ages 18 months-2 years, children of metformin-treated mothers weighed 440 g more than those of insulin-treated mothers (P=.03).
- At ages 5-9 years, BMI was 0.78 kg/m2 higher in metformin vs insulin group (P=.005).
- No height differences.
- Only 2 studies followed up to midchildhood.
- Possible recall bias with later follow-up.
- Uncertainty about whether lower birth weight represents lower lean mass or fetal adiposity.
- Bias risk in many studies.
- Women who required both metformin and insulin usually excluded, potentially skewing results.
- Heterogeneity across study GDM criteria.