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METFORMIN is increasingly used in clinical practice for the treatment of gestational diabetes mellitus GDM. However, its safety and long-term effects on fetuses exposed to metformin in uterus remain controversial.

STUDY Bao and colleagues have studied safety and long-term effects of the use of metformin since fetuses exposed to metformin in uterus remain controversial.
PUBLISHED This study is now reported in the Journal Maternal & Fetal Neonatal Med. 2019 Sep 26:1-13.

METHODOLOGY was a 24 studies (17 randomised controlled trials for quantitative analyses: n=2828; 7 studies for qualitative synthesis) met eligibility criteria after a systematic search PubMed, Embase, and the Cochrane database, for randomized controlled trials comparing metformin with insulin.

RESULTS showed:
Metformin vs insulin therapy for GDM was associated with a reduced risk for:
*pregnancy-induced hypertension (risk ratio [RR], 0.64; 95% CI, 0.44-0.95; P=.03);
*large gestational age babies (RR, 0.82; 95% CI, 0.68-0.99; P=.04);
*macrosomia (RR, 0.63; 95% CI, 0.45-0.90; P=.01);
*neonatal hypoglycaemia (RR, 0.72, 95% CI, 0.59-0.88; P=.001); and
*neonatal intensive care unit admission (RR, 0.74; 95% CI, 0.58-0.94; P=.01).
Metformin use did not increase the risk for:
*premature delivery (RR, 1.28; 95% CI, 0.95-1.73; P=.11);
*pre-eclampsia (RR, 0.89; 95% CI, 0.65-1.21; P=.45);
*caesarean delivery (RR, 0.94; 95% CI, 0.85-1.04; P=.20); and
*small for gestational age babies (RR, 0.99; 95% CI, 0.69-1.42; P=.95).

The long-term results seemed to have no adverse effect, but the information was still limited.

According to this review, metformin may have potential benefits for pregnant women and newborns with no obvious adverse effects. However, even more studies are needed to provide evidence for the future use of metformin.