Table 4.

Current guideline recommendations for use of metformin in gestational diabetes.

Guidelines	Recommendation
American Congress of Obstetricians and Gynecologists (ACOG), 2017 [99]	Insulin is first-line therapy if glycemic control is not attained with nonpharmacological treatment. Consider metformin if patient cannot take or declines insulin, but counsel about risk of placental cross-over and lack of long-term studies. Glyburide should not be used [43].
ADA Standards of Care, 2017 [100]	While metformin is associated with a lower risk of neonatal hypoglycemia and less maternal weight gain, long-term studies of oral antidiabetics are lacking and women should be informed that metformin crosses the placenta.
International Federation of Gynecology and Obstetrics (FIGO), 2015 [101]	If lifestyle modification alone fails to achieve glucose control, insulin, glyburide and metformin are safe and effective treatment options during second and third trimesters. Glyburide is inferior to both insulin and metformin, while metformin (plus insulin when required) performs slightly better than insulin. Insulin should be considered as the first-line treatment in women with GDM who are at high risk of failing on OAD therapy, including some of the following factors: Diagnosis of diabetes < 20 weeks of gestation Need for pharmacological therapy at <30 weeks Fasting plasma glucose > 110 mg/dL 1-hour postprandial glucose > 140 mg/dL Pregnancy weight gain > 12 kg
UK NICE guidelines, 2015 [102]	Metformin is used if glycemic targets are not attained with lifestyle modification within 1–2 weeks and insulin is used if metformin is not tolerated or acceptable to patient. Insulin should be immediately commenced if FPG ≥ 126 mg/dL or if FPG 108–125 mg/dL and there are complications such as macrosomia or hydramnios. Glyburide is considered if patient refuses insulin and cannot tolerate metformin.
Endocrine Society, 2015 [103]	Metformin can be considered in women who decline or cannot use insulin or glyburide and are not in the first trimester. Glyburide is considered a suitable alternative to insulin in women who fail to achieve glycemic control with lifestyle modification, except for those with diagnosis before 25 weeks of gestation and FPG > 110 mg/dL.
WINGS (Women in India with GDM Strategy) guidelines, 2015 [104]	There is some evidence metformin and glyburide are safe in pregnancy. However, they cross the placenta and long-term safety data are not available. If pregnant woman is already on metformin, it may be continued during pregnancy. Metformin may be used if insulin is not available, not practical or refused by the woman.
International Diabetes Federation, 2009 [105]	If glucose targets are not met within 1–2 weeks of lifestyle modification, start glucose-lowering medication. Insulin is the treatment of choice but there is now adequate evidence to consider the use of metformin and glyburide in women who have been informed of the possible risks. Combination therapy has not been specifically studied.

FPG, fasting plasma glucose; GDM, gestational diabetes; OAD, oral antidiabetic drugs.