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Fasting blood glucose predicts response to extended-release metformin in gestational diabetes mellitus

journal contribution
posted on 2023-05-18, 01:17 authored by Anne CorbouldAnne Corbould, Swinton, F, Radford, A, Campbell, J, McBeath, S, Dennis, A

Background: Metformin is increasingly accepted as an alternative to insulin therapy in gestational diabetes mellitus (GDM). The Metformin in Gestational Diabetes (MiG) trial reported similar pregnancy outcomes for metformin versus insulin; however, supplemental insulin was required in 46% of women on metformin.

Aims: We aimed to identify predictors of response to metformin monotherapy in women with GDM attending a general hospital antenatal clinic. Methods We offered extended-release metformin to women diagnosed with GDM (ADIPS 1998 criteria) at ≥24 weeks of gestation. If glucose targets were not achieved (≤5.0 mmol/L fasting, ≤6.7 mmol/L two-h post-meal), women were changed to insulin. We carried out an audit to determine characteristics of metformin responders versus nonresponders.

Results: Twenty-five women chose initial metformin therapy; 16 (64%) achieved satisfactory glycaemic control (responders). Nine women (36%) were changed to insulin: seven due to inadequate control (nonresponders) and two had metformin intolerance. Fasting glucose at oral glucose tolerance test (OGTT) was significantly lower in metformin responders versus nonresponders; two-h glucose and BMI did not differ. Ninety-three percent of women with fasting glucose ≤5.2 mmol/L responded to metformin: conversely, at fasting glucose >5.2 mmol/L, 33% responded (P = 0.005). Neonatal outcomes were similar in metformin responders and nonresponders, women who chose initial insulin therapy (n = 25), or were diet-controlled (n = 21).

Conclusions: In women with GDM, fasting glucose on OGTT predicted response to metformin: at fasting glucose ≤5.2 mmol/L, the probability of response was 93%. Antenatal clinics should determine locally relevant predictors of response to metformin in women with GDM.


Publication title

Australian and New Zealand Journal of Obstetrics and Gynaecology








Tasmanian School of Medicine


Royal Australian N Z College Obstetricians & Gynecologists

Place of publication

254-260 Albert St, East Melbourne, Australia, Vic, 3002

Rights statement

Copyright 2012 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

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Socio-economic Objectives

Clinical health not elsewhere classified

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