title: Fasting blood glucose predicts response to extended-release metformin in gestational diabetes mellitus.
abstract: 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.
  
  
  OBJECTIVE
  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.
authors.affiliation: John Morris Diabetes Centre, Launceston General Hospital, Launceston, Tasmania, Australia. acorbould@yahoo.com
authors.forename: Anne
authors.initials: A
authors.lastname: Corbould
authors.forename: Fiona
authors.initials: F
authors.lastname: Swinton
authors.forename: Andrea
authors.initials: A
authors.lastname: Radford
authors.forename: Joanne
authors.initials: J
authors.lastname: Campbell
authors.forename: Sue
authors.initials: S
authors.lastname: McBeath
authors.forename: Amanda
authors.initials: A
authors.lastname: Dennis
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D003692:Delayed-Action Preparations; D016640:Diabetes, Gestational / Q000097:blood / Q000178:diet therapy / Q000188:drug therapy*; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007004:Hypoglycemic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D007328:Insulin / Q000627:therapeutic use; D008687:Metformin / Q000009:adverse effects / Q000627:therapeutic use*; D011237:Predictive Value of Tests; D011247:Pregnancy; D047928:Premature Birth / Q000209:etiology
chemical_list: D001786:Blood Glucose; D003692:Delayed-Action Preparations; D007004:Hypoglycemic Agents; D007328:Insulin; D008687:Metformin