Intended for healthcare professionals

Analysis Too Much Medicine

Gestational diabetes: new criteria may triple the prevalence but effect on outcomes is unclear

BMJ 2014; 348 doi: (Published 11 March 2014) Cite this as: BMJ 2014;348:g1567
  1. Tim Cundy, professor1,
  2. Evan Ackermann, general practitioner23,
  3. Edmond A Ryan, professor, division of endocrinology and metabolism3
  1. 1Department of Medicine, Faculty of Medical and Health Sciences, University of Auckland, New Zealand
  2. 2Condamine Medical Centre, Warwick, Queensland, Australia
  3. 3Department of Medicine, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
  1. Correspondence to: E A Ryan edmond.ryan{at}
  • Accepted 11 February 2014

Summary box

  • Clinical contextMild gestational diabetes is associated with perinatal morbidity

  • Diagnostic changeInternational recommendation to move from dual step testing to reliance on a single abnormal glucose value in an oral glucose tolerance test with reduced thresholds

  • Rationale for changeAn observational study showed that any degree of impaired glucose regulation in pregnancy is associated with adverse outcomes

  • Leap of faithReducing mildly raised blood glucose concentrations will improve outcomes for mother and baby

  • Effect on prevalence—Nearly 1 in 5 pregnancies will be identified as being affected by gestational diabetes: a 2-3-fold increase over existing levels of 2-6%

  • Evidence of overdiagnosis—Despite increased diagnosis there is no evidence from randomised controlled clinical trials that outcomes are improved

  • Harms from overdiagnosis—Many more women will experience medicalisation of their pregnancy with increased intervention

  • Limitations—Maternal obesity and excess weight gain in pregnancy are associated with gestational diabetes; both affect birth weight and other more serious pregnancy outcomes. The importance of mild hyperglycaemia is unknown

  • Conclusion—We need to understand better how to identify high risk pregnancies, incorporating other important factors in addition to glucose concentration

Maternal obesity, excess maternal weight gain during pregnancy, and gestational diabetes are all associated with large for gestational age infants and other adverse outcomes. With obesity being a major risk factor for gestational diabetes (diabetes first recognised in pregnancy), the increasing incidence of the condition is unsurprising. Treatment of obesity during pregnancy has disappointingly little effect on the numbers of babies born large for gestational age, but treatment of gestational diabetes is more successful. This has led to an emphasis on diagnosing and treating gestational diabetes, but do the recently proposed diagnostic criteria1 that triple its prevalence make sense? Is it good clinical care, or yet another example of overdiagnosis? …

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