Gestational diabetes mellitus (GDM) develops during pregnancy and is usually diagnosed following assessment for risk factors followed by elevated plasma glucose levels on testing.
Goal of therapy is to achieve maternal glucose levels that are as close to normal as possible in order to avoid fetal macrosomia and complications.
Initial therapy for gestational diabetes is usually dietary modification, unless women have marked elevated glucose levels, which will require immediate initiation of insulin (with or without metformin). If acceptable glucose levels cannot be maintained with diet alone, therapy is typically stepped up to add metformin and then insulin.
Maternal postnatal testing for diabetes or impaired glucose tolerance is performed at 6 to 13 weeks following delivery and annually thereafter.
The risk for recurrence of GDM in subsequent pregnancies or progression to type 2 diabetes is high and all women with a history of GDM should be offered additional screening for cardiovascular risk factors as well as support for weight management and diabetes prevention.
GDM is defined as hyperglycaemia in pregnancy that is below diagnostic thresholds for diabetes. The precise diagnostic criteria remain a subject of debate. Guidelines differ in their recommendations on the stage of pregnancy when GDM can be diagnosed. The World Health Organization criteria state that it can be diagnosed at any time in pregnancy, whereas the American Diabetes Association limits the definition to hyperglycaemia that is first detected after the first trimester. In the UK, the National Institute for Health and Care Excellence does not specify a timeframe but recommends that women should be assessed for risk factors at their booking appointment and those with risk factors should be tested for GDM, with the timing of the testing dependent on which risk factor(s) are present.
In practice, GDM is most often recognised at 24 to 28 weeks of gestation, based on an abnormal glucose tolerance test.
This topic covers women whose hyperglycaemia is first detected during pregnancy. For management of pregnancy in women with pre-existing diabetes, see our topics 'Type 1 diabetes in adults' and 'Type 2 diabetes in adults'.
History and exam
Eleanor Scott, BM, BS, MD, FRCP
Professor of Medicine (Diabetes and Maternal Health)
Leeds Institute of Cardiovascular and Metabolic Medicine
Leeds Centre for Diabetes and Endocrinology
ES has received honoraria from Abbott Diabetes Care and Lilly Diabetes for giving talks, workshops, and advisory panels. ES has received research grant funding from MRC, NIHR, and Diabetes UK.
Rebecca Spencer, MBChB, BSc, MRCOG, PhD
NIHR Clinical Lecturer in Obstetrics and Gynaecology
University of Leeds
Dr Scott and Dr Spencer would like to gratefully acknowledge Dr Ellen W. Seely, Dr Chloe Zera, Dr Jeremy Soule and Dr Leonard E. Egede, previous contributors to this topic.
EWS and CZ declare that they have no competing interests. JS has undertaken research support and speakers' bureau activity for Novartis, Bristol Myers Squibb, Astra Zeneca, and Sanofi-Aventis. LEE is an author of a number of references cited in this topic.
Helen Murphy, MBBch, BAO, FRACP, MD
Clinical Professor in Medicine (Diabetes and Antenatal Care)
University of East Anglia
HM sits on the Medtronic (insulin pump and CGM manufacturer) European scientific advisory board. HM has received research support (CGM sensors and insulin pumps) at reduced cost from Medtronic, Dexcom, and Johnson & Johnson. MH has contributed to educational events sponsored by NovoNordisk, Medtronic, Dexcom, and Abbott Diabetes Care.
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