Fasting Plasma Glucose is not Sufficient to Detect Ongoing Glucose Intolerance after Pregnancy Complicated by Gestational Diabetes

Abstract

Aims: Women who develop diabetes during pregnancy are at significant risk of developing Type 2 diabetes later in life, and “should be offered blood glucose testing … to exclude persisting hyperglycaemia” after delivery. New UK guidelines now recommend that this is done by measurement of fasting blood glucose, rather than an oral glucose tolerance test (OGTT). Our study aims to establish whether assessment by fasting blood glucose gives equivalent results to an OGTT.

Methods: Retrospective data were obtained from four centres in the West Midlands, UK, who performed a postnatal OGTT on 470 women during a 12-month period. All centres used a 75 g, 2-h protocol.

Results: 28 of 470 (6.0%) women had diabetes mellitus after testing of fasting plasma glucose. After OGTT, 70 women (14.9%) were found to have impaired glucose tolerance (IGT), and 10 further cases of diabetes were detected (overall prevalence of DM 8.1%). Of the 400 women with normal fasting plasma glucose. After OGTT, 70 women (14.9%) were found to have impaired glucose tolerance (IGT), and 10 further cases of diabetes were detected (overall prevalence of DM 8.1%). Of the 400 women with normal fasting plasma glucose (≤ 6.0 mmol/l), 55 were found to have impaired glucose tolerance and 4 had overt diabetes. In all, 26% of women with diabetes were missed by FPG.

Conclusion: Fasting plasma glucose alone does not allow detection of IGT, and misses a substantial proportion of women with Type 2 diabetes. Recognition of ongoing IGT or DM is important in identifying women who may benefit from lifestyle modification, and who may need early intervention in subsequent pregnancies. Our results suggest that OGTT should be the investigation of choice in the postnatal assessment of women who have had GDM.

Key words

gestational diabetes - post-partum - glucose tolerance test

References

• 1 Kitzmiller JL, Dang-Kilduff L, Taslimi MM. Gestational diabetes after delivery.  Diabetes Care. 2007;  30 S225-S235
• 2 Kim C, Newton KM, Knopp RH. Gestational Diabetes and the Incidence of Type 2 Diabetes.  Diabetes Care. 2002;  25 1862-1868
• 3 Ben-Haroush A, Yogev Y, Hod M. Epidemiology of gestational diabetes mellitus and its association with Type 2 diabetes.  Diabetic Medicine. 2003;  21 103-113
• 4 NICE guidelines . Diabetes in pregnancy: Management of diabetes and its complications from preconception to the post-natal period. March 2008; 
• 5 Holt RIG, Goddard JR, Clarke P. et al . A fasting plasma glucose is useful in determining which women with gestational diabetes should undergo a post-natal glucose tolerance test.  Diabetic Medicine. 2003;  20 594-598
• 6 American Diabetes Association. . Diagnosis and Classification of Diabetes Mellitus.  Diabetes Care. 2006;  29 S43-S48
• 7 The HAPO Study Cooperative Research Group. . Hyperglycemia and Adverse Pregnancy Outcomes.  NEJM. 2008;  358 1991-2002
• 8 ONS data. . http://www.statistics.gov.uk
• 9 Costa A, Carmona F, Martinez-Roman S. et al . Post-partum reclassification of glucose tolerance in women previously diagnosed with gestational diabetes.  Diabetic Medicine. 2000;  17 595-598
• 10 Bartha JL, Martinez-del-Fresno P, Comino-Delgado R. Postpartum metabolism and autoantibody markers in women with gestational diabetes mellitus diagnosed in early pregnancy.  Am J Obstet Gynecol. 2001;  184 965-970
• 11 Knowler WC, Barrett-Connor E, Fowler SE. et al . Reduction in the incidence of Type 2 Diabetes with lifestyle intervention or metformin.  NEJM. 2002;  346 393-403
• 12 Gillies CL, Abrams KR, Lambert PC. et al . Pharmacological and lifestyle interventions to prevent or delay type 2 diabetes in people with impaired glucose tolerance: systematic review and meta-analysis.  BMJ. 2007;  334 299-302

Correspondence