Effects of Fasting on the Results of Fifty-Gram Test in GDM Screening

Document Type : Original Article


1 Assistant Professor of Obstetrics and Gynecology, Women’s Health Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

2 Associate Professor of Obstetrics and Gynecology, Women’s Health Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

3 Assistant Professor of Obstetrics and Gynecology, Fellowship of Perinatology, Imam Khomeini Hospital, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

4 Assistant Professor of Neonatology, Neonatal Subspecialist, Faculty of Medicine, Semnan University of Medical Sciences, Semnan, Iran.


Introduction: Gestational diabetes mellitus (GDM) refers to diagnosing of carbohydrate intolerance during pregnancy which may cause some serious fetal and maternal complications. GCT (fifty-gram glucose tolerance test) is the first test for GDM screening which is done without regarding of fasting condition. While prevalence of GDM is 2-5%, the result of this test is positive in 14-18% of pregnant women. Thus, those with positive results are screened by a three-hour hundred-gram glucose tolerance test (GTT). Execution of this test requires 8-14 hours fasting and four-times blood sampling in which the patient incurs a lot of time, cost and stresses. If GDM cases are reduced by execution of GTT after ten-hour fasting, a hundred-gram GTT is prevented in many patients. The aim of this survey is evaluation effects of fasting on results of fifty-gram oral glucose challenge test in GDM screening
Methods: A total of 130 pregnant women who met the inclusion criteria with gestational age of 24 to 32 weeks and were hospitalized in Imam Reza hospital from 2008 to 2009 participated in this study. They were randomly entered into fasting group (80 cases) or non-fasting group (50 cases). After one hour receiving fifty-gram oral glucose, blood sampling was taken from all of them. Then, the level of blood glucose was measured and compared between two groups by T test, Mann Whitney, Chi Square tests and SPSS software version 13. P<0.05 was determined significant.
Results: T-test evaluation shows no statistical significant relation between fasting status and the result of screening (P=0.89). But, based on Chi Square test, fasting and non-fasting group were statistically different in terms of mean blood glucose (P=0.03).
Conclusion: In GDM screening test, the mean level of blood glucose reduces in fasting status.


1. Metzger BE, Coustan DR. Summary and recommendations of the Fourth International Workshop-Conference on
Gestational Diabetes Mellitus. The Organizing Committee. Diabetes Care 1998 Aug;21(Suppl 2):B161-7.
2. American Diabetes Association. Gestational diabetes mellitus. American Diabetes Association: clinical practice
recommendations 2002. Diabetes Care 2002;25(Suppl 1):S94–6.
3. Kitzmiller JL. Cost analysis of diagnosis and treatment of gestational diabetes mellitus. Clin Obstet Gynecol
2000 Mar;43(1):140-53.
4. Magee MS,Walden CE, Benedetti TJ, Knopp RH. Influence of diagnostic criteria on the incidence of gestational
diabetes and prenatal morbidity. JAMA 1993 Feb 3;269(5):609-15.
5. Sweeney AT, Brown FM. Gestational diabetes mellitus. Clin Lab Med 2001 Mar;21(1):173-92.
6. Sermer M, Naylor CD, Gare DJ, Kenshole AB, Ritchie JW, Farine D, et al. Impact of increasing carbohydrate
intolerance on maternal- fetal outcomes in 3637 women without gestational diabetes. The Toronto Tri-Hospital
Gestational Diabetes Project. Am J Obstet Gynecol 1995 Jul;173(1):146-56.
7. Coustan DR. Gestational diabetes. Diabetes Care 1993;16(Suppl 3):8-15.
8. Tallarigo L, Giampietro O, Penno G, Miccoli R, Gregori G, Navalesi R. Relation of glucose tolerance to
complications of pregnancy in nondiabetic women. N Engl J Med 1986 Oct 16;315(16):989-92.
9. Langer O, Brustman L, Anyaegbunam A, Mazze R. The significance of one abnormal glucose tolerance test
value on adverse outcome in pregnancy. Am J Obstet Gynecol 1987 Sep;157(3):758-63.
10. Crowther CA, Hiller JE, Moss JR, McPhee AJ, Jeffries WS, Robinson JS. Effect of treatment of gestational
diabetes mellitus on pregnancy outcomes. N Engl J Med 2005 Jun 16;352(24):2477-86.
11. Eriksson UJ. Lifelong consequences of metabolic adaptations in utero? Diabetologia 1996 Sep;39(9):1123-5.
12. American Diabetic Association. Diagnosis and classification of diabetes mellitus. Diabetes Care 2006;29(Suppl
13. Report of a WHO Consultation. Definition, diagnosis and classification of diabetes mellitus and its
complications. Available at: http://whqlibdoc.who.int/hq/1999/ WHO_NCD_NCS_99.2.pdf. Accessed June 21,
14. Stamilio DM, Olsen T, Ratcliffe S, Sehdev HM, Macones GA. False-positive 1-hour glucose challenge test and
adverse perinatal outcomes. Obstet Gynecol 2004 Jan;103(1):148-56.
15. Jimenez-Moleon JJ, Bueno-Cavanillas A, Luna-del-Castillo Jde D, Garcia-Martin M, Lardelli-Claret P, GalvezVargas
R. Impact of different levels of carbohydrate intolerance on neonatal outcomes classically associated
with gestational diabetes mellitus. Eur J Obstet Gynecol Reprod Biol 2002 Apr 10;102(1):36-41.
16. Dudhbhai M, Lim L, Bombard A, Juliard K, Meenakshi B, Trachelenberg Y, et al. Characteristics of patients
with abnormal glucose challenge test and normal oral glucose tolerance test results: comparison with normal and
gestational diabetic patients. Am J Obstet Gynecol 2006 May;194(5):e42-45.
17. Ertunc D, Tok E, Dilek U, Pata O, Dilek S. The effect of carbohydrate intolerance on neonatal birth weight in
pregnant women without gestational diabetes mellitus. Ann Saudi Med 2004 Jul-Aug;24(4):280-3.
18. Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Rouse DJ, Spong CY. Williams obstetrics. 23rd ed. New
York: McGraw-Hill;2010:1169-87.
19. American Diabetes Association. Gestational diabetes mellitus. Definition, detection, and diagnosis. Diabetes
Care 2002;25:S94–S96. Available at: http://care.diabetesjournals.org/cgi/content/full/25/suppl_1/s94. Accessed
in 2005 (Sep 13).
20. Ayach W, Costa RAA, Calderon IMP, Rudge MVC. Comparison between 100-g glucose tolerance test and two
other screening tests for gestational diabetes: combined fasting glucose with risk factors and 50-g glucose
tolerance test. Sao Paulo Med J 2006 Jan 5;124(1):4-9.
21. Gestational diabetes mellitus. Diabetes Care 2003;26:S103-5.
22. American Diabetes Association. Gestational diabetes mellitus. Diabetes Care 1999;22(Suppl 1):S74-5.
23. Werner EF, Pettker CM, Zuckerwise L, Reel M, Funai EF, Henderson J, et al. Screening for gestational diabetes
mellitus: are the criteria proposed by the international association of the Diabetes and Pregnancy Study Groups
cost-effective? Diabetes Care 2012 Mar;35(3):529-35.
24. Poyhonen-Alho MK, Teramo KA, Kaaja RJ, Hiilesmaa VK. 50gram oral glucose challenge test combined with
risk factor-based screening for gestational diabetes. Eur J Obstet Gynecol Reprod Biol 2005 Jul 1;121(1):34-7.
25. Griffin ME, Coffey M, Johnson H, Scanlon P, Foley M, Stronge J, et al. Universal vs. risk factor-based
screening for gestational diabetes mellitus: detection rates, gestation at diagnosis and outcome. Diabet Med 2000
26. Rey E, Hudon L, Michon N, Boucher P, Ethier J, Saint-Louis P. Fasting plasma glucose versus glucose
challenge test: screening for gestational diabetes and cost effectiveness. Clin Biochem 2004 Sep;37(9):780-4.
27. Perucchini D, Fischer U, Spinas GA, Huch R, Huch A, Lehmann R. Using fasting plasma glucose
concentrations to screen for gestational diabetes mellitus: prospective population based study. BMJ 1999 Sep
28. Sacks DA, Greenspoon JS, Fotheringham N. Could the fasting plasma glucose assay be used to screen for
gestational diabetes? J Reprod Med 1992 Nov;37(11):907-9.
29. Agarwal MM, Hughes PF, Punnose J, Ezimokhai M. Fasting plasma glucose as a screening test for gestational
diabetes in a multi-ethnic, high-risk population. Diabet Med 2000 Oct;17(10):720-6.
30. Khan SH, Sadia F, Arshad H, Khalil A. Evaluation of fasting and random plasma glucose for diagnosis of
gestational diabetes. J Coll Physicians Surg Pak 2009 Nov;19(11):718-22.
31. Stuebe AM, Mantzoros C, Kleinman K, Gillman MW, Rifas-Shiman S, Seely EW, et al. Gestational glucose
tolerance and maternal metabolic profile at 3 years postpartum. Obstet Gynecol 2011 Nov;118(5):1065-73.
32. Retnakaran R, Shah BR. Abnormal screening glucose challenge test in pregnancy and future risk of diabetes in
young women. Diabet Med 2009 May;26(5):474-7.
33. Tarim E, Cok T, Iskender C. Can the 50-g glucose challenge test be important for subsequent pregnancies? J
Matern Fetal Neonatal Med 2012 Apr 25. [Epub ahead of print]