American Journal of Epidemiology Vol. 152, No. 11 : 1015-1016
Copyright © 2000 by The Johns Hopkins University School of Hygiene and Public Health
ORIGINAL CONTRIBUTIONS |
Invited Commentary: Prenatal Glucose Screening and Gestational Diabetes
From the Department of Maternal and Child Health, School of Public Health, Rosenau Hall, CB#7400, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7400. (Correspondence to Dr. Pierre Buekens at this address (e-mail: Pierre_Buekens{at}UNC.EDU)).
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Screening for gestational diabetes has been widely recommended in the United States (1
). However, this relative consensus is not shared by everyone (2–5). One difficulty is that gestational diabetes is not a disease per se. It is an abnormal laboratory value, defined as glucose intolerance first detected during pregnancy. Furthermore, the criteria for glucose intolerance vary (1). There is reasonably good evidence that gestational diabetes is associated with fetal macrosomia (high birth weight) and with an increased risk of onset of diabetes in later life (6). However, the latter is probably also true for glucose intolerance occurring in nonpregnant women and in men and thus is not specific to gestational diabetes (4).
Screening for gestational diabetes is relevant only if treatment has an impact on perinatal or long-term outcomes. Ideally, evidence of such an impact should be derived from randomized controlled trials. A meta-analysis of trials on dietary regulation for gestational diabetes included four studies involving 612 women (7). The trials were small, and their quality was not ideal. No statistically significant differences were detected for fetal macrosomia (odds ratio = 0.78, 95 percent confidence interval: 0.45, 1.35) and cesarean sections (odds ratio = 0.97, 95 percent confidence interval: 0.65, 1.44). In addition to diet, treatment of gestational diabetes may involve insulin therapy (1, 8). Overtreatment of gestational diabetes could be detrimental, for example, by inducing fetal growth retardation (9). The impact of screening and treatment of gestational diabetes on onset of diabetes in later life is unknown.
In this issue of the Journal, Wen et al. (10) show that discontinuation of universal screening in one region of Canada had no impact on the rates of fetal macrosomia. While this study was based mostly on an ecologic design, it has the strength of being population-based. The results strongly suggest that screening for gestational diabetes has little or no impact on perinatal outcomes.
Wen et al. (10) also observed that increased screening for gestational diabetes identified cases of decreased severity. This finding suggests that additional cases of gestational diabetes identified by universal screening are mild. In the absence of evidence that universal screening makes an impact, identification of nonsevere cases is probably irrelevant. Selective rather than universal screening has been increasingly proposed. The American Diabetes Association, which recommended universal screening during the time period covered by Wen et al.'s study, now favors a slightly more selective approach (11). The Fourth International Workshop-Conference on Gestational Diabetes Mellitus endorsed this recommendation in 1997 (12). However, the selective screening strategy they proposed exempts only 10 percent of the population from screening (13). A slightly different strategy proposed by the Toronto Trihospital Gestational Diabetes Project group allowed a 35 percent reduction in the number of screening tests (14). The American College of Obstetricians and Gynecologists stated that, depending on the care setting and population, either universal or selective screening can be used (15). The US Preventive Services Task Force recently noted the absence of data to support screening (16).
Advocates of universal screening could argue that a selective strategy recommended by The American College of Obstetricians and Gynecologists in 1986 missed 35 percent of the "cases" while saving only $32 per case diagnosed (17). Also, a randomized controlled trial recently compared universal and selective screening and concluded that universal screening is superior (18). However, the results of this trial are difficult to interpret because the randomization technique was not optimal, and the analysis was not conducted on the basis of intention to treat.
There is an urgent need for large randomized controlled trials on screening for gestational diabetes. Individual randomization of pregnant women might be difficult, but randomization of providers or prenatal clinics should be feasible. Such trials would have been difficult to organize a decade ago, when the consensus in favor of universal screening was strong. The consensus is now eroding, and Wen et al.'s study (10) further challenges screening for gestational diabetes. We are now close to equipoise, the point at which opinions in favor and against an intervention are balanced enough to make trials warranted and feasible.
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REFERENCES |
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Kjos SL, Buchanan TA. Gestational diabetes mellitus. N Engl J Med 1999;341:1749–56.
[Free Full Text] -
Ecker JL, Mascola MA, Riley LE. Gestational diabetes. (Letter). N Engl J Med 2000;342:896–7.
[Free Full Text] -
Jarrett RJ. Should we screen for gestational diabetes? BMJ 1997;315:736–7.
[Free Full Text] -
Griffiths M. Debate over screening for gestational diabetes. Screening should take place only in context of good quality controlled trials. (Letter). BMJ 1998;316:861.
[Free Full Text] - Ray J. Debate over screening for gestational diabetes: evidence from randomised controlled trial is needed. (Letter). BMJ 1998:316:861.
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Soares J de AC, Dornhorstt A, Beard RW. The case for screening for gestational diabetes. BMJ 1997;315:737–9.
[Free Full Text] - Walkinshaw SA. Dietary regulation for ‘gestational diabetes" (Cochrane Review). In: The Cochrane Library. Issue 4. Oxford, England: Update Software, 1999.
- Langer O. Management of gestational diabetes. Clin Obstet Gynecol 2000;43:106–15.[Web of Science][Medline]
- Langer O, Levy J, Brustman L, et al. Glycemic control in gestational diabetes mellitus–how tight is tight enough: small for gestational age versus large for gestational age? Am J Obstet Gynecol 1989;161:646–53.[Web of Science][Medline]
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Wen SW, Liu S, Kramer MS, et al. Impact of prenatal glucose screening on the diagnosis of gestational diabetes and on pregnancy outcomes. Am J Epidemiol 2000;152:1009–14.
[Abstract/Free Full Text] - Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 1997;20:1183–97.[Web of Science][Medline]
- Metzger BE, Coustan DM. Summary and recommendations of the Fourth International Workshop-Conference on Gestational Diabetes Mellitus. The Organizing Committee. Diabetes Care 1998;21(suppl 2):B161–7.
- Danilenko-Dixon DR, Van Winter JT, Nelson RL, et al. Universal versus selective gestational diabetes screening: application of 1997 American Diabetes Association recommendations. Am J Obstet Gynecol 1999;181:798–802.[Web of Science][Medline]
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Naylor CD, Sermer M, Chen E, et al. Selective screening for gestational diabetes mellitus. N Engl J Med 1997;337:1591–6.
[Abstract/Free Full Text] - Guidelines for perinatal care. 4th ed. Elk Grove Village, IL: American Academy of Pediatrics, 1997.
- US Preventive Services Task Force. Screening for diabetes mellitus. In: Guide to clinical preventive services. 2nd ed. Baltimore, MD: Williams & Wilkins, 1996:193–208.
- Coustan DR, Nelson C, Carpenter MW, et al. Maternal age and screening for gestational diabetes: a population-based study. Obstet Gynecol 1989;73:557–61.[Web of Science][Medline]
- Griffin ME, Coffey M, Johnson H, et al. Universal vs. risk factor-based screening for gestational diabetes mellitus: detection rates, gestation at diagnosis and outcome. Diabet Med 2000;17:26–32.[Web of Science][Medline]
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Related articles in Am. J. Epidemiol.:
- Impact of Prenatal Glucose Screening on the Diagnosis of Gestational Diabetes and on Pregnancy Outcomes
- Shi Wu Wen, Shiliang Liu, Michael S. Kramer, K. S. Joseph, Cheryl Levitt, Sylvie Marcoux, and Robert M. Liston
Am. J. Epidemiol. 2000 152: 1009-1014.[Abstract] [FREE Full Text]
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