This statement summarizes the current U.S. Preventive Services Task Force (USPSTF) recommendation on screening for gestational diabetes mellitus, and updates the 1996 recommendation contained in the Guide to Clinical Preventive Services, Second Edition1.
Summary of Recommendation
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Clinical Considerations Scientific Evidence Recommendations of Others References Members of the Task Force Contact the Task Force Available Products| Task Force Ratings Strength of Recommendations and Quality of Evidence |
Gestational diabetes mellitus is defined as glucose intolerance with onset or first detection during pregnancy.6,7 GDM occurs in 2-5 percent of all pregnancies, or approximately 135,000 cases annually in the United States.6 Major risk factors for developing GDM include increasing maternal age, family history of diabetes, history of GDM in a prior pregnancy, and increased pregravid BMI.8 The prevalence of GDM varies in direct proportion to the prevalence of type-2 diabetes in a given population or ethnic group.6 GDM is more common among African American, Hispanic, and American Indian women and less common among Asian women. Variations in screening practices and in other risk factors make it difficult to quantify the independent contribution of race and ethnicity to developing GDM.
Prevalence of GDM in women with defined low-risk factors, such as being of white ethnic origin, being younger than 25 years, and having a BMI of less than 25 kg/m2, ranges from 1.4 percent to 2.8 percent.9-14 The prevalence of GDM in women with defined high-risk factors, such as being older than 25 years, being obese, or having a family history of diabetes, ranges from 3.3 percent to 6.1 percent.11
GDM has been linked to increased maternal perinatal morbidity (resulting from an increase in cesarean deliveries and forceps or vacuum extraction, as well as third- and fourth-degree lacerations), principally through its association with fetal macrosomia.15-22
Macrosomia is associated with an increased risk for neonatal adverse effects, such as brachial plexus injuries (most of which are temporary) and clavicular fracture.17,21,23-24 Data on the overall impact of GDM screening and treatment on these outcomes is limited because most babies with macrosomia are born to mothers without GDM,15,25-29 and most cases of injuries related to shoulder dystocia occur in pregnancies with infants of normal birthweight. The relationship between GDM and adverse outcomes is further confounded by the fact that maternal obesity is an independent risk factor for many of the same outcomes.16,30,31 The tendency of clinicians to manage differently women who bear the diagnosis of GDM from those who do not may contribute to the observed increase in risk for cesarean delivery in women with GDM.4
Defining the performance characteristics of screening strategies for GDM is complicated by the lack of a universally accepted "gold standard" for diagnosis of GDM. Different diagnostic tests are used in North America and in Europe.4,32-33 Diagnostic criteria in the United States are based on a 100-g 3-h OGTT, but these criteria were originally developed for their ability to identify mothers at risk for developing diabetes, not those whose newborns were at risk for macrosomia or other complications. Expert groups have proposed different criteria for diagnosis based on the 3-h OGTT; although all the diagnostic criteria predict risk for macrosomia, evidence is weak to support any particular diagnostic standard for GDM. More liberal criteria increase the number of women diagnosed with GDM by more than 50 percent but may not reduce the prevalence of fetal macrosomia.32
Screening for GDM in North America is based on a 50-g 1-h GCT, usually performed during the 24th to 28th week of gestation. Two thresholds for an abnormal screen have been proposed by different experts:
Fewer than 1 in 5 women with a positive GCT will meet criteria for GDM on a full OGTT.35 The reliability of the GCT is questionable for one-third of women with GDM; in one study, screening performed on 2 successive days produced different results.14 Data to support specific timing for screening also are sparse. Women who develop GDM early in pregnancy are at higher risk for neonatal hypoglycemia and other GDM-related outcomes than are those who develop GDM later in pregnancy.36 Screening earlier in pregnancy detects fewer women with GDM, but identifies those at highest risk and allows for earlier intervention. Screening for GDM later in pregnancy detects a larger number of women with GDM, many of whom are at lower risk, but who would be treated for a shorter time.
No properly conducted randomized controlled trial (RCT) has examined the benefit of universal or selective screening for GDM compared with no screening. The only RCT that attempted to evaluate the effects of universal versus selective screening had important methodologic and analytic flaws. The differences in the timing of screening and the treatments in the study groups make it difficult to draw any conclusions about the benefits of screening.36 A retrospective analysis that found similar rates of macrosomia in screened and unscreened populations cannot rule out an effect of screening, because screened women may have been at higher risk for GDM than unscreened women, and the study may not have been large enough to detect a benefit.37 One well-conducted prospective cohort study suggests that screening and diagnosis can reduce macrosomia but that other health outcomes were not affected.38
A proposed benefit of screening is that the diagnosis of GDM may lead to interventions to reduce the risk for mothers of developing diabetes later. The USPSTF found no evidence to determine whether diagnosis leads to important lifestyle changes for such women; many of the proposed interventions (e.g., weight loss and exercise) could be recommended for these women on other grounds, independent of their risk for developing diabetes.
Data on the effects of diet therapy alone for treating GDM are limited. An overview of four RCTs found no significant benefits of diet, but the studies were small and had other limitations.39 Randomized trials have shown that adding insulin to diet therapy, compared with diet therapy alone, can reduce the incidence of macrosomia, but they have not shown improvement in other important maternal or perinatal outcomes such as cesarean delivery rates, birth trauma, or perinatal mortality.40-42 These trials are hampered by small size and lack of power for detecting small changes in more important health outcomes.
Even if screening and treatment are effective, the benefits of widespread screening as a means for preventing birth trauma due to macrosomia are likely to be small. Modeling done for the USPSTF, which assumed that treatment with insulin would reduce the risk of having an infant with macrosomia in mothers with GDM by 75 percent, calculated that nearly 7,000 women at high risk, and 9,000 women at average risk, would need to be screened to prevent 1 case of brachial plexus injury. Although serious, 80 percent of such injuries resolve within the first year.
Data are insufficient to make conclusive statements about possible harms of screening for GDM. Screening generates frequent false-positive results requiring the inconvenience of further testing. One study raises the possibility that the diagnosis of GDM may influence provider decisionmaking and could increase cesarean delivery rates, despite measures taken to decrease the risk for fetal macrosomia.31 This study evaluated the rates of cesarean delivery related to birth weight and GDM. In this study, women who were diagnosed and treated for GDM had substantially higher rates of cesarean delivery (34 percent) than controls (20 percent) even though rates of macrosomia were comparable. In a second control group, in which clinicians were not informed that women had borderline GDM, rates of macrosomia were higher than rates among treated women, yet cesarean delivery rates were slightly lower (30 percent) and other birth outcomes (lacerations) were comparable.
The data are limited and mixed as to whether the diagnosis of GDM adversely affects women's perception of their health during pregnancy.43-46 Limited data suggest that the diagnosis of GDM may have long-term effects on women's perception of their health.45,47 Potential adverse effects of treatment strategies for GDM include increased maternal starvation ketosis resulting from aggressive glycemic-lowering therapy, and infants who are small for their gestational age. Even uncommon risks are potentially important since nearly 100 women need to be treated with insulin to prevent 1 case of brachial plexus injury due to macrosomia. However, the magnitude of these potential harms has not been evaluated and quantified.48,49
In the absence of adequate evidence to determine whether selective or universal screening is effective in improving important health outcomes, reliable estimates of cost-effectiveness of screening are not possible. The cost-effectiveness of screening depends greatly on the unproven assumption that screening will significantly lower rates of cesarean section and birth trauma. No studies include all relevant cost information related to screening for GDM, including the costs of screening and diagnostic tests, costs of various treatments, and the costs of complications. Reliable estimates of the costs of GDM for women who are not screened are not available.
The American Diabetes Association recommends screening all women at risk for GDM. The ADA considers women to be at risk for GDM unless they are younger than 25 years, have normal body weight, are not a member of a high-risk ethnic group, have no first-degree relatives with diabetes, and have no personal history of glucose intolerance or poor obstetrical outcome.5 A 2001 Practice Bulletin of the American College of Obstetricians and Gynecologists (ACOG) recommends a similar risk-based approach, but notes that since only a small percentage of patients meet criteria for low risk, universal 50-g 1-h GCT screening may be a more practical approach.6 The Canadian Task Force on Preventive Health Care concluded in 1991 that the available evidence did not support a recommendation for or against universal screening for GDM.50
1. U.S. Preventive Services Task Force. Screening for gestational diabetes. In: Guide to Clinical Preventive Services, 2nd ed. Washington, DC: Office of Disease Prevention and Health Promotion; 1996:193-208.
2. Brody SC, Harris RP, Lohr KN. Screening for gestational diabetes: A summary of the evidence for the U.S. Preventive Services Task Force. Obstet Gynecol 2003;101:380-92.
3. Brody SC, Harris R, Whitener BL, et al. Screening for Gestational Diabetes. Systematic Evidence Review No. 26 (Prepared by RTI-University of North Carolina at Chapel Hill Evidence-Based Practice Center under Contract No. 290-97-011). Rockville, MD: Agency for Healthcare Research and Quality. May 2002. (Available at: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat3.chapter.4471).
4. WHO Consultation: Definition, diagnosis and classification of diabetes mellitus and its complications: report of a WHO Consultation. Part 1: diagnosis and classification of diabetes mellitus. Geneva, WHO/NCD/NCS/99.2, World Health Org., 1999.
5. American Diabetes Association. Gestational diabetes mellitus. Diabetes Care 2002;25(Suppl 1):S94-6.
6. American College of Obstetricians and Gynecologists Practice Bulletin. Clinical management guidelines for obstetrician-gynecologists. Number 30, September 2001. Obstet Gynecol 2001;98(3):525-38
7. Magee M, Walden C, Benedetti T, Knopp R. Influence of diagnostic criteria on the incidence of gestational diabetes and perinatal morbidity. JAMA 1993;269(5):609-15.
8. Solomon C, Willet W, Carey V, et al. A prospective study of pregravid determinants of gestational diabetes mellitus. JAMA 1997;278(13):1078-83.
9. Moses R, Moses J, Davis W. Gestational diabetes: do lean young Caucasian women need to be tested? Diabetes Care 1998;21(11):1803-6.
10. Lavin JP, Barden TP, Miodovnik M. Clinical experience with a screening program for gestational diabetes. Am J Obstet Gynecol 1981;141(5):491-4.
11. Marquette G, Klein V, Niebyl J. Efficacy of screening for gestational diabetes. Am J Perinatol 1985;2(1):7-9.
12. Lemen PM, Wington TR, Miller-McCarthy AJ, Cruikshank DW. Screening for gestational diabetes mellitus in adolescent pregnancies. Am J Obstet Gynecol 1998;178(6):1251-6.
13. Southwick RD, Wigton TR. Screening for gestational diabetes mellitus in adolescent Hispanic Americans. J Reprod Med 2000;45(1):31-4.
14. Harlass F, Brady K, Read J. Reproducibility of the oral glucose tolerance test in pregnancy. Am J Obstet Gynecol 1991;164:564-8.
15. Mondalou H, Dorchester W, Thorosian A, Freeman R. Macrosomia—maternal, fetal, and neonatal implications. Obstet Gynecol 1980;55(4):420-4.
16. Spellacy W, Miller S, Winegar A, Peterson P. Macrosomia—maternal characteristics and infant complications. Obstet Gynecol 1985;66:158-61.
17. Berard J, Dufour P, Vinatier D, et al. Fetal macrosomia: risk factors and outcome. A study of the outcome concerning 100 cases >4500 g. Eur J Obstet Gynecol Reprod Biol 1998;77(1):51-9.
18. Menticoglou S, Manning F, Morrison I, Harman C. Must macrosomic fetuses be delivered by cesarean section? A review of outcome for 786 babies greater than or equal to 4,500 grams. Aust N Z J Obstet Gynaecol 1992;32(2):100-3.
19. Rouse D, Owen J. Prophylactic cesarean delivery for fetal macrosomia diagnosed by means of ultrasonography—A Faustian bargain? Am J Obstet Gynecol 1999;181(2):332-8.
20. Lazer S, Biale Y, Mazor M, Lewenthal H, Insler V. Complications associated with the macrosomic fetus. J Reprod Med 1986;31:501-5.
21. Lipscomb K, Gregory K, Shaw K. The outcome of macrosomic infants weighing at least 4500 grams: Los Angeles County + University of Southern California experience. Obstet Gynecol 1995;85(4):558-64.
22. el Madany A, Jallad K, Radi F, el Hamdan H, O'deh H. Shoulder dystocia: anticipation and outcome. Int J Gynaecol Obstet 1990;34:7-12.
23. Morrison J, Sanders J, Magann E, Wiser W. The diagnosis and management of dystocia of the shoulder. Surg Gynecol Obstet 1992;175(6):515-22.
24. Hardy A. Birth injuries of the brachial plexus: incidence and prognosis. J Bone Joint Surg Br 1981;63-B:98-101.
25. American College of Obstetricians and Gynecologists. Diabetes and pregnancy. Washington, DC. American College of Obstetricians and Gynecologists. Technical Bulletin No. 200, 1994.
26. Gross T, Sokol R, Williams T, Thompson K. Shoulder dystocia: a fetal-physician risk. Am J Obstet Gynecol 1987;156(6):1408-18.
27. McFarland L, Raskin M, Daling J, Benedetti T. Erb/Duchenne's palsy: a consequence of fetal macrosomia and method of delivery. Obstet Gynecol 1986;68(6):784-8.
28. Sandmire H, O'Halloin T. Shoulder dystocia: its incidence and associated risk factors. Int J Gynaecol Obstet 1988;26:65-73.
29. Okun N, Verma A, Mitchell B, Flowerdew G. Relative importance of maternal constitutional factors and glucose intolerance of pregnancy in the development of newborn macrosomia. J Matern Fetal Med 1997;6(5):285-90.
30. Lucas M, Lowe T, Bowe L, McIntire D. Class A1 gestational diabetes: A meaningful diagnosis? Obstet Gynecol 1993;82(2):260-65.
31. Naylor C, Sermer M, Chen E, Sykora K. Cesarean delivery in relation to birth weight and gestational glucose tolerance: pathophysiology or practice style? Toronto Tri-Hospital Gestational Diabetes Investigators. JAMA 1996;275(15):1165-70.
32. Metzger B, Coustan D. Summary and recommendations of the Fourth International Workshop-Conference pm gestational diabetes mellitus. Diabetes Care 1998;21(Suppl 2):B161-7.
33. Schwartz M, Ray W, Lubarsky S. The diagnosis and classification of gestational diabetes mellitus: is it time to change our tune? Am J Obstet Gynecol 1999;180(6):1560-71.
34. Sermer M, Naylor C, Gare D, et al. Impact of time since last meal on the gestational glucose challenge test. The Toronto Tri-Hospital Gestational Diabetes Project. Am J Obstet Gynecol 1994;171(3):607-16.
35. Bartha J, Martinez-Del-Fresno P, Comino-Delgado R. Gestational diabetes mellitus diagnosed during early pregnancy. Am J Obstet Gynecol 2000;182(2):346-50.
36. Griffin M, 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(1):26-32.
37. Santini DL, Ales KL. The impact of universal screening for gestational glucose intolerance on outcome of pregnancy. Surg Gynecol Obstet 1990;170:427-36.
38. Garner P, Okun N, Keely E, et al. A randomized controlled trial of strict glycemic control and tertiary level obstetric care versus routine obstetric care in the management of gestational diabetes: A pilot study. Am J Obstet Gynecol 1997;177(1):190-5.
39. Walkinshaw S. Dietary regulation for 'gestational diabetes' 2000. Cochrane Database of Systemic Reviews 2000;(2):CD000070.
40. Kjos SL, Schaefer-Graf U, Sardesi S, et al. A randomized controlled trial using glycemic plus fetal ultrasound parameters versus glycemic parameters to determine insulin therapy in gestational diabetes with fasting hyperglycemia. Diabetes Care 2001;24:1904-10.
41. Langer O, Anyaegbunam A, Brustman L, Divon M. Management of women with one abnormal oral glucose tolerance test value reduces adverse outcome in pregnancy. Am J Obstet Gynecol 1989;161:593-9.
42. Persson B, Strangenberg M, Hansson U, Norlander E. Gestational diabetes mellitus (GDM) comparative evaluation of two treatment regimens, diet versus insulin and diet. Diabetes 1985;11:101-5.
43. Kerbel D, Glazier R, Holzapfel S, Yeung M, Lofsky S. Adverse effects of screening for gestational diabetes: a prospective cohort study in Toronto, Canada. J Med Screen 1997;4(3):128-32.
44. Sjogren B, Robeus N, Hansson U. Gestational diabetes: a case-control study of women's experience of pregnancy, health and the child. J Psychosomatic Res 1994;38(8):815-22.
45. Langer N, Langer O. Emotional adjustment to diagnosis and intensified treatment of gestational diabetes. Obstet Gynecol 1994;84(3):329-34.
46. Spirito A, Williams C, Ruggiero L, Bond A, McGarvey S, Coustan D. Psychological impact of the diagnosis of gestational diabetes. Obstet Gynecol 1989;73(4):562-6.
47. Feig D, Chen E, Naylor C. Self-perceived health status of women three to five years after the diagnosis of gestational diabetes: A survey of cases and matched controls. Am J Obstet Gynecol 1998;178(2):386-93.
48. Langer O, Levy J, Brustman L, Anyaegbunam A, Merkatz R, Divon M. Glycemic control in gestational diabetes mellitus—how tight is tight enough: small for gestational age vs. large for gestational age? Am J Obstet Gynecol 1989;161:646-53.
49. Knopp RH, Magee MS, Raisys V, Benedetti T, Bonet B. Hypocaloric diets and ketogenesis in the management of obese gestational diabetic women. J Am Coll Nutr 1991;10:649-67.
50. Canadian Task Force on the Periodic Health Examination. Screening for gestational diabetes mellitus. Can Med Assoc J 1992;147:435-43.
Members of the U.S. Preventive Services Task Force are Alfred O. Berg, M.D., M.P.H., Chair, USPSTF (Professor and Chair, Department of Family Medicine, University of Washington, Seattle, WA); Janet D. Allan, Ph.D., R.N., Vice-chair, USPSTF (Dean, School of Nursing, University of Maryland Baltimore, Baltimore, MD); Paul Frame, M.D. (Tri-County Family Medicine, Cohocton, NY, and Clinical Professor of Family Medicine, University of Rochester, Rochester, NY); Charles J. Homer, M.D., M.P.H.* (Executive Director, National Initiative for Children's Healthcare Quality, Boston, MA); Mark S. Johnson, M.D., M.P.H. (Chair, Department of Family Medicine, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark, NJ); Jonathan D. Klein, M.D., M.P.H. (Associate Professor, Department of Pediatrics, University of Rochester School of Medicine, Rochester, NY); Tracy A. Lieu, M.D., M.P.H.* (Associate Professor, Department of Ambulatory Care and Prevention, Harvard Pilgrim Health Care and Harvard Medical School, Boston, MA); Cynthia D. Mulrow, M.D., M.Sc.* (Clinical Professor and Director, Department of Medicine, University of Texas Health Science Center, San Antonio, TX); C. Tracy Orleans, Ph.D. (Senior Scientist and Senior Program Officer, The Robert Wood Johnson Foundation, Princeton, NJ); Jeffrey F. Peipert, M.D., M.P.H.* (Director of Research, Women and Infants' Hospital, Providence, RI); Nola J. Pender, Ph.D., R.N.* (Professor Emeritus, University of Michigan, Ann Arbor, MI); Albert L. Siu, M.D., M.S.P.H. (Professor of Medicine, Chief of Division of General Internal Medicine, Mount Sinai School of Medicine, New York, NY); Steven M. Teutsch, M.D., M.P.H. (Senior Director, Outcomes Research and Management, Merck & Company, Inc., West Point, PA); Carolyn Westhoff, M.D., M.Sc. (Professor of Obstetrics and Gynecology and Professor of Public Health, Columbia University, New York, NY); and Steven H. Woolf, M.D., M.P.H. (Professor, Department of Family Practice and Department of Preventive and Community Medicine, Fairfax, VA).
* Member of the USPSTF at the time this recommendation was finalized.
Address correspondence to: Chair, U.S. Preventive Services Task Force; c/o Project Director, USPSTF; 540 Gaither Road; Rockville, MD 20850; E-mail: uspstf@ahrq.gov.
This recommendation and rationale statement, plus complete information on which this statement is based, including evidence tables and references, are available on the USPSTF Web site at http://www.preventiveservices.ahrq.gov.
Recommendations made by the USPSTF are independent of the U.S. Government. They should not be construed as an official position of AHRQ or the U.S. Department of Health and Human Services.
Source: This recommendation first appeared in Obstet Gynecol 2003;101(2):393-5.
Current as of February 2003
Internet Citation:
U.S. Preventive Services Task Force. Screening for Gestational Diabetes Mellitus: Recommendations and Rationale. February 2003. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/3rduspstf/gdm/gdmrr.htm
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