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Gestational Diabetes Mellitus

AMERICAN DIABETES ASSOCIATION

DEFINITION, DETECTION, AND DIAGNOSIS

DefinitionGestational diabetes mellitus (GDM) isdefined as any degree of glucose intoler-ance with onset or first recognition duringpregnancy (1). The definition applieswhether insulin or only diet modificationis used for treatment and whether or notthe condition persists after pregnancy. Itdoes not exclude the possibility that un-

recognized glucose intolerance may haveantedated or begun concomitantly withthe pregnancy.

 Approximately 7% of all pregnanciesare complicated by GDM, resulting inmore than 200,000 cases annually. Theprevalence may range from 1 to 14% of allpregnancies, depending on the populationstudied and the diagnostic tests employed.

Detection and diagnosisRisk assessment for GDM should be un-dertaken at thefirst prenatal visit.Women

with clinical characteristics consistentwith a high risk of GDM (marked obesity,personal history of GDM, glycosuria, or astrong family history of diabetes) shouldundergo glucose testing (see below) assoon as feasible. If they are found not tohave GDM at that initial screening, theyshould be retested between 24 and 28weeks of gestation. Women of averagerisk should have testing undertaken at24–28 weeks of gestation. Low-risk sta-tus requires no glucose testing, but thiscategory is limited to those women meet-

ing all of the following characteristics:

● AgeϽ25 years● Weight normal before pregnancy

● Member of an ethnic group with a lowprevalence of GDM

● No known diabetes in first-degree relatives● No history of abnormal glucose tolerance● No history of poor obstetric outcome

 A fasting plasma glucose level Ͼ126mg/dl (7.0 mmol/l) or a casual plasmaglucoseϾ200 mg/dl (11.1 mmol/l) meetsthe threshold for the diagnosis of diabe-tes, if confirmed on a subsequent day, andprecludes the need for any glucose chal-lenge. In the absence of this degree of hy-perglycemia, evaluationforGDM in womenwith average or high-risk characteristicsshould follow one of two approaches:

One-step approach: Perform a diagnos-tic oral glucose tolerance test (OGTT)without prior plasma or serum glucosescreening. The one-step approach may becost-effective in high-risk patients or pop-ulations (e.g., some Native-Americangroups).

Two-step approach: Perform an initialscreening by measuring the plasma or se-rum glucose concentration 1 h after a50-g oral glucose load (glucose challengetest [GCT]) and perform a diagnosticOGTT on that subsetof women exceedingthe glucose threshold value on the GCT.

 Whe n the two-step approa ch is em-ployed, a glucose threshold value Ͼ140mg/dl (7.8 mmol/l) identifies approxi-mately 80% of women with GDM, and theyield is further increased to 90% by usinga cutoff of Ͼ130 mg/dl (7.2 mmol/l).

 With either approach, the diagnosisof GDM is based on an OGTT. Diagnosticcriteria for the 100-g OGTT are derivedfrom the original work of O’Sullivan and

Mahan, modified by Carpenter and Cous-tan, and are shown in Table 1. Alterna-tively, the diagnosis can be made using a75-g glucose load and the glucose thresh-old values listed for fasting, 1 h, and 2 h(Table 2); however, this test is not as wellvalidated for detection of at-risk infants ormothers as the 100-g OGTT.

OBSTETRIC AND PERINATALCONSIDERATIONS — T h e p r e s -ence of fasting hyperglycemia (Ͼ105

mg/dl orϾ5.8 mmol/l) may be associatedwith an increase in the risk of intrauterinefetal death during the last 4–8 weeks of gestation. Although uncomplicated GDMwith less severe fasting hyperglycemia hasnot been associated with increased peri-natal mortality, GDM of any severity in-creases the risk of fetal macrosomia.Neonatal hypoglycemia, jaundice, poly-cythemia, and hypocalcemia may compli-cate GDM as well. GDM is associated withan increased frequency of maternal hy-pertensive disorders and the need for ce-

sarean delivery. The latter complicationmay result from fetal growth disordersand/or alterations in obstetric manage-ment due to the knowledge that themother has GDM.

Long-term considerations Women with GDM are at increased riskfor the development of diabetes, usuallytype 2, after pregnancy. Obesity and otherfactors that promote insulin resistance ap-pear to enhance the risk of type 2 diabetesafter GDM, while markers of islet cell–

directed autoimmunity are associatedwith an increase in the risk of type 1 dia-betes. Offspring of women with GDM areat increased risk of obesity, glucose intol-erance, and diabetes in late adolescenceand young adulthood.

THERAPEUTIC STRATEGIESDURING PREGNANCY 

Monitoring ● Maternal metabolic surveillance should

be directed at detecting hyperglycemia

● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

Therecommendations in this paper arebasedon theevidencereviewedin thefollowing publications: Reportof the expert committee on the diagnosis and classification of diabetes mellitus. Diabetes Care 21 (Suppl.1):S5–S19, 1998; and the Proceedings of the 4th International Workshop-Conference on Gestational Dia-betes Mellitus. Diabetes Care 21 (Suppl. 2):B1–B167, 1998.

Originally approved 1986. Most recent review/revision, 2000.Abbreviations: GCT, glucose challenge test; GDM, gestational diabetes mellitus; IFG, impaired fasting

glucose; IGT, impaired glucose tolerance; MNT, medical nutrition therapy; OGTT, oral glucose tolerancetest; SMBG, self-monitoring of blood glucose.

© 2004 by the American Diabetes Association.

P O S I T I O N S T A T E M E N T

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severe enough to increase risks to thefetus. Daily self-monitoring of bloodglucose (SMBG) appears to be superior

to intermittent of fice monitoring of plasma glucose. For women treatedwith insulin, limited evidence indicatesthat postprandial monitoring is supe-rior to preprandial monitoring. How-ever, the success of either approachdepends on the glycemic targets thatare set and achieved.

● Urine glucose monitoring is not usefulin GDM. Urine ketone monitoring maybe useful in detecting insuf ficient ca-loric or carbohydrate intake in womentreated with calorie restriction.

● Maternal surveillance should includeblood pressure and urine protein mon-itoring to detect hypertensive disor-ders.

● Increased surveillance for pregnanciesat risk for fetal demise is appropriate,particularly when fasting glucose lev-els exceed 105 mg/dl (5.8 mmol/l) orpregnancy progresses past term. Theinitiation, frequency, and specific tech-niques used to assess fetal well-beingwill depend on the cumulative risk thefetus bears from GDM and any othermedical/obstetric conditions present.

●

Assessment for asymmetric fetalgrowthby ultrasonography, particularly inearly third trimester, may aid in identi-fying fetuses that can benefit from ma-ternal insulin therapy (see below).

Management● All women with GDM should receive

nutritional counseling, by a registereddietitian when possible, consistent withthe recommendations by the AmericanDiabetes Association. Individualizationof medical nutrition therapy (MNT) de-

pending on maternal weight and heightis recommended. MNT should includethe provision of adequate calories andnutrients to meet the needs of preg-

nancy and should be consistent withthe maternal blood glucose goals thathave been established. Noncaloricsweeteners may be used in moderation.

● For obese women (BMI Ͼ30 kg/m2), a30 –33% calorie restriction (to ϳ25kcal/kg actual weight per day) has beenshown to reduce hyperglycemia andplasma triglycerides with no increase inketonuria (2). Restriction of carbohy-drates to 35– 40% of calories has beenshown to decrease maternal glucoselevels and improve maternal and fetal

outcomes (3).● Insulin is the pharmacologic therapy

that has most consistently been shownto reduce fetal morbidities when addedto MNT. Selection of pregnancies forinsulin therapy can be based on mea-sures of maternal glycemia with orwithout assessment of fetal growthcharacteristics. When maternal glucose

levels are used, insulin therapy is rec-ommended when MNT fails to main-tain self-monitored glucose at thefollowing levels:

Fasting plasma glucoseՅ105 mg/dl (5.8 mmol/l)

or1-h postprandial plasma glucoseՅ155 mg/dl (8.6 mmol/l)

or2-h postprandial plasma glucoseՅ130 mg/dl (7.2 mmol/l)

● Measurement of the fetal abdominalcircumference early in the third trimes-ter can identify a large subset of infantswith no excess risk of macrosomia inthe absence of maternal insulin ther-apy. This approach has been tested pri-marily in pregnancies with maternal

fasting serum glucose levels Ͻ105mg/dl (5.8 mmol/l).

● Human insulin should be used wheninsulin is prescribed, and SMBG shouldguide the doses and timing of the insu-lin regimen. The use of insulin analogshas not been adequately tested in GDM.

● Oral glucose-lowering agents have gen-erally not been recommended duringpregnancy. However, one randomized,unblinded clinical trial compared theuse of insulin and glyburide in womenwith GDM who were not able to meet

glycemic goals on MNT (4). Treatmentwith either agent resulted in similarperinatal outcomes. All patients werebeyond the first trimester of pregnancyat the initiation of therapy. Glyburide isnot FDA approved for the treatment of GDM and further studies are needed ina larger patient population to establishits safety.

Table 1—Diagnosis of GDM with a 100-g

oral glucose load

mg/dl mmol/l

Fasting 95 5.31-h 180 10.0

2-h 155 8.63-h 140 7.8

Two or more of the venous plasma concentrationsmust be met or exceeded for a positive diagnosis.The test should be done in the morning after anovernightfastof between 8 and14 h andafterat least3 days of unrestricteddiet(Ն150g carbohydrateperday) and unlimited physical activity. The subjectshould remain seated and should not smokethroughout the test.

Table 2—Diagnosis of GDM with a 75-g

oral glucose load

mg/dl mmol/l

Fasting 95 5.31-h 180 10.0

2-h 155 8.6Two or more of the venous plasma concentrationsmust be met or exceeded for a positive diagnosis.The test should be done in the morning after anovernightfast of between 8 and14 h andafter at least3 days of unrestricted diet (Ն 150 g carbohydrateper day) and unlimited physical activity. The subjectshould remain seated and should not smokethroughout the test.

Table 3—Criteria for the diagnosis of diabetes mellitus

Normoglycemia IFG and IGT Diabetes mellitus*

FPGϽ100 mg/dl FPG Ն100 mg/dl andϽ126 mg/dl (IFG)

FPGՆ126 mg/dl

2-h PG† Ͻ140 mg/dl 2-h PG†Ն140 mg/dl andϽ200 mg/dl (IGT)

2-h PG†Ն200 mg/dl

— — Symptoms of DM and casualplasma glucose

concentrationՆ200 mg/dl

DM, diabetes mellitus; FPG, fasting plasma glucose; 2-h PG, 2-h postload glucose. *In the absence of unequivocalhyperglycemia,a diagnosisof diabetes mustbe confirmedon a subsequentdayby any one ofthethree methods included in the chart. In clinical settings, the FPG test is greatly preferred because of ease of administration, convenience, acceptability to patients, and lower cost. Fasting is defined as no calorie intakefor at least 8 h. †This test requires the use of a glucose load containing the equivalent of 75 g anhydrousglucose dissolved in water.

Gestational Diabetes Mellitus

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● Programs of moderate physical exercisehave been shown to lower maternalglucose concentrations in women withGDM. Although the impact of exerciseon neonatal complications awaits rigor-ous clinical trials, the beneficial glucose-lowering effects warrant a recommen-dation that women without medical orobstetrical contraindications be en-couraged to start or continue a programof moderate exercise as a part of treat-ment for GDM.

● GDM is not of itself an indication forcesarean delivery or for delivery before38 completed weeks of gestation. Pro-longation of gestation past 38 weeks in-creases the risk of fetal macrosomiawithout reducing cesarean rates, so thatdelivery during the38th week is recom-mended unless obstetric considerations

dictate otherwise.● Breast-feeding, as always, should be en-

couraged in women with GDM.

LONG-TERM THERAPEUTICCONSIDERATIONS — Reclassifica-tion of maternal glycemic status should beperformed at least 6 weeks after deliveryand according to the guidelines of the“Report of the Expert Committee on theDiagnosis and Classification of Diabetes

Mellitus” (5). See Table 3 for diagnosticcriteria. If glucose levels are normal post-partum, reassessment of glycemia shouldbe undertaken at a minimum of 3-yearintervals. Women with IFG or IGT in thepostpartum period should be tested fordiabetes annually; these patients shouldreceive intensive MNT and should beplaced on an individualized exercise pro-gram because of their very high risk fordevelopment of diabetes. All patients withprior GDM should be educated regardinglifestyle modifications that lessen insulinresistance, including maintenance of nor-mal body weight through MNT and phys-ical activity. Medications that worseninsulin resistance (e.g., glucocorticoids,nicotinic acid) should be avoided if pos-sible. Patients should be advised to seekmedical attention if they develop symp-

toms suggestive of hyperglycemia. Educa-tion should also include the need forfamily planning to ensure optimal glyce-mic regulation from the start of any sub-sequent pregnancy. Low-dose estrogen-progestogen oral contraceptives may beused in women with prior histories of GDM, as long as no medical contraindi-cations exist.

Offspring of women with GDMshould be followed closely for the devel-

opment of obesity and/or abnormalities of glucose tolerance.

References

1. Metzger BE, Coustan DR (Eds.): Proceed-ings of the Fourth International Work-

shop-Conference on Gestational DiabetesMellitus. Diabetes Care 21 (Suppl. 2):B1–B167, 1998

2. Franz MJ,BantleJP, Beebe CA,Brunzell JD,Chiasson J-L, Garg A. Holzmeister LA,Hoogwerf B, Mayer-Davis E, Mooradian AD, Purnell JQ, Wheeler M: Evidence-based nutrition principles and recommen-dations for the treatment and prevention of diabetes and related complications (Tech-nical Review). Diabetes Care 25:148 –198,2002

3. Major CA, Henry MJ, De Veciana M, Mor-gan MA: The effects of carbohydrate re-striction in patients with diet-controlled

gestational diabetes. Obstet Gynecol 91:600 – 604, 1998

4. Langer L, ConwayDL, BerkusMD, XenakisEM-J, Gonzales O: A comparison of gly-buride and insulin in women with gesta-tional diabetes mellitus. N Engl J Med 343:1134 –1138, 2000

5. Expert Committee on the Diagnosis andClassification of Diabetes Mellitus: Reportof the Expert Committee on the Diagnosisand Classification of Diabetes Mellitus.Diabetes Care 20:1183–1197, 1997

Position Statement

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