Current Management of Gestational Diabetes Mellitus

Guido Menato; Simona Bo; Anna Signorile; Marie-Laure Gallo; Ilenia Cotrino; Chiara Botto Poala; Marco Massobrio

Disclosures

Expert Rev of Obstet Gynecol. 2008;3(1):73-91. 

In This Article

Abstract and Introduction

Diabetes mellitus is one of the most common medical complications of pregnancy; gestational diabetes mellitus (GDM) accounts for approximately 90-95% of all cases. GDM is defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy. It has been demonstrated that good metabolic control maintained throughout pregnancy can reduce maternal and fetal complications in diabetes. Diet is the mainstay of treatment in GDM, but physical activity is a helpful adjunctive therapy when euglycemia is not achieved by diet alone. When diet and exercise fail to maintain euglycemia, exogenous insulin is used and the new insulin currently available on the market may help. Traditionally, insulin therapy has been considered the gold standard for management. The American College of Obstetricians and Gynecologists and the American Diabetes Association do not currently recommend oral hypoglycemic agents as a treatment for GDM. Concerns regarding safety demand further well-designed studies.

Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance of variable severity with onset or first recognition during pregnancy.[1] The prevalence of GDM varies from 1 to 14%, in direct proportion to the prevalence of Type 2 diabetes in a given population or ethnic group.[2]

Unmodifiable known risk factors associated with GDM include age, genetic background, ethnicity and number of previous pregnancies; recently, a short stature has been identified as an independent variable. A modifiable known risk factor is obesity; in addition, lack of exercise, dietary fat and lifestyle habits that adversely influence insulin resistance, such as smoking and certain drugs, could have an important influence.[3]

Many tests for GDM have been described, but a distinction is generally made between screening tests and diagnostic tests. In general, screening and diagnostic tests are performed between 24 and 28 weeks, because at this point in gestation the diabetogenic effect of pregnancy is manifest.

Several different screening tests are in use. It seems to be inefficient to use risk factors as a screening test to identify subjects to submit to diagnostic test.[4]

Currently, the most utilized screening test is oral glucose challenge test with 50 g of glucose. The American Diabetes Association (ADA) recommends a cut-off value after 1 h of either 140 mg/dl (7.8 mmol/l), which is said to identify 80% of women with GDM, or 130 mg/dl (7.2 mmol/l), which should identify 90%.[5] Problems have also been reported for the glucose challenge test: there are many false-positives and sensitivity is only 86 at best.[6] Other screening tests include fasting blood glucose and random blood glucose. Generally used cut-off values are 126 mg/dl (7.0 mmol/l) for fasting blood glucose and 200 mg/dl (11.1 mmol/l) for random blood glucose.[7]

The diagnostic test for GDM has always been the 100 gram 3 h oral glucose tolerance test (OGTT). Two abnormal values are needed for the diagnosis of GDM.[8] Reproducibility has been reported to be 78% at best. At present, the most commonly used OGTT internationally is the 75 g glucose solution. This is the test recommended by the WHO and it is used in Europe. In the USA, the 100-g OGTT is still predominantly used. Different cut-off values are in use for the OGTT 100 g and 75 g ( Table 1 ).

The Hyperglycemia and Adverse Pregnancy Outcome study will provide data that will foster the development of criteria for the diagnosis of GDM that are based on perinatal outcomes.

GDM has short- and long-term implications both for the mother and child. Hyperglycemia remains a major cause of maternal and fetal morbidity. Pregnant women who do not meet the criteria for GDM may still have glucose-mediated macrosomia, an adverse pregnancy outcome (stillbirth, birth trauma, cesarean section, pre-eclampsia, respiratory distress, hypoglycemia, hyperbilirubinemia, polycythemia, hypocalcemia, increased neonatal intensive care unit admissions) and neonatal adiposity with its long-term sequelae including childhood obesity and diabetes.[1]

Both Type 2 diabetes and GDM are heterogeneous disorders whose pathophysiology is characterized by peripheral insulin resistance and declining ß-cell function. Both clinical entities are seen as the same disease with different names, representing a continuum of glucose tolerance deterioration.

The strategies and techniques for the management of GDM during pregnancy have greatly improved through the past two decades; new insulin therapies are now available and the diabetic patients' self-monitoring of blood glucose is widely incorporated in care plans. The aim of this review is to review international guidelines regarding the management of GDM and to propose possible new therapies.

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