Gestational Diabetes Mellitus

Gestational Diabetes Mellitus (GDM) is diabetes or impaired glucose tolerance of variable severity with the first recognition during pregnancy. Screening is now part of routine antenatal care in many settings in developed countries. There are several screening tests, but the most common is the oral glucose tolerance test, which tests the blood glucose level in order to initiate treatment for the prevention of complications in pregnant women and their infants. There is substantial debate surrounding the most suitable screening tests, the effectiveness of treatment in averting adverse mother and infant outcomes in women with mild to moderate glucose intolerance, the possibility of causing anxiety, and the potentially adverse effects of a “high risk” label in pregnancy for those with Gestational Diabetes Mellitus. A systematic review of the literature was conducted in order to examine the psychosocial effects of screening for Gestational Diabetes Mellitus. There was inconsistency in the results due to the variety of designs and methods used, and the outcomes assessed. Most studies found no significant differences between women with Gestational Diabetes Mellitus and controls regarding mental health (anxiety and depression), concerns for the health of the newborn, and attitudes towards screening for Gestational Diabetes Mellitus. However, women who were found to have Gestational Diabetes Mellitus or who had false-positive results were more likely to worry about their own health than those whose screening test was negative or were not tested. Women with Gestational Diabetes Mellitus were more likely than controls to rate their health as poor rather than excellent. The long term consequences of these concerns are not known. Many studies were methodologically weak, with low recruitment rates, large losses to follow up, recall bias, turf effects, and the use of unstandardised measures. More studies in this field are needed since there is little research investigating the psychosocial implications of screening for GDM.

Gestational diabetes mellitus (GDM) is controversial in terms of management and outcomes among women who are initially found to have glucose intolerance during pregnancy (Khandelwal, 1999; Scott, 2002). There is debate regarding appropriate screening and diagnostic criteria for elevated blood glucose during pregnancy, the best screening methods to be applied (Rumbold and Crowther, 2001; Scott, 2002), and also regarding the benefits and potential harm of screening programs (Brody, 2003). However, screening for GDM is becoming part of routine antenatal care in many parts of the world. An important aspect of the evaluation of any screening program is its impact on those who are screened (Rumbold and Crowther, 2001).

What is GDM ?

GDM is identification of diabetes, or impaired glucose tolerance (IGT) of variable severity first recognized during pregnancy (American Diabetes Association, 2004). GDM exists when there is an increase in blood glucose levels (Scott, 2002) because of a disorder of carbohydrate metabolism (Metzger and Coustan, 1998). This disorder may affect the fetus and newborn as well as the mother if untreated (Jones and Stone, 1998).
GDM is associated with a disorder of insulin resistance, insulin action and insulin secretion during pregnancy. Thus, GDM is classified as Type-2 diabetes. Some women with GDM go on to develop Type-2 diabetes in later life (Daniells, 2003; Khandelwal, 1999).

Diagnosis of GDM

Diagnosis is a confirmation of GDM in people with a positive screening test. There are several tests for the diagnosis of GDM, but the most commonly test is OGTT. Usually OGTT is performed in women at an increased risk. For example, in women with previous GDM, the OGTT is performed early after diagnosis of gestation (Bartha, 2003) or when GDM is identified on a screening test.

For the diagnostic test, many hospitals in Australia use a 75g OGTT. Fewer hospitals use a 50g OGTT and 100g OGTT (Rumbold and Crowther, 2001). The requirement of elevated blood glucose levels also differs between Australia hospitals (the requirement ranges between 1-3 elevated blood samples). There is also variety in the management for GDM. Regimens include self-monitoring of blood glucose level, laboratory monitoring of blood glucose level, exercise, diet control, and a combination of diet and insulin therapy (Rumbold and Crowther, 2001).

Glucose load and timing also vary in different places around the world (Scott, 2002). In some countries, where large glucose loads are used, women may feel uncomfortable using 75 g glucose-loads (Scott, 2002). Moreover, the test results are less satisfactory with this higher load than with lower loads (Scott, 2002). There are also side effects with the high concentrated glucose load, for example nausea, vomiting and bloating may affect the test results (Murphy, 1994; Shushan and Samueloff, 1998). Different timing of assessment also influences the results of the test.

What are the Risk Factors of GDM ?

Risk factors for GDM may be classified into two types: modifiable and unmodifiable (Dornhorst and Rossi, 1998). Risk factors over which a woman has no control include maternal age of above 25 years, ethnicity (e.g. Aboriginal Canadians, African-American, Asian, Hispanic, Indian, Native American and Pima Indians, and probably other indigenous groups), weight prior to pregnancy, parity, and personal and family history of diabetes. Risk factors which are potentially modifiable include obesity (a body mass index (BMI) more than 27 kg/m2) and further weight gain (American Diabetes Association, 2004; Jones and Stone, 1998; Ostlund, 2003; Scott, 2002). BMI is calculated by dividing weight in kilograms by the height in meters squared.

Other risk factors include a prior low birth weight baby (less than 2,500 g), impaired glucose tolerance, impaired fasting glucose, poor diet, sedentary life style, smoking, hypertension and other cardiovascular risk factors, and genetic problems (e.g. glucokinase and hepatic nuclear disorder) (Capes and Anand, 2001; Scott, 2002).

Treatment of GDM

There is disagreement about the treatment of GDM, and particularly about the management of minor degrees of glucose elevation or glucose intolerance (Scott, 2002). There is more than one treatment for women with GDM, including diet control, insulin therapy, and exercise. An appropriate diet may accomplish physiologic glucose homeostasis. If dietary modification fails to achieve this, then insulin therapy is begun (Brody, 2003). Catalano (2003) suggested that insulin therapy is one of the most suitable treatments. It is claimed that this regimen can reduce fetal macrosomia, but more studies to show the effect on maternal and neonatal health outcomes are needed (Brody, 2003). Association between perinatal mortality and morbidity and abnormal GTT or GDM has been overemphasized (Hunter and Keirse, 1989). Hunter and Keirse (1989) found no evidence that insulin therapy improves neonatal outcome and decreases macrosomia in the infant.