Gestational Diabetes MellitusBackground/IntroductionGestational diabetes (GDM) is defined as glucose intolerance of variable degree with onset or first recognition during the present pregnancy. It can be screened by drawing a 1-hour glucose level following a 50-g glucose load, but is definitively diagnosed only by an abnormal 3-hour OGTT following a 100-g glucose load. GDM is a form of hyperglycemia. In general, hyperglycemia results from an insulin supply that is inadequate to meet tissue demands for normal blood glucose regulation. Studies conducted during late pregnancy, when, as discussed below, insulin requirements are high and differ only slightly between normal and gestational diabetic women, consistently reveal reduced insulin responses to nutrients in women with GDM (Xiang, 1999, 848-54: Kautzky, 1997, 1717-23).
Studies conducted before or after pregnancy, when women with prior GDM are usually more insulin resistant than normal women, often reveal insulin responses that are similar in the 2 groups or reduced only slightly in women with prior GDM (Catalano, 1999, 903-16; Homko, 2001, 568-73; Osei, 1998, 1250-57). However, when insulin levels and responses are expressed relative to each individual’s degree of insulin resistance, a large defect in pancreatic β cell function is a consistent finding in women with prior GDM (Kautzky, 1997, 1717-23; Ryan, 1995, 506-12; Buchanan, 2001, 989-93). Etiology of Diabetes Mellitus For insulin dependent diabetes, the cumulative risk for siblings of diabetic patient is 6-10 per cent versus 0.6 per cent for the general population.
Regarding the effect of parental genes, the offspring of women with type 1 diabetes have a lower risk of disease (21%) than the off-springs of men with type I diabetes (6.1%). The reason for this disparity is unknown.
The incidence of IDDM peaks at about 11-13 years of age. There is a striking seasonal variation in the incidence in older children and adolescents, with lowest rates in spring and summer. NIDDM: The familial clustering of non-insulin dependents suggests a strong genetic component of the disease. The cumulative risk for type II diabetes in siblings of diabetes patient is 10-33 per cent versus 5 per cent for the general population. Offspring of women with type II diabetes have a two to three-fold greater risk of developing diabetes than offspring of men with the disease.
The exact mode of inheritance is not known. Investigations in a number of developing countries have shown urban-rural differences of varying degree with generally higher rates in urban area. The growth and maturation of the fetus are closely associated with the delivery of maternal nutrients, particularly glucose. This is most crucial in the third trimester and is directly related to the duration and degree of maternal glucose elevation. Thus, the negative impact is as highly diverse as the variety of carbohydrate intolerance that women bring to pregnancy.
For the mother with GDM there is a higher risk of hypertension, preeclampsia, urinary tract infections, cesarean section, and future diabetes. Many of the problems associated with overt diabetic pregnancies can be seen in infants of gestational diabetic pregnancies, such as macrosomia, neural tube defects, neonatal hypoglycemia, hypocalcemia, hypomagnsemia, hyperbilirubinemia, birth trauma, prematurity syndromes, and subsequent childhood and adolescent obesity.