Gestational Diabetes, screening, diagnosis and prognosis

University dissertation from Department of Obstetrics and Gynecology, Lund University

Abstract: Gestational diabetes (GD) is still a nonentity disease. There is no worldwide consensus how to define it or whether it is harmful to the woman or fetus. Therefore, from an ethical point of view, it is uncertain whether one should try to identify it. Since 1991, all pregnant women in Lund are offered a 75g oral glucose tolerance test (OGTT) at 27 – 28 weeks of pregnancy. In Sweden, the definition of GD is a 2-hour glucose value in capillary whole blood, at a 75g OGTT, of at least 9.0 mmol/l. In the materials from Lund, the upper 2 standard deviation limit in the distribution of 2-hour glucose values at OGTT is 8.3 mmol/l. Increased rates of Caesarean section and infant macrosomia were found even in the “sub GD” region (7.8 mmol/l – 8.9 mmol/l), suggesting that the limit of 7.8 mmol/l for impaired glucose tolerance, set by World Health Organisation, is more relevant from a clinical point of view. The Swedish Medical Birth Registry was used to identify 3,958 women with pregnancies complicated by GD in 1987–92. Their previous pregnancy outcomes were compared with those of 7,916 controls without a diagnosis of GD. A significantly increased risk of previous intrauterine death (OR 1.56) was found. Many of the GD women probably had an undetected GD in the previous pregnancy. The 8,684 children born in 1987–97 to women with GD in Sweden were significantly more often hospitalised during their first decade of life than the 1,213,957 controls but less often than the 3,874 children to women with pregestational diabetes. Congenital defects, neurological problems, accidents, and infections were the reasons for the increased hospital care rate in both groups. The increased rate of accidents may be due to neurological damage and it can be speculated that increased glucose values during pregnancy may contribute to infant brain damage. All women with GD in Lund, 1.2 % of all pregnant women, were offered another OGTT one year post partum. Then, 9.2% had diabetes mellitus (2 hour glucose value > 11.0 mmol/l) and another 21.8% had impaired glucose tolerance (7.8–11.0 mmol/l). No specific symptoms or factors were found, except the 2hour glucose value at the diagnostic OGTT, which could predict future development of diabetes. Thorough information and guidance to individuals at the risk of developing diabetes may lower their risk to develop diabetes mellitus and its complications. Today the diagnosis of diabetes mellitus type 2 is often not made until complications have occurred. Then the diabetes may have been undetected for several years.

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