Gestational diabetes
The concept of gestational diabetes, actually meaning hyper-glycemia due to the pregnancy itself but in practice defined as 'carbohydrate intolerance of varying severity with onset or first recognition during pregnancy,' is also recent.15 In the very first recorded case Bennewitz, in 1823, considered that the diabetes was actually a symptom of the pregnancy, and as the symptoms and the glycosuria disappeared after at least two successive pregnancies he had some evidence to support his views.16 That lesser degrees of maternal hyperglycemia were also a risk to pregnancy outcome dates back to studies in the 1940s in the USA17,18 and Scotland,19 which showed increased perinatal mortality some years before the recognition of clinical diabetes mellitus. This led to the term prediabetes in pregnancy, and to poorly defined concepts of temporary and latent diabetes. The first prospective study of carbohydrate metabolism in pregnancy was established in Boston in 1954, using a 50 g, 1 h screening test, which has subsequently been widely adopted in the USA.20 O'Sullivan21 first used the name 'gesta-tional diabetes' in 1961, following the term metagestational diabetes used by Dr JP Hoet in 1954 after his early studies in Louvain, Belgium.22 At that time the US emphasis was on establishing criteria for the 100 g oral glucose tolerance test in pregnancy as an index of the subsequent risk of the mother developing established diabetes, and the well-known O'Sullivan criteria were derived on this basis.23 At about the same time, Mestman in southern California, began to identify the very considerably increased perinatal mortality associated with abnormal oral glucose tolerance in the obstetric population of Los Angeles County Hospital, which then comprised > 60% Latino mothers with the rest African-American and only a few Caucasian.24 Subsequent studies in many parts of the world have extended the recognition of what has now become, in some places, an epidemic of hyperglycemia in pregnancy. Jorgen Pedersen also used the term gestational diabetes in his monograph in 1967, but preferred to so classify a mother only after delivery, when he had demonstrated that her abnormal glucose tolerance in pregnancy had actually returned to normal postpartum; this rigorous definition has proved too difficult to achieve in practice.25,26 The true definition of hyperglycemia in pregnancy judged by the internationally acceptable 75 g oral glucose tolerance test awaits the results of the large Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study.27 The enthusiasm of the team at Northwestern University, Chicago, led by Norbert Freinkel and subsequently by Boyd Metzger has ensured that the concept of gestational diabetes is now firmly imprinted on the obstetric mind, as well as having established a major place as an epi-demiological tool to study not only the immediate outcome of pregnancy but also the long-term effects on both mother and baby of the relatively short phase of hyperglycemia during the latter part of the pregnancy.
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