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Pathophysiology of Gestational Diabetes Mellitus:

It is just to remember that “Pathophysiology” refers to the study of alterations in normal
body function (physiology and biochemistry) which result in disease. E.g. changes in the
normal thyroid hormone level causes either hyper or hypothyroidism. Changes in insulin
level as a decrease in its blood level or a decrease in its action will cause hyperglycemia and
finally diabetes mellitus.
Scientists agreed that gestational diabetes mellitus (GDM) is a condition in which women
without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy.
From our experience most women with GDM in the developing countries are not aware of
the symptoms (i.e., the disease will be symptomless). While some of the women will have
few symptoms and their GDM is most commonly diagnosed by routine blood examinations
during pregnancy which detect inappropriate high level of glucose in their blood samples.
GDM should be confirmed by doing fasting blood glucose and oral glucose tolerance test
(OGTT), according to the WHO diagnostic criteria for diabetes.
A decrease in insulin sensitivity (i.e. an increase in insulin resistance) is normally seen
during pregnancy to spare the glucose for the fetus. This is attributed to the effects of
placental hormones. In a few women the physiological changes during pregnancy result in
impaired glucose tolerance which might develop diabetes mellitus (GDM). The prevalence
of GDM ranges from 1% to 14% of all pregnancies depending on the population studied and
the diagnostic tests used. Although the majority of women with GDM return to normal
glucose tolerance immediately after delivery, a significant number will remain diabetic or
continue to have impaired glucose tolerance (IGT).
To understand how gestational diabetes occurs, it is necessary to understand the normal
physiological metabolism of glucose during pregnancy and the physiological changes –
mainly the endocrine changes during pregnancy in the feto-placental unit, which might
explain the development of insulin resistance and GDM.