Is it all about the sugar?
Gestational diabetes mellitus (GDM) is defined as glucose intolerance first recognized in the current pregnancy (1), and it affects ∼5–7% of all pregnancies (2). Recently, it was demonstrated in both randomized and cohort studies (3,4) that lack of treatment for GDM is associated with increased risk of serious perinatal morbidities. Although the consequences of poorly controlled GDM are evident, no consensus exists on either diagnostic criteria or metabolic aims in controlling GDM.
Traditionally, GDM is considered as a disorder primarily of carbohydrate metabolism; thus, blood glucose levels have become the main “key player” for monitoring and directing treatment during pregnancy. This focus on glycemic metabolism ignores the role of other potential fetal fuels such as proteins and lipids in the pathophysiology of GDM.
In any disease, understanding normality is necessary before defining goals for treatment. The normal physiology of carbohydrates, proteins, and lipids during pregnancy may serve as the basis for defining metabolic goals in diabetic pregnancy. Nevertheless, only scarce data exist regarding the normal physiology of glucose in nondiabetic pregnancy; furthermore, even less is understood regarding lipid or protein metabolism and other factors.
In this review, we will mainly focus on the glycemic profile in normal pregnancy and in GDM. In addition, the role of other nutrients and metabolic factors will be reviewed.
PATHOPHYSIOLOGY OF GDM—
Normal pregnancy has been characterized as a “diabetogenic state” due to change in the pattern of insulin secretion and sensitivity, resulting in increased postprandial glucose and insulin response in late pregnancy. During the first trimester and early in the second trimester, an increase in insulin sensitivity occurs mainly due to the relatively higher levels of estrogen; however, in the late second and early third trimesters, there is reduced sensitivity to insulin action. Human placental lactogen, leptin, prolactin, and cortisol are involved in these changes. …