Introduction
Gestational diabetes mellitus (GDM) developed into a worldwide major concern due to its increasing prevalence and clinical implications1. A variety of adverse perinatal outcomes, including macrosomia, shoulder dystocia, neonatal respiratory and metabolic disorders, and cesarean deliveries2 are associated with high maternal blood glucose levels. The long-term detrimental effects of GDM on metabolic function in adulthood have also been investigated and established.3
Detection of GDM is generally based on a two-step approach. The first step (glucose challenge test, GCT) is utilized to screen pregnant women and detect those at high risk for GDM by having the subjects consume 50 g of glucose and sampling their blood for glucose 1 hour later. Women whose glucose levels meet or exceed the screening threshold are then subjected to a 3-hour diagnostic oral glucose tolerance test (OGTT) consisting of a total of 100 g 4. Whether one or two abnormally high values in the OGTT results define GDM is still under debate5. While some suggest that a single abnormal value is associated with increased risk of large-for-gestational age (LGA) infants6, cesarean delivery, pre-eclampsia7 and increased risk of Type-2 diabetes later in life, others dispute these associations. 8,910,11. A recent systematic review concluded that hyperglycemia-related adverse perinatal outcomes are similarly found among women with both one or two abnormal OGTT values12.
The finding of hypoglycemia three hours after consuming 100 g of glucose is not uncommon and may present with dizziness, nausea, tachycardia, and sweating13. Clinical experience led us to the impression that women with one abnormal high value in the OGTT and hypoglycemia in the 180-min value have a more pronounced insulin resistance. Our search of the literature for studies assessing the clinical implications of such hypoglycemia on glucose control and perinatal outcome among women with a single abnormally high value yielded no results. In light of the unassessed clinical significance of such a common occurrence, we were motivated to investigate this clinical quandary. We hypothesized that a 3-hour hypoglycemia finding may reflect impaired insulin response and may predict suboptimal glycemic control as evidenced on daily glucose profiles of pregnant women with a single abnormally high OGTT value.