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.