Isolated abnormal value during the 3-hour glucose tolerance test: which value is associated with macrosomia?

Objective: The aim of this retrospective review was to evaluate obstetric outcomes in patients with an isolated abnormal value on the oral glucose tolerance test (OGTT) at 0, 1, 2, and 3 h.

Methods: From January 2003 through June 2009, all consecutive pregnant women who presented to Baskent University were screened for gestational diabetes mellitus (GDM). Patients with one abnormal value based on findings of the OGTT were grouped according to increased levels of glucose at 0, 1, 2, and 3 h (Group 1  >  95 mg/dl for fasting glucose concentration, Group 2  >  180 mg/dl for the serum glucose concentration in the first hour, Group 3  >  155 mg/dl for the serum glucose concentration in the second hour, Group 4  >  140 mg/dl for serum glucose concentration in the third hour). The four groups were compared for classic GDM risk factors. The primary outcome measures were large for gestational age (LGA) (birthweight  > 95th percentile for gestational age using population birth weight centile charts) and macrosomia.

Results: The incidence of LGA baby (Group 1, 10%; Group 2, 3.8%; Group 3 20.3%; Group 4, 13.2%; p = 0.008) was significantly highest in Group 3 and macrosomia (Group 1, 30%; Group 2, 5.1%; Group 3, 18.6%; Group 4, 15.8%; p = 0.039) was significantly higher in Groups 1 and 3.

Conclusions: Our results suggest that even with relatively mild degrees of glucose intolerance at 2 h, no treatment is associated with LGA babies.