50 gram oral glucose challenge test combined with risk factor-based screening for gestational diabetes

Abstract

Objective:

Our aim was to study whether universal screening of all pregnant women by Oral Glucose Challenge Test (OGCT) would identify a higher number of women with Gestational Diabetes (GDM) than risk factor based screening.

Study design:

A 50 g OGCT test was performed prospectively in 532 unselected women at 26–28 weeks of gestation. The 1-h venous plasma glucose concentration of >7.3 mmol/l was considered as a positive screening result. Patients with a positive OGCT underwent a 75 g 2-h OGTT, which was used as the actual diagnostic test for GDM. When two or all three of the glucose concentrations in OGTT (measured at fasting state and 1 and 2 h after the 75 g glucose load) were above the 97.5th percentile the patient was considered as having GDM. In addition, women with risk factors for GDM also underwent a 75 g OGTT regardless of the result of the OGCT.

Results:

A positive 50 g OGCT was obtained in 123 (23%) of the women. In 15 (12%) of these, a diagnosis of GDM was established by the subsequent OGTT. Out of the 409 remaining women with a normal OGCT, 148 (36%) had risk factors for GDM. An OGTT performed in these patients identified 4 additional women with a GDM. Seventy-nine percent of GDM was thus found with 50 g OGCT without regarding risk factors. Forty-seven percent of the women with GDM would have been missed in screening by risk factors only.

Conclusions:

In our population 50 g OGCT appears to identify a higher number of GDM than risk factor based screening. Combined with risk factor screening a few more cases of GDM would be found.

Introduction

There is evidence that even mild maternal hyperglycemia is a risk factor for fetal macrosomia, neonatal hypoglycemia and hyperbilirubinemia [1], [2], but these complications occur only in a minority of cases. The 2-h oral glucose tolerance test (OGTT) with only one abnormal value (defined as impaired glucose tolerance, IGT) has been shown to have minimal effects on perinatal outcome, at least when the patients adhere to an appropriate diet. An OGTT with two or three abnormal values, on the other hand, is associated with an increased risk for perinatal complications [3].

Failure to recognize gestational diabetes mellitus (GDM) may harm the fetus, whereas too aggressive screening results in many false-positive GDM diagnoses and subsequent unnecessary interventions.

The 50 g 1-h oral glucose challenge test (OGCT) remains the screening method of choice in North America. It is recommended by the American Diabetes Association (ADA) for women with risk factors [4]. In UK [5] and Northern Europe, the risk factor-based screening procedure followed by a 75 g OGTT as the diagnostic test is used. Universal screening with 50 g glucose load for all pregnant women has also been proposed [6], [7].

Our aim was to study whether universal screening of all pregnant women by OGCT would identify a higher number of GDM than risk factor based screening and how many more women with normal OGCT having risk factors would be diagnosed to have GDM.