The 75-Gram Glucose Load in Pregnancy

• Published in: Diabetes care Vol. 26; no. 4; pp. 1206 - 1210
• Main Authors: Mello, Giorgio, Parretti, Elena, Cioni, Riccardo, Lucchetti, Roberto, Carignani, Lucia, Martini, Elisabetta, Mecacci, Federico, Lagazio, Corrado, Pratesi, Monica
• Format: Journal Article
• Language: English
• Published: American Diabetes Association 01-04-2003
• ISSN: 0149-5992; 1935-5548
• DOI: 10.2337/diacare.26.4.1206

The 75-Gram Glucose Load in Pregnancy
Relation between glucose levels and anthropometric characteristics of infants born to women with normal glucose metabolism
Giorgio Mello , MD 1 ,
Elena Parretti , MD 1 ,
Riccardo Cioni , MD, MSC 1 ,
Roberto Lucchetti , MD 1 ,
Lucia Carignani , MD 1 ,
Elisabetta Martini , MD 1 ,
Federico Mecacci , MD 1 ,
Corrado Lagazio , PHD 2 and
Monica Pratesi , PHD 3
1 Department of Gynecology, Perinatology and Human Reproduction, University of Florence, Florence, Italy
2 Department of Statistic Sciences, University of Udine, Udine, Italy
3 Department of Mathematics, Statistics, Informatics and Applications, University of Bergamo, Bergamo, Italy
Abstract
OBJECTIVE —To investigate, in pregnant women without gestational diabetes mellitus (GDM), the relation among obstetric/demographic characteristics;
fasting, 1-h, and 2-h plasma glucose values resulting from a 75-g glucose load; and the risk of abnormal neonatal anthropometric
features and then to verify the presence of a threshold glucose value for a 75-g glucose load above which there is an increased
risk for abnormal neonatal anthropometric characteristics.
RESEARCH DESIGN AND METHODS —The study group consisted of 829 Caucasian pregnant women with singleton pregnancy who had no history of pregestational diabetes
or GDM, who were tested for GDM with a 75-g, 2-h glucose load, used as a glucose challenge test, in two periods of pregnancy
(early, 16–20 weeks; late, 26–30 weeks), and who did not meet the criteria for a GDM diagnosis. In the newborns, the following
abnormal anthropometric characteristics were considered as outcome measures: cranial/thoracic circumference (CC/TC) ratio
≤10th percentile for gestational age (GA), ponderal index (birth weight/length 3 × 100) ≥90th percentile for GA, and macrosomia (birth weight ≥90th percentile for GA), on the basis of growth standard development
for our population. For the first part of the objective, logistic regression models were used to identify 75-g glucose load
values as well as obstetric and demographic variables as markers for abnormal neonatal anthropometric characteristics. For
the second part, the receiver operating characteristic (ROC) curve was performed for the 75-g glucose load values to determine
the plasma glucose threshold value that yielded the highest combined sensitivity and specificity for the prediction of abnormal
neonatal anthropometric characteristics.
RESULTS —In both early and late periods, maternal age >35 years was a predictor of neonatal CC/TC ratio ≤10th percentile and macrosomia,
with fasting 75-g glucose load values being independent predictors of neonatal CC/TC ratio ≤10th percentile. In both periods,
1-h values gave a strong association with all abnormal neonatal anthropometric characteristics chosen as outcome measures,
with maternal age >35 years being an independent predictor for macrosomia. The 2-h, 75-g glucose load values were significantly
associated in both periods with neonatal CC/TC ratio ≤10th percentile and ponderal index ≥90th percentile, whereas maternal
age >35 years was an independent predictor of both neonatal CC/TC ratio ≤10th percentile and macrosomia. In the ROC curves
for the prediction of neonatal CC/TC ratio ≤10th percentile for GA in both early and late periods of pregnancy, inflection
points were identified for a 1-h, 75-g glucose load threshold value of 150 mg/dl in the early period and 160 mg/dl in the
late period.
CONCLUSIONS —This study documented a significant association, seen even in the early period of pregnancy, between 1-h, 75-g glucose load
values and abnormal neonatal anthropometric features, and provided evidence of a threshold relation between 75-g glucose load
results and clinical outcome. Our results would therefore suggest the possibility of using a 75-g, 1-h oral glucose load as
a single test for the diagnosis of GDM, adopting a threshold value of 150 mg/dl at 16–20 weeks and 160 mg/dl at 26–30 weeks.
CC/TC ratio, cranial/thoracic circumference
GA, gestational age
GCT, glucose challenge test
GDM, gestational diabetes
GTT, glucose tolerance test
OR, odds ratio
ROC, receiver operating characteristic
Footnotes
Address correspondence and reprint requests to Dr. Giorgio Mello, Via Masaccio, 92, 50100 Florence, Italy. E-mail: mellog{at}unifi.it .
Received for publication 29 May 2002 and accepted in revised form 2 January 2003.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
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