The 75-g glucose tolerance test in pregnancy: a reference range determined on a low-risk population and related to selected pregnancy outcomes.
OBJECTIVE
To determine a reference range for the 75-g glucose tolerance test (GTT) in pregnancy using a group of women at low risk for gestational diabetes mellitus (GDM) and to determine the validity of this reference range by examining selected pregnancy outcomes for glucose-tolerant women with a 2-h result on the GTT up to 1.0 mmol/l below the diagnostic level for GDM compared with treated women with GDM.


METHODS
The reference range for the GTT was determined in 573 Caucasian women with an age <25 years and a BMI of <25 kg/m2. Selected pregnancy outcomes were compared between 272 treated women with GDM (diagnosed on the basis of a 2-h glucose level > or =8.0 mmol/l) and 308 women with a 2-h glucose level of 7.0-7.9 mmol/l.


RESULTS
There was 95% confidence that at least 95% of all the fasting glucose levels are < or =5.1 mmol/l(92 mg/dl) and 95% confidence that at least 95% of all the 2-h glucose levels were < or =7.8 mmol/l (140 mg/dl). Treated women with GDM had a significantly reduced rate of large-for-gestational-age infants compared with glucose-tolerant women, without any increase in the rate of small-for-gestational-age infants or obstetric interventions.


CONCLUSIONS
The reference range for the GTT in pregnancy should be determined on a low-risk population rather than on a total population. Consideration should be given to lowering the fasting glucose level to 5.0 mmol/l (90 mg/dl) and the 2-h level to 7.8 mmol/ (140 mg/dl). Glucose-tolerant women below this relatively low reference range have an increased rate of large-for-gestational-age infants and may benefit from treatment.
Moses
R G
RG
Illawarra Area Health Service, Wollongong, New South Wales, Australia. robertvmoses@uow.edu.au
Moses
M
M
Russell
K G
KG
Schier
G M
GM
D000328:Adult; D001315:Australia / Q000453:epidemiology; D015992:Body Mass Index; D016640:Diabetes, Gestational / Q000453:epidemiology; D005260:Female; D005951:Glucose Tolerance Test / Q000592:standards*; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D012016:Reference Values