Objective: To determine the normal response to a 75 g glucose challenge in the context of an oral glucose tolerance test in the third trimester of pregnancy.
Design: Prospective observational study.
Setting: Antenatal clinic, Kandang Kerbau Hospital, Singapore.
Subjects: Sixty-four normal pregnant women with a low risk for diabetes.
Interventions: Glucose (75 g) challenge following an overnight fast after 28 weeks of gestation.
Main outcome measure: Venous plasma glucose levels taken before and 2 h after the glucose challenge.
Results: Upper limits of normality were found to be fasting glucose 4.9 mmol/l and 2 h glucose 9.2 mmol/l.
Conclusion: The WHO (1980) criteria should not be used in pregnancy.
PIP: To assess the normal response to the 75 gm oral glucose tolerance test (OGTT) in normal pregnant women, healthy Chinese and Malay women who had been referred to the antenatal clinic of the Department of Reproductive Medicine, Kandang Kerbau Hospital, Singapore, were evaluated. The women were selected on the basis of having none of the generally accepted risk factors for diabetes mellitus: their age was 35 years, they weighed 80 kg, they did not have a personal history of diabetes or a family history of diabetes or a family history of diabetes in first degree relatives, nor did they have a history of babies weighing 4000 gm at birth, still-births, neonatal deaths, congenital malformations, or recurrent miscarriages. All OGTTs were performed after 28 weeks of gestation. The fasting blood sample was taken from the antecubital vein. Further samples were taken 1 and 2 hours after the glucose drink. A glucose analyzer using 5 mcl of plasma was employed. The analytical method was based on the glucose oxidase/peroxidase/aminophenazone process. There was no significant difference in mean glucose levels at corresponding points of the OGTT in Chinese and Malay women. correlation calculations confirmed the absence of any influence of gestational age after 28 weeks on glucose tolerance. Of the 64 women, 47 were Chinese and 17 Malays; 20 wee nulliparous, and 44 were parous. Their mean age was 27.2 years (range 18-35). The mean birthweight of the infants was 3140 gm (range 2094-4240 gm). There were 33 female and 31 male infants. The mean apgar scores at 1 and 5 min were 8.8 (range 7-9) and 9.0 (range 6-10). The mean values and the proposed upper limits of normality for the 75 gm OGTT were 3.9 and 4.9 mmol/1, respectively. 6 women had abnormal OGTT results according to the WHO criteria (fasting glucose 6 mmol/1; 2 hour glucose 8 mmol/1).