One or two hours postprandial glucose measurements: Are they the same?

OBJECTIVE: This study was undertaken to compare the rate of abnormal glucos e levels measured after 1 hour (> 140 mg%) with those measured after 2 hour s (> 120 mg%) postprandially in women with gestational diabetes mellitus (G DM). STUDY DESIGN: Sixty-eight women were included in this study. All had GDM ba sed on the criteria of Carpenter-Coustan. Women with fasting glucose levels of 105 mg% or more were excluded from the study. All women were initially treated by diet. All women measured daily capillary blood glucose levels wh en fasting as well as 1 hour and 2 hours postprandially for 1 week, immedia tely after diagnosis of GDM. Glucose levels were obtained by memory-based g lucometers. All women were followed in a specialized gestational-diabetes c linic throughout the pregnancy. Insulin therapy was started on an individua l basis according to common clinical criteria. Epidemiologic and perinatal data were collected from medical charts. RESULTS: The average age of the women was 30.8 +/- 5.4 years. Thirty-five p ercent of participants were primipara. The mean gestational age at diagnosi s was 28.8 +/- 5.4 weeks. Glucose measurements included 618 readings during fasting and 2730 either I hour or 2 hours postprandial. Rates of abnormal glucose (> 95 mg% when fasting; > 140 mg% 1 hour or > 120 mg% 2 hours after each meal) per person were the following: fasting, 27.1% abnormal glucose measurements; postbreakfast, 22.4% abnormal levels after 1 and 8.5% after 2 hours (P < .01); postlunch, 16.4% abnormal levels after 1 hour and 18.2% a fter 2 hours (not significant); postdinner, 16.3% abnormal levels after 1 h our and 30.1% after 2 hours (P < .01). CONCLUSION: The rate of abnormal values was 2.5-fold greater 1 hour postbre akfast than 2 hours postbreakfast, in contrast to an opposite ratio of a 2- fold increase in the rate of abnormal values 2 hours postdinner versus 1 ho ur postdinner. Therefore, differential measurement (1 hour after breakfast and 2 hours after dinner) might impose stricter criteria for controlling bl ood glucose levels. Further clinical research should explore whether differ ential measurements might reduce the rate of diabetes-associated complicati ons.