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

This study was undertaken to compare the rate of abnormal glucose levels measured after 1 hour (>140 mg%) with those measured after 2 hours (>120 mg%) postprandially in women with gestational diabetes mellitus (GDM).Sixty-eight women were included in this study. All had GDM based 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 when fasting as well as 1 hour and 2 hours postprandially for 1 week, immediately after diagnosis of GDM. Glucose levels were obtained by memory-based glucometers. All women were followed in a specialized gestational-diabetes clinic throughout the pregnancy. Insulin therapy was started on an individual basis according to common clinical criteria. Epidemiologic and perinatal data were collected from medical charts.The average age of the women was 30.8 +/- 5.4 years. Thirty-five percent of participants were primipara. The mean gestational age at diagnosis was 28.8 +/- 5.4 weeks. Glucose measurements included 618 readings during fasting and 2730 either 1 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% after 2 hours (not significant); postdinner, 16.3% abnormal levels after 1 hour and 30.1% after 2 hours (P < .01).The rate of abnormal values was 2.5-fold greater 1 hour postbreakfast 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 hour postdinner. Therefore, differential measurement (1 hour after breakfast and 2 hours after dinner) might impose stricter criteria for controlling blood glucose levels. Further clinical research should explore whether differential measurements might reduce the rate of diabetes-associated complications.