Self-Monitored Blood Glucose in Pregnant Women Without Gestational Diabetes Mellitus

The Fourth Workshop-Conference on Gestational Diabetes Mellitus (GDM) recommended to lower maternal blood glucose (BG) goals (1). However, data on glucose values in nondiabetic pregnant women are scant and targets have not been derived from clinical trials (1). In addition, the regression line between laboratory and capillary BG measurements deviates from the origin with differences between meters (2).

We aimed to assess the BG range in pregnant women without GDM using self-monitoring of blood glucose (SMBG) with three reflectance meters (Accutrend Sensor, One Touch, and Precision). Universal GDM screening was performed using criteria from the first Workshop-Conference at three periods during pregnancy (before 24 weeks, at 24–28 weeks, and at 32–35 weeks). A total of 36 pregnant women were studied shortly after a normal screening/oral glucose tolerance test (12 subjects per period). Within each period, permuted-block randomization was performed and then separated into six groups (2 reflectance meters, sequence of use). Women were asked to perform SMBG before and 1 h after each main meal while maintaining their usual diet and activity. At each time two BG measurements were performed, one with each meter.

Maternal age was 30.2 years (24–38), BMI was 24.1 kg/m² (18.6–33.0), the gestational age at second screening was 26.0 weeks (24–29), and plasma glucose 1 h after challenge was 112.0 mg/dl (77–174), without differences between groups (Kruskall-Wallis ANOVA). Women who were tested after the first period performed monitoring at a gestational age of 16 weeks (12–23), those who were tested after the second period performed monitoring at 27.5 weeks (24–30), and those who were tested after the third period performed monitoring at 36 weeks (32–39). Differences for capillary BG (mg/dl) in the three periods were tested with ANOVA and adjusted for the meter. Fasting BG decreased (first period 88.0 ± 9.4, second period 87.5 ± 14.0, and third period 78.8 ± 15.8) and 1-h postprandial BG increased in the third period (105.9 ± 21.6, 109.5 ± 15.5, and 117.5 ± 21.4), whereas no change was observed for preprandrial (lunch/dinner) BG (85.9 ± 14.1, 87.7 ± 15.2, and 80.9 ± 17.7) and no influence for the meter was observed.

After we translated these results into practice, the first conclusion is that different meters do not seem to be a main determinant of SMBG values. Knowledge of SMBG values in healthy pregnant women can be used to establish glycemic goals for diabetic pregnant women. Recently, the maximal value for mean 1-h postprandial BG in healthy pregnant women (105.2 mg/dl) has been proposed as the target for diabetic pregnant women (3,4). This can be considered too tight because half of the pregnant population would be over the target, and to decrease BG implies risk (5). A range between mean and +1 SD or +1 SD and +2 SD would be safer. In this study, mean to +2 SD would translate into fasting BG 88–111 mg/dl before 30 pregnancy weeks and 79–110 mg/dl afterward, preprandrial BG (lunch/dinner) 85–116 mg/dl throughout pregnancy, and 1-h postprandial BG 108–145 mg/dl before 30 weeks and 118–160 mg/dl afterward. In the aforementioned study (3), mean +2 SD for 1-h postprandial BG is <115 mg/dl, a figure remarkably lower. We have no clear explanation for the difference; it cannot be attributed to obesity (data not shown), and we can only speculate on the influence of reagent storage and meter calibration. This underscores the importance of additional information on SMBG values in healthy pregnant women.