PT  - JOURNAL ARTICLE
AU  - Christian Ouzilleau
AU  - Marie-Andrée Roy
AU  - Louiselle Leblanc
AU  - André Carpentier
AU  - Pierre Maheux
TI  - An observational study comparing 2-hour 75-g oral glucose tolerance with fasting plasma glucose in pregnant women: both poorly predictive of birth weight
DP  - 2003 Feb 18
TA  - Canadian Medical Association Journal
PG  - 403--409
VI  - 168
IP  - 4
4099  - http://www.cmaj.ca/content/168/4/403.short
4100  - http://www.cmaj.ca/content/168/4/403.full
SO  - CMAJ2003 Feb 18; 168
AB  - Background: The definition and treatment of glucose intolerance during pregnancy are matters of intense controversy. Our goal was to examine the value of the 75-g oral glucose tolerance test (OGTT) in terms of its ability to predict birth weight percentile in a group of women with singleton pregnancies who received minimal treatment for their glucose intolerance. Methods: We reviewed the results of OGTTs performed between 24 and 28 weeks' gestation in a group of 300 consecutive high-risk women (mean age 29.5 years [95% confidence interval, CI, 28.9–30.1]; parity 1.5 [95% CI 1.4–1.7]) whose plasma glucose level 1 hour after a randomly administered 50-g glucose load was 8.0 mmol/L or above. These data were compared with results for a randomly selected control group of 300 women whose plasma glucose level 1 hour after a 50-g glucose load was less than 8.0 mmol/L (mean age 28.0 years [95% CI 27.4–28.6]; parity 1.5 [95% CI 1.3–1.6]). Results: For 76 (25.3%) of the 300 high-risk women, the plasma glucose level 2 hours after a 75-g glucose load (confirmatory OGTT) was 7.8 mmol/L or more, but only 6 of these were treated with insulin, which emphasizes the low level of intervention in this group. Thirty (10.0%) of the neonates in this group were large for gestational age (LGA; adjusted weight at or above the 90th percentile). This proportion did not significantly differ from the proportion for the control group (25 or 8.3%). After exclusion of the 6 insulin-treated women, simple correlations between birth weight percentile and fasting or 2-hour plasma glucose levels were very weak (r = 0.23 and 0.16 respectively; p < 0.01). The correlation between birth weight percentile and fasting or 2-hour plasma glucose persisted in a multiple regression analysis that included the following maternal variables: age, prepregnancy weight, weight gain during pregnancy, parity and smoking. In the multivariate models, the standardized coefficients for fasting and 2-hour plasma glucose levels were low (r = 0.19 [p < 0.001] and r = 0.13 [p = 0.02] respectively). These multivariate models could not explain more than 22% of the total variability in birth weight percentile. Interpretation: In this population of pregnant, untreated diabetic women, plasma glucose levels (either fasting or after various glucose loads) were independently but poorly correlated with birth weight; no more than 3% to 5% of birth weight variability could be explained by changes in glucose tolerance. Fasting plasma glucose was consistently but marginally better than the plasma glucose level 2 hours after 75-g glucose load for predicting LGA neonates. We conclude that neonatal macrosomia is influenced by variables that are largely independent of plasma glucose concentrations.