Association between low blood glucose increase during glucose tolerance tests in pregnancy and impaired fetal growth.

OBJECTIVE: To evaluate how different levels of increase in maternal blood glucose from a fasting state to 2 h after an oral glucose challenge in late pregnancy are associated with fetal growth, with special emphasis on those with a low increase. DESIGN: Prospective cohort study. SUBJECTS: We followed 855 women, of whom 70% had an increased risk for carrying lighter babies. STUDY DESIGN AND METHODS: Ultrasound was used to estimate fetal growth in gestational weeks 25, 33 and 37. In week 37 the women had a 75-g oral glucose tolerance test, and fasting and 2-h capillary glucose values were recorded with the difference between these two called delta (∆) glucose. Three groups were constructed from the ∆ glucose distribution: Low below the 10th centile; Medium between the 10th and 90th centiles; and High above the 90th centile. Missing data were imputed. Linear and Poisson regression models were applied. OUTCOME MEASURES: Estimated fetal weight, percent deviation from expected fetal weight and anthropometric measures at birth. RESULTS: The Low group carried the lightest fetuses and the High group the heaviest. The fetal growth in the Low group deviated increasingly more in a negative direction from week 25 to 37 than in the other groups. CONCLUSION: In a high-risk population, a positive relation between ∆ glucose and fetal growth was found. The Low group demonstrated impaired growth. More attention should be paid to pregnant women with an insufficient increase in glucose after a glucose challenge. Future studies should challenge our findings in high-risk and low-risk populations.