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.