In a population of mothers with type 1 diabetes and their singleton infants, third-trimester glycemic measures were more predictive of bearing a large-for-gestational-age infant than were earlier parameters, and third-trimester episodic hyperglycemia was most predictive of all.
Dr. Lucrecia Herranz and colleagues at the University Hospital of La Paz in Madrid recruited from the hospital 73 mothers, who had given birth to 37 large-for-gestational-age (LGA) infants and 36 appropriate-for-gestational-age (AGA) infants. The investigators reported their findings in Diabetes Research and Clinical Practice (2007;75:42–6).
After researchers controlled for tobacco smoking and history of microsomia, mothers of LGA infants had significantly higher mean overall glucose levels in all trimesters than did mothers of AGA infants. But the difference was most pronounced in the third trimester, when LGA infants' mothers registered a mean glucose level of 7.4 mmol/L, vs. 6.9 mmol/L for mothers of AGA infants. Mean postprandial glucose in the third trimester was 8.4 mmol/L for mothers of LGA babies and 7.9 mmol/L for AGA neonates' mothers. Moreover, the portion of glucose values higher than the goal was 42% for LGA mothers and 35% for AGA mothers. HbA1c levels were significantly higher in the LGA group than in the AGA group only in the third trimester (6.2 vs. 5.9).
Logistic regression of all third-trimester glycemic measures showed that the percentage of third-trimester glucose values above the target value posed an increased likelihood of bearing an LGA infant (OR 1.09; 95% CI 1.02–1.15). AGA infants had a mean birth weight of 3,139 g, vs. 3,830 g for the LGA infants.
Notably, the two groups of mothers, all of whom had been managed at the hospital before conception, had no preconception differences in glycemic parameters.
Dr. Herranz and colleagues noted that their study supports the findings of prior studies that have posited an effect of intermittent maternal hyperglycemia on fetal growth. “Interestingly, our data show that of all third-trimester glycemic parameters, the percentage of glucose values above glycemic target is the most powerful predictor of LGA infants,” they wrote.