Maternal glucose levels that were high but below the diagnostic threshold for gestational diabetes were strongly associated with high fetal insulin levels and birth weights in a large international study.
There were also weaker—but still significant—associations between maternal hyperglycemia that fell short of overt gestational diabetes, as well as a host of neonatal problems that included hypoglycemia in the neonate, the need for cesarean delivery, premature delivery, shoulder dystocia or birth injury, the need for intensive neonatal care, hyperbilirubinemia, and preeclampsia.
These findings “indicate the need to reconsider current criteria for diagnosing and treating hyperglycemia during pregnancy,” said Dr. Boyd E. Metzger of Northwestern University, Chicago, and his associates in the Hyperglycemia and Adverse Pregnancy Outcome study.
The investigators assessed 23,316 pregnant women in an effort “to clarify the risk of adverse outcomes associated with degrees of maternal glucose intolerance less severe than overt diabetes mellitus.”
The study subjects underwent standard oral glucose tolerance testing at 24–32 weeks' gestation at 15 medical centers in nine countries.
Cord blood specimens were obtained at delivery to assess serum C-peptide levels, an indicator of fetal β-cell function.
High levels of fasting, 1-hour, and 2-hour plasma glucose were strongly correlated with birth weight above the 90th percentile and C-peptide levels above the 90th percentile, and the rates of these problems were found to increase as the plasma glucose levels increased, the investigators reported (N. Engl. J. Med. 2008;358:1991–2002).
There were weaker but significant correlations between maternal hyperglycemia and two other primary outcomes of this study (the need for cesarean delivery and clinical neonatal hyperglycemia), as well as five secondary outcomes.
A similar dose-response relationship was seen between increasing maternal glucose level and rising rates of these problems, Dr. Metzger and his associates said.