Fasting Glucose Testing in First Trimester Allows Early Risk Detection

Dr. Shlomit Riskin-Mashiah, from The Lady Davis Carmel Medical Center in Haifa noted that, "The findings highlight the potential benefits of using first trimester fasting glucose screening to detect women at a high risk of developing gestational diabetes mellitus."

"Screening in the third trimester provides only scant time to treat the condition," she added. "By contrast, diet and exercise interventions initiated in at-risk women during the second trimester might improve maternal and neonatal outcomes."

In the previously reported Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, at 24 to 32 weeks gestation, maternal blood glucose levels above normal but below those diagnostic of overt diabetes were associated with adverse pregnancy outcomes, including macrosomia, cesarean delivery and birth injury. In the current study, Dr. Riskin-Mashiah and colleagues evaluated links between first trimester fasting plasma glucose levels and adverse pregnancy outcomes.

Their retrospective analysis centered on 6,129 women with singleton pregnancies who had a first trimester fasting glucose level recorded. Women with pregestational diabetes, fasting glucose greater than 105 mg/dL, or delivery at less than 24 weeks were excluded.

As in the HAPO study, fasting glucose levels were analyzed in seven categories: less than 75, 75-79, 80-84, 85-89, 90-94, 95-99, and 100-105 mg/dL. At a median of 9.5 weeks gestation, the median fasting glucose level was 79 mg/dL.

According to the investigators, "With increasing fasting maternal glucose levels, the frequency of gestational diabetes mellitus development increased from 1.0% in the lowest category to 11.7% in the highest; the frequency of large for gestational age and/or macrosomia increased from 7.9% to 19.4%, and for primary cesarean section it increased from 12.7% to 20.0%."

For women in the highest category of first trimester fasting plasma glucose, the adjusted odds ratios for the development of gestational diabetes mellitus, large for gestational age and/or macrosomia, and primary cesarean section were 11.92, 2.82, and 1.94, respectively.

The risk of gestational diabetes mellitus "remained almost unchanged even after controlling for pregestational BMI, and the risk for large for gestational age and/or macrosomia was maintained even after excluding women with gestational diabetes mellitus," the investigators note in their report.

They also note that there was a "strong, graded association between first-trimester fasting glucose level and abnormal glucose challenge test and fair correlation between first-trimester fasting glucose level and fasting glucose level at the time of oral glucose tolerance test."

Whereas gestational diabetes mellitus screening is usually recommended at the start of the third trimester "in order to maximize the metabolic effects of pregnancy," the current study suggests that early screening may be worthwhile, the investigators note.

A large, prospective study looking at maternal and neonatal outcomes is needed to "better evaluate the association of first trimester fasting glucose levels and the usefulness of timely interventions on pregnancy outcome," the authors conclude.