May 7, 2008 -- Babies born to women with even slightly higher-than-normal
blood sugar levels are at increased risk for a range of pregnancy and delivery-related
complications, findings from an international study confirm.
The large study examined the risks associated with having elevated blood
sugar during pregnancy that is not high enough to be considered gestational diabetes.
More than 25,000 pregnant women from nine countries took part in the
Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, which appears in the
May 8 issue of The New England Journal of Medicine and was largely
funded by the National Institutes of Health.
Even a small rise in blood sugar above what is considered normal was
associated with an increase in adverse outcomes, including high birth weight,
C-section delivery, and preeclampsia, a complication that can lead to premature
birth and can be deadly if not treated.
The findings make it clear that elevated blood sugar has a direct negative
impact on pregnancy and delivery, study co-author Donald R. Coustan, MD, tells
Coustan is professor and chairman of obstetrics and gynecology at Brown
University Medical School.
"This lays to rest many of the criticisms about gestational diabetes
treatment," Coustan says. "The critics have said that it isn't
elevated glucose that leads to negative outcomes, it is obesity or maternal age or some
other risk factor. But we were able to control for these risk factors, and
glucose was still a major determinant of outcomes."
Who Should Be Treated?
One important question that remains unanswered is whether the threshold for
treating high blood sugar in pregnancy should be lowered and if so, by how
"Because there was a continuous relationship that was even seen in women
with glucose levels considered near normal, this study isn't very helpful for
trying to pinpoint where the cutoff should be," Coustan says.
In an editorial accompanying the study, diabetes researchers Jeffrey Ecker,
MD, and Michael Greene, MD, of Harvard Medical School, conclude that the
current evidence does not support lowering the threshold for gestational
diabetes diagnosis and treatment.
While women in the HAPO trial with higher blood sugar levels also had higher
rates of delivering high birth-weight babies, they also gave birth to fewer
babies who were small for their gestational age.
And while C-section rates increased with increasing blood sugar in the HAPO
study, the increase was modest. Treatment to lower blood sugar levels was found
to have no impact on C-section deliveries in a similar study of pregnant women
with high-normal blood sugar.
"Until trials show clinical benefits for expanding the diagnostic
criteria for 'gestational diabetes,' we would not favor any change," Ecker
and Greene write.
Next month, an internationally representative group of diabetes, pregnancy,
and public health experts will meet in Pasadena, Calif., to make their own
"Right now, there is a total lack of agreement about what should be
called gestational diabetes and who should be treated," HAPO project
manager Lynn P. Lowe, PhD, of Northwestern University tells WebMD.