Just over two-thirds of pregnant women undergo screening tests for gestational diabetes, according to a new analysis of nearly one million patient records.

Among the five percent of women who tested positive for pregnancy-related diabetes, just one in five were screened again within six months of giving birth, Dr. Jon M. Nakamoto of Quest Diagnostics Nichols Institute in San Juan Capistrano, California, and his colleagues found.

The findings are particularly concerning, Nakamoto told Reuters Health, given that a recent large study, the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) trial, found that even subtle defects in maternal glucose metabolism during pregnancy led to health problems for both mother and baby. Women who have gestational diabetes are also at increased risk of developing type 2 diabetes in the future, he added.

At present, the American College of Obstetricians and Gynecologists and the American Diabetes Association recommend screening pregnant women for gestational diabetes, and state that women who do develop pregnancy-related diabetes should be re-tested six to 12 weeks after delivering their babies.

The lab test now most commonly used for screening is the 100-gram oral glucose tolerance test. A woman drinks a heavily sweetened beverage, and then has her blood tested; if at least two tests reveal abnormally high glucose levels, she is considered to have gestational diabetes.

But the International Association of Diabetes and Pregnancy Study Groups now recommends, based on the HAPO study results, that a different test - the 75-gram oral glucose tolerance test - be used instead, with just a single abnormally high blood glucose result indicating pregnancy-related diabetes.

Based on these guidelines, Nakamoto noted, about twice as many women would be considered to have gestational diabetes compared to those diagnosed with the 100-gram test.

In their study, Nakamoto and his team looked at Quest Diagnostics testing data for pregnant women 25 to 40 years old (younger women are considered to be at low risk for gestational diabetes), including nearly 925,000 women in all.

According to their report in the journal Obstetrics and Gynecology, 68 percent (nearly 843,000) underwent oral glucose tolerance testing, and of these, five percent had gestational diabetes.

Women 35 to 40 years old were nearly twice as likely to have gestational diabetes as women 18 to 24, while risk for women weighing more than 275 pounds was more than triple that for women who weighed 100 to 124 pounds. Asian women were also at nearly double the risk of gestational diabetes compared to whites.

Among more than 23,000 patients who tested positive for gestational diabetes and continued to receive lab tests from Quest Diagnostics within six months of their due date, just 19 percent were tested for diabetes postpartum, the researchers found.

“Our nationally based study demonstrates that the pregnancy and postpartum screening rates of pregnant women are much less than the recommended guidelines from the American College of Obstetricians and Gynecologists and the American Diabetes Association,” Nakamoto and his team write. “It is also important to note that the proportion of women with (gestational diabetes mellitus) diagnosed returning for postpartum testing is extremely low.”

The US Preventive Services Task Force - the government body that issues recommendations on screening tests - currently states that existing data are not strong enough to recommend that all pregnant women receive screening for gestational diabetes.

But given the recent study, Nakamoto notes, that group will likely revisit their recommendation. “Now you have outcomes-based data from a very large international study that was conducted in the past couple of years. Those data I think really now add what the task force is looking for, outcomes-based data to show that it makes a difference.”

SOURCE: Obstetrics & Gynecology, online December 20, 2010