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NIH brings balance to recap of study on blood test for gestational diabetes

Blood test may identify gestational diabetes risk in first trimester

Our Review Summary

This release accurately describes an observational study using second-hand data from another study  which found that a relatively inexpensive blood test (HbA1c or A1C for short), commonly used to monitor diabetes, might help identify women at risk for getting gestational diabetes as early as the 10th week of pregnancy. The release does a good job of explaining that the disorder carries risks — including the development of adult type 2 diabetes long after birth — for both pregnant women and their newborns.

The release notes that the study does not scientifically demonstrate that measuring HbA1c levels in early pregnancy can in fact determine a woman’s later risk for gestational diabetes. On the down side, the release doesn’t mention what it would cost in dollars or potential over treatment to screen every women in the early weeks of pregnancy;  offers no information about the overall prevalence and incidence of gestational diabetes or any details about the women whose records were studied; and waits until the last sentence to note that there also is no firm evidence that lowering HbA1c levels with diet and exercise before or in early pregnancy will actually reduce risk for gestational diabetes.


Why This Matters

Public health and obstetrical associations estimate that 1 to 15% of all pregnant women in the U.S. develop gestational diabetes and no doubt a greater percentage worries they might. There are potentially serious health consequences to gestational diabetes for mother and child and although some mothers at higher than usual risk — for example, women with obesity — are screened early, most women have a screening blood glucose test later in pregnancy. Glucose and insulin levels are complicated to interpret later in pregnancy. The notion that earlier detection with a test that measures average  glucose levels over time might lead to lowered rates of the disorder is seductive.  But it’s also true that such a scenario is only speculation at this time. As a consequence, news releases about this topic are of fairly wide interest, but must be careful not to over promise.


Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

The absence of cost information is unfortunate in this release.  In general, the public has little experience of or understanding of the overall costs of routine, widespread screening. Sources put the cost of A1C screening at anywhere from $12 to $65. There are nearly 4 million live births in the U.S. each year, and many more pregnancies. Even if we use a $35 midpoint price, that’s $140 million just to screen for gestational diabetes. Worth it? Maybe. Particularly given that the glucose tolerance test given later in pregnancy has an average cost of $60 to $85, according to some sources. And the savings to be realized in potentially preventing gestational diabetes could be substantial. In any case, cost considerations are important in the overall scheme of health care delivery and limited health care dollars.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?


The release quantifies the results and potential benefits by noting that each 0.1 percent increase in HbA1c levels above 5.1 percent  in early pregnancy was associated with a 22 percent higher risk for gestational diabetes.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

The blood test itself is virtually harmless, and overall fairly reliable, but results can be skewed by a variety of unrelated diseases and lifestyle factors, resulting in false positives and negatives.

Does the news release seem to grasp the quality of the evidence?


The release notes the observational nature of the data and the relatively small number of women overall in the two groups analyzed and compared. Readers don’t learn much about the population of women studied — age, race, number of pregnancies, socioeconomic status, comorbidities, etc. But given that the release makes clear more research would be needed to prove the association identified in the study, we give this a “satisfactory” rating.

Does the news release commit disease-mongering?

Not Applicable

No mongering, but no data about frequency of the disorder, either.

Does the news release identify funding sources & disclose conflicts of interest?


Although not explicit, it seems clear the research was funded by NIH.

Does the news release compare the new approach with existing alternatives?


There currently is no standardized screening test for identifying gestational diabetes in the first trimester. Earlier research into the usefulness of HbA1c testing for gestational diabetes in early pregnancy have been limited to high risk groups.

Does the news release establish the availability of the treatment/test/product/procedure?


The release makes clear that this test is far from ready for use in clinical screening. It states:

The test is not currently recommended to diagnose gestational diabetes at any point in pregnancy.

Does the news release establish the true novelty of the approach?


The release is clear about the theoretical potential of the test to determine early risk, and eventually, the theoretical potential of lifestyle changes to modify that risk.

Total Score: 7 of 9 Satisfactory


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