Universal Screening for GDM at 24 Weeks

Universal Screening for GDM at 24 Weeks

According to DiabetesinControl.com web site, there is a new recommendation for universal screening of Gestational Diabetes Mellitus (GDM)between 24 and 27 weeks of pregrancy ("Task Force Recommends Universal Screening for GDM at 24 Weeks," 2014). The recommendation comes from the U.S. Preventive Services Task Force (USPSTF) ("Screening for Gestational Diabetes Mellitus," 2014).

Universal screening has been a subject of discussion for years. One can point to dozens of studies over the years which showed little benefit from universal screening. One I pulled is a study out of Australia which concluded there was minimal benefit for doing universal screening (Davey & Hamblin, 2001). This is just one of many studies which came to the same conclusion. Specifically the finding is stated as follows: “6,032 women who gave birth at the hospital, May 1996 to August 1997 and November 1997 to August 1998; all were screened for GDM, and 313 were diagnosed with the condition” (Davey & Hamblin, 2001). The basic thought at that time was look we took 6,032 women and screened them all they found 313 (or slightly over 5%) cases of GDM were found. The authors feeling is that a 5% detection rate is not worth the cost, inconvenience and scaring of women who are subjected to the test.

As I said this is one study there are many others. However, over the years the evidence started to change. This is the statement offered which justifies this change “In 2008, the USPSTF concluded that there was insufficient evidence to assess the balance of benefits and harms of screening for GDM either before or after 24 weeks of gestation. To update the 2008 recommendation, the USPSTF commissioned a systematic review of the evidence on the accuracy of screening tests, the benefits and harms of screening before and after 24 weeks of gestation, and the benefits and harms of treatment for the mother and infant. Pregestational diabetes (undiagnosed type 2 diabetes mellitus) is not the focus of this recommendation” ("Screening for Gestational Diabetes Mellitus," 2014).

This is a big change and when followed it does have same consequences for women as was first used to reject universal screening. The initial test that is being used is the “50-g OGCT is performed between 24 and 28 weeks of gestation in a nonfasting state” ("Screening for Gestational Diabetes Mellitus," 2014). Obviously there are some issues.

The first issue is cost. More testing means more costs, and insurance will be reluctant to support the change at least at first. Cost for the test will vary in different markets, but universal screening will result in a cost increase for each pregnancy in the US.

Second of course is how much it will scare the heck out of women. I do not know how many of you have ever done one of these things but it is not a fun test. In case you would like to read about it here is a nice blog about one woman’s experience with the test in Australia: http://www.mommylace.com/2010/03/14/ogct-oral-glucose-challenge-test/ .

Finally, there is a cost of false positives. A certain number of women will test positive for GDM and will not actually have the condition. When GDM is positive a second fasting blood sugar test is conducted. The second test is termed the GTT. The GTT is conducted using a 75g or 100g solution with testing (blood draws) at two three and four hours.

This recommendation is a 180 degree change from prior practice. Some doctors will follow it, others not. But unless it is changed it will, over time, be a near universal practice. You cannot blame the doctors for adopting these more conservative practices. Given the present state of litigation a doctor might be defenseless if the GDM is not recommended.

I used to have to do the GTT test every year. I did it every year for 14 years and in fact I did it just 3 months before I was diagnosed as being type 1. At that time passing this test was most successful test result, I was having, heck of I could do that well in German I might knwo more than 'Guten Morgen'. With the GTT I passed every year, with German, not so much. I hated taking the GTT so maybe I am just really sensitive to how awful it is, when a woman is told to do one of these tests.

At the same time I was an extra-large baby, the product no doubt of Gestational Diabetes so I really get it. Hey times were different in 1957. Had mom been treated I may not have been a 12 pound baby and the vaginal delivery would have been less of a trial. One can understand why mom was told to never have another child. Again it was 1957. Saying she could not have another child, broke my mom’s heart. She so wanted more children and finding out shortly after my birth that it was not permitted was just not the news she was hoping for. Maybe in in 1957 when women were sometimes judged by the number of children they had mom saw her worth diminished by the news? I hope not. I know as a child I was certainly very different than my friends and that was an issue until I got to High School.

I am passionate about doing the right thing to help women being treated for gestational diabetes. I hope the new guidelines improve pregnancy outcomes. The USPSTF estimates that the incidence of GDM in the population ranges from 7% to 12%. That like the new guidelines is a lot.


Davey, R. X., & Hamblin, P. S. (2001). Selective versus universal screening for gestational diabetes mellitus: an evaluation of predictive risk factors. The Medical journal of Australia, 174(3), 118-121.

Screening for Gestational Diabetes Mellitus. (2014). Retrieved January 22, 2014, from http://www.uspreventiveservicestaskforce.org/uspstf13/gdm/gdmfinalrs.htm

Task Force Recommends Universal Screening for GDM at 24 Weeks. (2014). Retrieved January 21, 2014, from http://www.diabetesincontrol.com/index.php?option=com_content&view=article&id=15745&catid=1&Itemid=17



I've always found it interesting that GD is diagnosed with an OGTT and all it takes to be diagnosed with GD is Impaired Glucose Tolerance (IGT). You could have great fasting numbers and a normal HbA1c and still get diagnosed with GD. I think it is imperative that women get diagnosed with GD as early as possible so that they can avoid problems. What I can't understand is why we don't apply the same logic to T2. Millions of people would be diagnosed earlier with IGT as a criteria. The IDF uses it as a criteria, but not in the US. It is like we just don't want to know.