In May I wrote about recommendations made by the International Association of Diabetes in Pregnancy Study Groups (IADPSG) for glucose tolerance testing in pregnancy. Those recommendations advocate for the use of a 75-gram oral glucose tolerance test to detect gestational diabetes mellitus (GDM) in pregnant women between 24 and 28 weeks gestation and were based on findings of the Hyperglycemia and Adverse Outcomes (HAPO) study. That study clearly demonstrated that the risks of adverse maternal and fetal outcomes continually increased as maternal glucose concentrations increased. The American Diabetes Association adopted the IAPDSG criteria and recommends that approach to identifying women with GDM.
In the September 2011 issue of Obstetrics and Gynecology, the American Congress of Obstetricians and Gynecologists (ACOG) opt to stick to their guns. The ACOG continues to recommend the "two-step" approach to screen and diagnose GDM. Step one is a screening test using either patient history, clinical risk factors, or with a 50 gram glucose administered orally followed by the measurement of blood glucose 1 hour later (a result greater than 140 mg/dL is considered abnormal). Those with an abnormal screening test go on to have the diagnostic test: a 100 gram oral glucose tolerance test with blood glucose measured over 3 hours.
The ACOG rightfully acknowledges that while the treatment of mild GDM decreases adverse infant outcomes there is no evidence to indicate that use of the IADPSG recommendations would result in any significant improvements in outcomes. Of course, lack of evidence doesn't mean that there is no benefit, it simply means that any benefits have not yet been demonstrated. The fact that widespread adoption of the IADPSG screening test would double the number of women diagnosed with GDM was also noted by the ACOG. This increase is notable because it would lead to a considerable increase in health care costs and likely overwhelm health care delivery systems.
In contrast to the ACOG, the National Academy of Clinical Biochemistry (NACB) have published guidelines that recommend the approach advocated by the IADPSG. Confused yet? Disagreement among professional groups is not unusual and consensus is not easy to come by. As usual, a lot more research is required before widespread agreement is achieved.