▸ GDM diagnosis made if at least two of these plasma glucose values are met or exceeded after the 100-g OGTT: fasting, 95 mg/dL; 1 hour, 180 mg/dL; 2 hour, 155 mg/dL; 3 hour, 140 mg/dL (if a 3-hour test is done).
One-Step Approach to GDM Dx:
▸ Screening of all women at 24–28 weeks' gestation not known to have type 2 diabetes with 75-g oral glucose tolerance test (after overnight fast).
▸ GDM diagnosis made if any one of these fasting plasma glucose values are met or exceeded: fasting, 92 mg/dL; 1 hour, 180 mg/dL; 2 hour, 153 mg/dL.
Sources: American Diabetes Association's Standards of Medical Care in Diabetes 2010 (Diabetes Care 2010;33:S11–61); American College of Obstetricians and Gynecologists Practice Bulletin, September 2001; ADA's Standards of Medical Care in Diabetes 2011 (Diabetes Care 2011;34:S11–61).
The Consequences of GDM
The thresholds for deciding when to begin treating hyperglycemia were established almost 50 years ago at a time when we had significantly less knowledge about the risk factors for and consequences of hyperglycemia in pregnancy. Because of this lack of understanding about the causes and consequences of hyperglycemia and our sometimes rigid adherence to these cutoffs, many women were not treated who should have been.
There is a growing recognition in the research and clinical communities that gestational diabetes mellitus (GDM) is a much more serious condition than had been previously believed even a decade ago. We now know that GDM, if not properly diagnosed and managed, can have intergenerational consequences in terms of propagating risks for obesity, diabetes, heart disease, and other disorders. Furthermore, there is a new and growing realization that even mild hyperglycemia significantly below what has traditionally been defined as diabetes can have significant adverse consequences for both mother and infant.
Perhaps the most significant complication of maternal hyperglycemia faced by ob.gyns. is the growing number of large-for-gestational-age (LGA) infants being born. For obvious reasons, LGA infants are more difficult to deliver and significantly more prone to experiencing shoulder dystocia and other injuries during normal or cesarean delivery, and cesarean delivery has its own set of complications for both baby and mother.
The large, multicenter Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study recently documented that by managing hyperglycemia – even among women who previously had not been considered to have any glucose control problems – the incidence of LGA-related problems and other adverse birth outcomes could be significantly reduced.
To discuss in detail the findings of the HAPO study and its potential clinical implications, we have invited Dr. Thomas R. Moore, professor and chairman of the department of reproductive medicine at the University of California, San Diego, to write this Master Class.
Dr. Moore's essay discusses both the unique design and findings of the HAPO study, and also explores the quandary faced by members of the International Association of Diabetes and Pregnancy Study Groups (IADPSG) in their attempts to translate HAPO's findings into clinically useful recommendations and guidelines.
In a sign of how complex and time consuming it can be to translate clinical research findings into clinical practice, the recommendations of the IADPSG are now being debated among research and medical societies, with some suggesting that the thresholds introduced by the HAPO study and advanced by the IADPSG are not significantly different from the current levels.
We greatly appreciate Dr. Moore's insights into these complicated but exciting developments. His Master Class installment will help all of us to better understand this complex issue so that we can potentially play a role in speeding up the process of changing the way we manage GDM.