International Association of Diabetes and Pregnancy Study Group he IADPSG sponsored a workshop conference on the diagnosis and classiication of gestational diabetes in 2008. After reviewing the results of the HAPO study, a panel developed recommendations for the diagnosis and classiication of hyperglycemia during pregnancy. This panel allowed for the diagnosis of overt diabetes during pregnancy as shown in Table 57-4. It also recommended a single-step approach to the diagnosis of gestational diabetes using the 75-g, 2-hour OGTT. hresholds for fasting, 1-, and 2-hour values based on mean glucose concentrations from the entire HAPO study cohort were considered. hese glucose level thresholds were derived using an arbitrary 1.75 odds ratio of outcomes such as LGA birthweight and cord serum C-peptide levels >90th percentile. Only one of these thresholds, shown in Table 57-11, would need to be met or exceeded to make the diagnosis of gestational diabetes.
It is estimated that implementation of these recommendations would raise the prevalence of gestational diabetes in the United States to 17.8 percent! Said another way, the number of women with mild gestational diabetes would grow almost threefold with no evidence of treatment benefit (Cundy, 2012). Feldman and coworkers (2016) evaluated the implementation of the IADPSG paradigm in a before-ater analysis that included more than 6000 women. he new strategy was associated with a significant increase in gestational diabetes by the Agency for Healthcare Research and Quality Evidence-Based Practice Center, expert testimony, and a nonbiased panel to produce the overall report. he panel concluded that there were potential beneits to worldwide standardization. However, it found insuicient evidence to adopt a one-step diagnostic process such as the one proposed by the IADPSG. Moreover, as mentioned previously, after consideration of these indings, the American College of Obstetricians and Gynecologists (2017a) continues to recommend a two-step screening and diagnostic approach to gestational diabetes diagnosis. he College noted no significant improvements in maternal or perinatal outcomes that would ofset the tripling of gestational diabetes incidence that would derive from the one-step approach. We applaud this decision.
Adverse consequences of gestational diabetes difer from those of pregestational diabetes. Unlike in women with overt diabetes, women with gestational diabetes do not appear to have fetuses with substantially higher rates of anomalies than the general obstetrical population (Sheield, 2002). In a study of more than 1 million women from the Swedish Medical Birth Registry, major malformation rates were marginally elevated in fetuses of gestational diabetics compared with those of nondiabetic controls-2.3 versus 1.8 percent (Fadl, 2010). The stillbirth rate was not greater in this study. Similarly, the stillbirth rate was not increased in an analysis by Jovanovic and associates (2015) of more than 800,000 pregnancies from 2005 through 2011. In contrast, and not unexpectedly, women with elevatedfasting glucose levels have elevated rates of unexplained stillbirths similar to those of women with overt diabetes. This increasing risk with progressive maternal hyperglycemia emphasizes the importance of identiying women with evidence of preexisting diabetes early in pregnancy (see Table 57-4). Similar to women with overt diabetes, adverse maternal efects associated with gestational diabetes include a higher frequency of hypertension and cesarean delivery.