Gestational Diabetes Mellitus and Pregnancy Outcomes

Summary

A systematic review 1 included 8 cohort studies with a total of 44 829 women. Gestational diabetes (GDM) was diagnosed by 2 h 75 g oral glucose tolerance test (OGTT). Only studies that applied the OGTT universally to all participants (with or without risk factors) were included. Diagnostic criteria by WHO (fasting≥7 mmol/l [≥126 mg/dl] or 2 h plasma glucose≥7.8 mmol/l [140 mg/dl]) and by the International Association of the Diabetes in Pregnancy Study Group (IADPSG) (fasting glucose≥ 5.1 mmol/L [92 mg/dl], or 1 hour result of ≥ 10.0 mmol/L [180mg/dl], or 2 hour result of ≥ 8.5 mmol/L [153 mg/dl]) were used.Greater risk of adverse outcomes was observed for both diagnostic criteria. When using the WHO criteria, consistent associations were seen for macrosomia (birth weight over 4000g: RR 1.81, 95%CI 1.47 to 2.22; 5 trials, I²=0%); large for gestational age (defined as birthweight ≥90th percentile for gestational age: RR 1.53, 95%CI 1.39 to1.69; 4 trials; I² = 0%); pre-eclampsia (RR 1.69, 95%CI 1.31 to 2.18; 4 trials); and caesarean delivery (RR 1.37, 95%CI 1.24 to1.51; 4 trials). There was a trend towards increased perinatal mortality (RR 1.55, 95% CI 0.88 to 2.73) Less data were available for the IADPSG criteria, and associations were inconsistent across studies (I² > 73%). Magnitudes of RRs and their 95% CIs were 1.73 (1.28 to 2.35) for large for gestational age; 1.71 (1.38 to 2.13) for pre-eclampsia; and 1.23 (1.01 to1.51) for caesarean delivery. Excluding either the HAPO or the EBDG studies minimally altered these associations.

A retrospective observational cohort study 2 in Australia included 4 081 pregnant women with positive 50 g glucose challenge test but without pre-gestational diabetes. Participants were grouped into 4 cohorts: no GDM (control); GDM on Australasian Diabetes in Pregnancy (ADIPS) 1998 criteria only (treated); GDM on IADPSG 2010 criteria only (untreated); and GDM on both criteria (treated). The association of each cohort with pregnancy outcome measures, including birthweight centile, delivery gestation, primary caesarean section, shoulder dystocia and stillbirth, together with the effect of obesity, were examined.Women diagnosed with GDM according to the IADPSG 2010 (untreated) but not the ADIPS 1998 criteria (treated) had an increased risk of being large for gestational age (LGA) (OR 2.45, 95% CI 1.46 to 4.12, P = 0.001) and primary caesarean section (OR 2.03, 95% CI 1.23 to 3.35, P = 0.006) compared to control women. Among the women in this untreated group and women without GDM, obese women had an increased risk of LGA (OR 3.82, 95% CI 2.87 to 5.10, P < 0.001), shoulder dystocia (OR 1.50, 95% CI 1.03 to 2.19, P = 0.04) and primary caesarean section (OR 1.63, 95% CI 1.26 to 2.10, P < 0.001), compared to those women of normal weight.

An RCT 3 compared the prevalence of GDM and incidence of adverse maternal and neonatal outcomes in women diagnosed with GDM using the WHO criteria and the IADPSG criteria in Malaysia. 520 patients were randomized into the WHO and the IADPSG groups. All eligible women underwent a standard 75g OGTT (fasting and 2 h post prandial glucose levels). The prevalence of GDM in both groups were similar (37.9% vs. 38.6%). GDM women in the WHO group had a significantly higher incidence of gestational hypertension or preeclampsia (p = 0.004) and neonatal hypoglycemia (p = 0.042). In contrast, GDM women in the IADPSG group had a significantly higher incidence of fetal macrosomia (p = 0.027) and cesarean section (p = 0.012).