Comment: The quality of evidence is upgraded by consistent results.
A systematic review 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.
Date of latest search: 31 March 2012