Screening for gestational diabetes mellitus: a critical review

Gestational diabetes mellitus (GDM) occurs in 1% to 3% of pregnant women. Generally, the clinical focus in these cases is on intermediate outcomes such as macrosomia, hypoglycemia, or hypocalcemia. Only macrosomia is consistently associated with gestational diabetes, yet the risks of macrosomia such as shoulder dystocia and birth injury are highly variable. The screening test and the reference standard, the oral glucose tolerance test, are problematic in that there are no standardized testing procedures or definitive criteria for diagnostic interpretation and poor reproducibility of test results. There have been no methodologically sound randomized controlled trials of therapy for GDM. Studies that attempted randomization show, however, that therapy reduces the incidence of macrosomia, which is an intermediate outcome. A critical review of the literature revealed that there is insufficient evidence to justify routine screening for gestational diabetes. A reassessment of the relation between maternal glucose levels in pregnancy and neonatal outcomes is needed to determine if there are correctable adverse outcomes. In the meantime, management should be based on careful assessment of each individual pregnancy.