Neonatal Outcomes According to Different Glucose Threshold Values in Gestational Diabetes: A Register-based Study

Abstract

Abstract Background Mild hyperglycaemia is associated with increased birth weight but association with other neonatal outcomes is controversial. We aimed to study neonatal outcomes in untreated mild hyperglycaemia using different oral glucose tolerance test (OGTT) thresholds. Methods This register-based study included all (n = 4,939) singleton pregnant women participating a 75 g 2-hour OGTT in six delivery hospitals in Finland in 2009. Finnish diagnostic cut-offs for GDM were fasting ≥ 5.3, 1-hour ≥ 10.0 or 2-hour glucose ≥ 8.6 mmol/L. Women who did not meet these criteria but met the International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria (fasting 5.1–5.2 mmol/L and/or 2-hour glucose 8.5 mmol/L, n = 509) or the National Institute for Health and Clinical Excellence (NICE) criteria (2-hour glucose 7.8–8.5 mmol/L, n = 166) were considered as mild untreated hyperglycaemia. Women who met both the Finnish criteria and the IADPSG or the NICE criteria were considered as treated GDM groups (n = 1292 and n = 612, respectively). Untreated mild hyperglycemia groups and treated GDM groups were compared to controls, who were normoglycemic according to all criteria (fasting < 5.1 mmol/L, 1-hour glucose < 10.0 mmol/L and 2-hour glucose < 8.5 mmol/L, n = 3031). The primary outcome - a composite of adverse neonatal outcomes, including neonatal hypoglycaemia, hyperbilirubinaemia, birth trauma or perinatal mortality – was analysed using multivariate logistic regression. Results Compared to controls, the risk for the adverse neonatal outcome was not increased in mild hyperglycemia according to the IADPSG criteria (adjusted odds ratio [aOR]: 1.01, 95% confidence interval [CI]: 0.71–1.44) or the NICE criteria (aOR: 1.05, 95% CI: 0.60–1.85). Discussion The risk of adverse neonatal outcomes was not increased in mild untreated hyperglycaemia. The OGTT cut-offs of 5.3 mmol/L at fasting and 8.6 mmol/L at 2 hours seem to sufficiently identify clinically relevant GDM, without excluding neonates with a risk of adverse outcomes.