Adverse pregnancy outcome in women with mild glucose intolerance: is there a clinically meaningful threshold value for glucose?

Background. The diagnostic criteria of gestational diabetes mellitus (GDM) have been based on the risk of future maternal diabetes rather than the short‐term risk of mother and infant. Our aim was to illustrate the relation between various adverse pregnancy outcomes and maternal glucose levels in women with mild glucose intolerance using a graphical approach. Methods. Observational study of 2,885 pregnant women examined with a 2‐h, 75‐g oral glucose tolerance test (OGTT) based on risk indicators. Only women with 2‐h capillary blood glucose <9.0 mmol/l were included, as women with 2‐h values ≥9.0 mmol/l were treated for GDM. Empirical frequencies of adverse outcomes were related to 2‐h values by linear and quadratic logistic models. Adjustments for well‐known confounders were performed by a multiple logistic model. Results. Linear trends were demonstrated for the outcomes: shoulder dystocia, caesarean section rate (univariate analysis only), spontaneous preterm delivery, and macrosomia (large‐for‐gestational age infants). None of the outcomes deviated significantly from linearity. No significant trend was found for hypertension or neonatal hypoglycaemia and jaundice. Conclusions. A gradually increasing risk for a number of adverse pregnancy outcomes was found with increasing glucose levels. No obvious threshold value for GDM was demonstrated for 2‐h values up to 9.0 mmol/l.