Gestational diabetes: Glycaemic predictors for fetal macrosomia and maternal risk of future diabetes.

Aims: To investigate how glucose levels at diagnosis of gestational diabetes (GDM) are associated with infant birth weight and long-term risk of manifest diabetes mellitus in the mother.
Methods: In a case control study GDM pregnancies (n=2085) were compared with non-GDM pregnancies matched for day of delivery and obstetric unit (n=3792). GDM was defined as capillary blood glucose (cB-glucose) ≥9.0mmol/l (plasma glucose ≥10.0mmol/l) after a 75g oral glucose tolerance test (OGTT). The GDM cohort were followed up 8.5-13.5yrs after initial diagnosis with a questionnaire, answered by 1324 GDM women (65%).
Results: GDM women had higher mean infant birth-weight compared with controls (3682g vs. 3541g, P<0.001). In multiple linear regression analysis, birth weight was positively correlated to fasting cB-glucose at GDM diagnosis (P<0.001), increased week of gestation (P<0.001) and BMI before pregnancy (P<0.003), while 2h OGTT cB-glucose values ≥9.0mmol/l were not related. Infants born to mothers with fasting cB-glucose ≤4.5mmol/l had no increased mean birth-weight or macrosomia (≥4500g) compared to controls. In the follow up 334/1324 women (25%) of the GDM women had developed diabetes, 215 type 2 diabetes, 46 type 1 diabetes and 72 unclassified diabetes. In logistic regression fasting cB-glucose and 2h OGTT cB-glucose at diagnosis of GDM as well as BMI >25 and origin outside Europe were risk factors for manifest diabetes.
Conclusions: Fasting blood glucose at diagnosis of GDM gives important information besides 2h OGTT glucose about pregnancy outcome and future risk for maternal diabetes.
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