Gestational Diabetes Mellitus - Diagnostic Implications during Pregnancy and follow-up
The overall objective of the present thesis was to assess diagnostic implications for diagnosis of gestational diabetes (GDM) during pregnancy (Papers I and V) and for diagnosis of type 2 diabetes at follow-up after pregnancy (Papers II and IV), and the relative contriubtions of maternal body mass index (BMI) and glucose levels in prediction of large-for-gestational-age (LGA) births (paper III).
PaperI: New diagnostic criteria have been proposed by the International Association of the Diabetes and Pregnancy Study Groups, which will increase the number of women diagnosed with GCM. Using the capillary 2-h glucose concentration from the oral glucose tolerance test (OGTT) as screening criterion for a repeat diagnostic OGTT, we found an increase in the frequency of GDM of 26% compared to the criteria currently used.
Paper II: Thresholds proposed by the World Health Organization for HbAic had low sensitivity in diagnosis of diabees an of abnormal glucose tolerance postpartum in the present study cohort. Combined with a fasting flucose test, the performance was no better than when using a fasting glucose test alone. Combination of a tasting glucose thest with a lower cut-point of HbAic may be an alternative approach to select women for a OGTT, in order to identify those who have isolated post-glucose load hyperglycemia.
Paper III: Maternal BMI had a greater impact on the prediction of LGA birth than the 2-h glucose level from the OGTT.
Paper IV: An HbA1c level of >36 mmol/mol, obtained close to the twenty-eighth week of pregnancy, was associated with a more than fivefold increased reisk of diabetes five years after pregnancy. A cut-off level for HbA1c of >mmol/mol, corresponding to the pre-diabetes range outside of pregnancy, could reveal women with postpartum diabetes with high specificity (97%) and high positive predictive value (91%). Due to the low sensitivity, HbA1c does not appear suitable as a screening test to predict diabetes after GCM in all women, but it could be used as a strategy for selecting high-risk women for lifestyle interventions to prevent diabetes, starting already in pregnancy.
Paper V: Based on the 2-h glucose lev el from a universally performed OGTT in the twenty-eighth week of pregnancy, seasonality in the proportion of women diagnosed with GDM was observed, with a peak in the summer. The mean 2-h-glucose concentrations bollowed the same seasonal trend.