Background: Advanced glycation end products (AGEs) accumulate with age and in diabetes mellitus (DM). AGEs can be measured by the AGE Reader (DiagnOptics Technologies BV, Groningen, The Netherlands) using skin autofluorescence (SAF). SAF is related to chronic diabetes complications. In a previous study we reported that SAF is comparable in patients with gestational DM (GDM) and controls at 27 weeks of gestation. In the current study we investigated SAF at multiple time points during pregnancy in pregnancies complicated by DM (type 1 or type 2) or GDM and in controls. Furthermore, the relation between SAF levels and adverse pregnancy outcomes was investigated. Subjects and Methods: In this single-center prospective observational study SAF was measured during pregnancy from 26 gestational weeks onward in 79 GDM patients, 21 patients with preexistent DM (type 1 or type 2), and 55 women without diabetes. Adverse pregnancy outcomes were recorded. Results: SAF decreased slightly but significantly (β=-0.018) during normal pregnancy but not in pregnancies complicated with hyperglycemia. At the end of pregnancy SAF was higher in patients with preexistent DM (1.91 arbitrary [AU] units) compared with patients with GDM (1.71 AU) or normal pregnancy (1.66 AU) but did not differ between the latter two groups. SAF was not related to adverse pregnancy outcomes. Conclusions: The decrease in SAF during normal pregnancy could be the result of physiological changes. Because SAF was not related to adverse pregnancy outcomes, it is unlikely that the AGE Reader will be of use in daily clinical practice for GDM patients as a marker for identifying high-risk pregnancy outcomes.