Diabetes risk after a normal oral glucose tolerance test during pregnancy

Abstract

Introduction: Our aim was to conduct a follow-up of a cohort of women screened for GDM with a normal oral glucose tolerance test (OGTT) during pregnancy to investigate the incidence and time of diagnosis of manifest diabetes mellitus and identify risk factors for subsequent development of diabetes.

Methods: This was a follow-up study of a cohort with normal and borderline OGTT in 1991/1992. Among the original 352 women, only five were lost to follow-up.

Results: In total, 64 women (18%) had manifest diabetes. Their median age was 57 years after 28 years of follow-up. This amounts to three times the expected rate compared with the background population. The rate of manifest diabetes rises 10-20 years after pregnancy and after the age of 40 years. A normal fasting glucose and also a borderline fasting glucose at OGTT during pregnancy were associated with an increased risk of manifest diabetes (p less-than 0.001), also after adjustment for age, Body Mass Index, non-Danish origin and smoking during pregnancy (p less-than 0.002).

Conclusion: The incidence of diabetes is higher in women with various risk factors for DM and a previously normal OGTT in pregnancy than in the background population. Our results are useful in identifying the time during which women may benefit from effective implementation of evidence-based treatment to postpone and avert manifest DM, even though they had a normal OGTT during pregnancy.

Funding: none.

Trial registration: The trial was registered with the the Regional Ethics Committee and the Data Protection Agency, nos. 2014-41-3433, 1-16-02-824-17 (under running permission no. 621549), 1-16-02-825-17, and 1-16-02-180-17, all under the cover of data handling agreement no. 509 with the Danish Health Authority.