Type 1 and type 2 diabetes after gestational diabetes: a 23 year cohort study

Abstract

Aims/hypothesis: The aim of this work was to examine the progression to type 1 and type 2 diabetes after gestational diabetes mellitus (GDM) in a 23 year follow-up study.

Methods: We carried out a cohort study of 391 women with GDM diagnosed by an OGTT or the use of insulin treatment during pregnancy, and 391 age- and parity-matched control participants, who delivered in 1984-1994 at the Oulu University Hospital, Finland. Diagnostic cut-off levels for glucose were as follows: fasting, ≥4.8 mmol/l; 1 h, ≥10.0 mmol/l; and 2 h, ≥8.7 mmol/l. Two follow-up questionnaires were sent (in 1995-1996 and 2012-2013) to assess the progression to type 1 and type 2 diabetes. Mean follow-up time was 23.1 (range 18.7-28.8) years.

Results: Type 1 diabetes developed (5.7%) during the first 7 years after GDM pregnancy and was predictable at a 2 h OGTT value of 11.9 mmol/l during pregnancy (receiver operating characteristic analysis: AUC 0.91, sensitivity 76.5%, specificity 96.0%). Type 2 diabetes increased linearly to 50.4% by the end of the follow-up period and was moderately predictable with fasting glucose (AUC 0.69, sensitivity 63.5%, specificity 68.2%) at a level of 5.1 mmol/l (identical to the fasting glucose cut-off recommended by the International Association of Diabetes and Pregnancy Study Groups [IADPSG) and WHO]).

Conclusions/interpretation: All women with GDM should be intensively monitored for a decade, after which the risk for type 1 diabetes is minimal. However, the incidence of type 2 diabetes remains linear, and therefore individualised lifelong follow-up is recommended.

Keywords: GDM; Insulin; OGTT; Prediction; Type 1 diabetes; Type 2 diabetes.

Fig. 1

Probability of remaining free from (a) diabetes, (b) type 1 diabetes or (c) type 2 diabetes among women with and without GDM. Logrank p < 0.001 in all figure parts. Mean (95% CI) diabetes-free survival time in women with vs without GDM was as follows: diabetes, 21.5 (20.5, 22.4) years vs 29.6 (29.3, 29.9) years; type 1 diabetes, 26.7 (25.8, 27.5) years vs no occurrence of type 1 diabetes; and type 2 diabetes, 22.6 (21.7, 23.5) years vs 29.6 (29.3, 29.9) years

Fig. 2

Probability of remaining free from (a) type 1 diabetes and (b) type 2 diabetes according to the number of pathological glucose values in OGTT during the GDM pregnancy. Logrank p < 0.001. Mean (95% CI) type 1 diabetes-free survival time was as follows: one pathological value, no occurrence of type 1 diabetes; two pathological values, 28.2 (27.5, 29.0) years; three pathological values, 21.4 (18.8, 24.0) years. Mean (95% CI) type 2 diabetes-free survival time was as follows: one pathological value, 25.0 (23.8, 26.1) years; two pathological values, 24.3 (22.9, 25.8) years; three pathological values, 17.9 (16.2, 19.6) years