Pre-diabetes, diabetes and fluctuations of glucose tolerance after gestational diabetes mellitus: 5-year follow-up of a contemporary, prospective study in Germany

Abstract

Introduction: Ten years ago, Germany started offering screening for gestational diabetes mellitus (GDM) to all pregnant women. This approach revealed more but also, on average, less severe cases of GDM than the risk-based screening practiced previously. We now examined the incidence of pre-diabetes and diabetes following a GDM diagnosis in the era of universal screening in Germany and compared our results with studies in the previous period. Additionally, we examined the year-to-year fluctuations of glucose tolerance after a pregnancy complicated by GDM.

Research design and methods: We report 5-year follow-up data from 202 women in the prospective, monocenter, postpartum study PPSDiab. Consecutive recruitment took place in Munich, Germany between 2011 and 2016. In the study, we conducted yearly examinations that included anthropometrics, laboratory chemistry and oral glucose tolerance testing.

Results: During the first 5 years post partum, 111 (55%) and 12 (6%) of the women developed pre-diabetes and type 2 diabetes, respectively, while 2 (1%) developed type 1 diabetes. Impaired fasting glucose (IFG) was the most common first manifestation of disturbed glucose tolerance, followed by impaired glucose tolerance (IGT), the combination of IFG and IGT, and diabetes. Glucose tolerance did not deteriorate steadily in most women but fluctuated from year to year.

Conclusions: In our analysis, the incidence of diabetes, both type 1 and type 2, after GDM diagnosed in universal screening was substantially lower than in studies from the previous period of risk-based screening. Nevertheless, the high incidence of pre-diabetes we observed after GDM still confirms the importance of this diagnosis as a risk marker. Additionally, we documented frequent fluctuations of glucose tolerance from 1 year to the next. Therefore, a single postpartum glucose tolerance test, as currently practiced in routine care, may be insufficient for reliable risk stratification after GDM.

Keywords: cohort studies; diabetes mellitus; gestational diabetes mellitus; pre-diabetic state; type 2.

Figure 1

Flow chart of the 5-year follow-up of the PPSDiab Study. The primary study endpoint was defined as the diagnosis of type 2 diabetes (T2D) by OGTT. Participants during an additional pregnancy and up to 6 months post partum (p.p.) did not attend study visits for OGTT. GDM, gestational diabetes mellitus; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; NGT, normal glucose tolerance; OGTT, oral glucose tolerance test.

Figure 2

Cumulative incidence of pathologic OGTT results during 5 years post partum. Only the first pathologic test was counted for each woman. The black line represents the total count of all categories. IFG, impaired fasting glucose; IGT, impaired glucose tolerance; OGTT, oral glucose tolerance test; T2D, type 2 diabetes.

Figure 3

Intraindividual fluctuations of glucose tolerance during 5 years post partum (p.p.). Vertical bars mark the yearly study visits. Colors represent the status of glucose metabolism with green=normal glucose tolerance (NGT), light blue=isolated impaired fasting glucose (IFG), dark blue=isolated impaired glucose tolerance (IGT), orange=combined IFG and IGT (IFG+IGT), red=type 2 diabetes (T2D) equivalent to study endpoint, gray=invalid or no OGTT. Line width represents the number of participants following each trajectory. OGTT, oral glucose tolerance test.