Risk of T2DM Persists for Long After GDM Diagnosis
Introduction
Gestational diabetes mellitus (GDM) complicates nearly 6% of pregnancies and is a robust predictor of subsequent type 2 diabetes mellitus (T2DM). Nevertheless, there is less clarity on the association of the number of affected pregnancies and the T2DM risk as well as on the period for which this excess risk would persist, following the diagnosis of GDM.
Aim
- To evaluate the T2DM risk variation with body mass index (BMI) and the cumulative number of pregnancies affected by GDM
- To determine the changes over time in the age-specific relative risk of T2DM following a GDM diagnosis
Profile of the Study Participant
- Participants from the “Sister study” without diabetes at enrolment (n=47,471)
Methods
Study Design
- Observational study
Assessments
- Reproductive histories were assessed with respect to the risk of T2DM
- Cox proportional hazards models adjusted for BMI, educational level, and race/ethnicity, and that allowed the risk to depend on age, cumulative number of pregnancies with GDM, and time since the most recent affected pregnancy were used to determine the hazard ratios (HRs) for T2DM risk.
Results
- Of the entire study population, 1414 women reported at least one pregnancy with GDM. During the mean follow-up of 10.2 years, 3,180 women without a history of GDM (6.9%) and 190 women with GDM (13.4%) developed T2DM.
- History of one or more pregnancies with GDM was associated with an elevated age-specific risk of T2DM, at various time spans, the same being highest at 6–15 years after an affected pregnancy (Table 1).
|
Year Span after GDM Pregnancy |
HR |
95% confidence interval |
|
6-15 years |
3.87 |
2.60–5.75 |
|
16-25 years |
3.50 |
2.79-4.40 |
|
26-35 years |
1.95 |
1.46-2.61 |
|
After 35 years |
1.62 |
1.12-2.33 |
- Risk of T2DM (within 6-15 years of the last GDM pregnancy) increased steeply with multiple affected pregnancies (Table 2).
|
Years since last GDM Pregnancy |
Cumulative Number of GDM Pregnancies [HR (95% confidence interval)] | |||
|
0 (ref) |
1 |
2 |
>3 | |
|
6-15 Years |
1 |
3.46 (2.30-5.21) |
4.77 (2.93-7.77) |
7.15 (3.71-13.78) |
|
16-25 Years |
1 |
3.17 (2.48–4.06) |
4.37 (3.01–6.35) |
6.55 (3.69–11.61) |
|
26-35 Years |
1 |
1.78 (1.32–2.40) |
2.45 (1.60–3.77) |
3.67 (2.04–6.63) |
|
>35 years |
1 |
1.49 (1.03–2.17) |
2.06 (1.29–3.30) |
3.08 (1.60–5.94) |
- The age-specific associations attenuated over time after an affected pregnancy, with an estimated 24% reduction of the HR per decade. However, the risk remained high even after >35 years of GDM diagnosis.
Conclusions
- GDM was a robust predictor of the risk of T2DM in a large cohort of women.
- The age-adjusted relative risk of T2DM declined with time since the most recent GDM diagnosis, but remained elevated even after >35 years.
- Relative risk of T2DM also increased substantially with each additional affected pregnancy.
- Women with a history of GDM should be screened for T2DM on regular basis even late in life.
Diabetes Care 2022;45:864–870.
