Diabetes Incidence Runs High After a Normal Pregnancy OGTT

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The study covered in this summary was published on ResearchSquare.com as a preprint and has not yet been peer reviewed.

Key Takeaways

  • Women with risk factors for gestational diabetes and a normal or borderline result from an oral glucose tolerance test (OGTT) during pregnancy were subsequently found to have a roughly threefold higher prevalence of diabetes compared with the general population.

  • Even in a population with a low incidence of type 2 diabetes, the risk of manifest diabetes is a potential outcome when classical diabetes risk factors exist. The results provide information on the prevalence, timing, and type of diabetes that developed later in life in relation to risk factors that occur earlier in life.

Why This Matters

  • Women who test negative for gestational diabetes should have follow-up screening to identify those with manifest diabetes who could benefit from earlier intervention to prevent diabetes-related complications.

Study Design

  • A retrospective, single-center, observational study that used data collected from 352 Danish women who underwent an OGTT while pregnant in 1991-1992. OGTT results were normal in 278 women and borderline in 74 women. The women underwent an OGTT because they had one or more risk factors for gestational diabetes: pre-pregnancy body mass index ≥ 27 kg/m2, family history of diabetes, glucosuria, multiple pregnancy, prior gestational diabetes, previous macrosomia (birth weight ≥ 4500 grams), or prior stillbirth. Each women underwent two OGTTs: the first occurred early in the second trimester, and the second in weeks 28-32.

  • At follow-up in 2021, the researchers reviewed medical, lab, and prescription records for the women for both their most recent status and historically during the period following their index pregnancy. Follow-up occurred a median of 28 years after the index pregnancy, when the women averaged 57 years old.

Key Results

  • Follow-up data were available for 347 women.

  • In the entire cohort, diabetes incidence during follow-up was 18%, threefold above the recent 6% diabetes incidence rate in the overall Danish population that is 50 to 60 years old. Median age at diabetes diagnosis was 50 years; 95% had type 2 diabetes.

  • Women with a borderline OGTT result developed manifest diabetes significantly sooner on average than those with a normal OGTT result.

  • In women with a borderline result, 20% had developed manifest diabetes at a median age of 50 after 22 years of follow-up. In women with a normal OGTT result, 15% had developed manifest diabetes by 28 years of follow-up, and 20% had manifest diabetes by the time they reached 61 years old.

  • Among the women who developed diabetes, 19% had thyroid disease, 73% had hypercholesterolemia, and 77% had cardiovascular disorders. All three comorbidities were prevalent at significantly higher rates compared with the women who did not develop diabetes.

  • Regression analysis showed that an elevated fasting glucose level at the time of their OGTT during pregnancy was significantly linked with subsequent development of diabetes both before and after adjusting for age, ethnicity, height, parity, smoking, and screening indications.

Limitations

  • Diagnosis of diabetes among the women may have been delayed both because the data came from electronic medical records and registries, and because clinicians may not have assessed for diabetes based only on risk factors in women younger than 40 years old after gestational diabetes had been ruled out during their pregnancies.

  • Fewer risk factors for gestational diabetes, especially a lower prevalence of obesity, existed in the Danish population in 1991-1992, when screening for gestational diabetes occurred in the study, and the diagnostic criteria for gestational diabetes applied at that time differed from more contemporary criteria.

  • About 10% of the women in the study did not undergo a second OGTT during pregnancy to confirm their gestational diabetes status.

Disclosures

  • The study did not receive any external funding.

  • None of the authors had disclosures.

This is a summary of a preprint research study, “Diabetes after pregnancy — a long-term follow-up in women with normal OGTT,” written by authors at Sønderjylland Hospital and Aabenraa Hospital, Denmark, on ResearchSquare.com provided to you by Medscape. This study has not yet been peer reviewed. The full text of the study can be found on ResearchSquare.com.

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