Flat Oral Glucose Tolerance Test during Pregnancy and Risk for Type 2 Diabetes: A 5-Year Cohort Study

Abstract

Objective

This study aimed to evaluate the risk of type 2 diabetes mellitus (T2DM) in women with flat response in the 100-g oral glucose tolerance test (OGTT) performed during pregnancy in a large cohort of women with up to 5 years of follow-up.

Study Design

A retrospective analysis of women with documented OGTT during pregnancy and T2DM data up to 5 years after pregnancy. Gestational diabetes mellitus (GDM) screening was done by a two-step strategy. Glucose levels during pregnancy were extracted from the computerized laboratory system of Meuhedet Health Maintenance Organization (HMO) and cross-tabulated with the Israeli National Diabetes Registry. Flat OGTT was defined as fasting glucose <95 mg/dL and three postprandial values lower than 100 mg/dL. The cohort was stratified by OGTT results to normal glucose values, flat OGTT, and GDM according to Carpenter and Coustan thresholds. Cumulative risk for T2DM was evaluated and compared between groups. Statistical analysis included univariate analysis followed by survival analysis.

Results

A total of 14,122 parturients entered the analysis. Of them, 965 (6.8%) had flat OGTT, 11,427 (80.9%) had normal OGTT, and 1,730 (12.3%) had GDM. Women with flat OGTT were younger, had lower body mass index (BMI; kg/m²), and had lower rates of hypertension. Their glucose values throughout pregnancy were lower compared with the other groups (p < 0.001 for all). During the study period and following adjustment to maternal age, obesity, and hypertension, women with flat OGTT had a low incidence of T2DM, even when compared with women with normal OGTT (adjusted hazard ratio 0.212, 95% confidence interval 0.052–0.856).

Conclusion

Parturients with flat OGTT during pregnancy are at a low risk of developing T2DM up to 5 years following pregnancy.

Key Points

• Women with flat OGTT are younger, with lower BMI and lower hypertension rates.

• During pregnancy, glucose levels were lower in flat OGTT women than in normal OGTT or GDM.

• Postpartum women with flat OGTT had lower risk of developing type 2 diabetes over 5 years.

Keywords

diabetes mellitus - gestational diabetes - pregnancy - oral glucose tolerance test - flat OGTT

Ethical Approval

The study was approved by the Meuhedet Institutional Review Board committee (10-18-08-21). Due to the retrospective nature of the study, informed consent was waived. The study was performed in accordance with the Declaration of Helsinki.

Authors' Contributions

D.T. and A.N. wrote, reviewed, and edited the manuscript. R.G-B. and E.M-S. researched data, contributed to the discussion, and reviewed and edited the manuscript. All authors approved the final version of the manuscript. M.H. reviewed and edited the manuscript.

R.G-B. is the guarantor of this work and, as such, has full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

^* These authors should be considered co-authors and contributed equally to this work.

Publication History

Received: 18 June 2024

Accepted: 26 November 2024

Accepted Manuscript online:
28 November 2024

Article published online:
24 December 2024

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