Previous oral glucose tolerance test results as predictors of gestational diabetes mellitus in subsequent pregnancies: a retrospective cohort study.

Abstract

BACKGROUND: Although the oral glucose tolerance test (OGTT) is the gold standard for diagnosing gestational diabetes mellitus (GDM), its potential to predict GDM recurrence or occurrence in subsequent pregnancies remains insufficiently explored. This study aimed to determine whether OGTT results from a previous pregnancy could predict GDM risk in a subsequent pregnancy. METHODS: We conducted a retrospective cohort study using data from 11,397 women with two consecutive singleton pregnancies between January 2015 and July 2024, obtained from the Guangdong Women and Children Hospital. A 75-g OGTT was performed at 24–28 gestational weeks, with GDM diagnosed according to the International Association of Diabetes and Pregnancy Study Groups criteria. Logistic regression and restricted cubic spline models were used to assess associations between prior OGTT values (fasting, 1-hour, and 2-hour glucose levels) and subsequent GDM risk. Predictive performance was evaluated using receiver operating characteristic curve analysis. RESULTS: Elevated OGTT values (fasting, 1-hour, and 2-hour glucose levels) in the previous pregnancy were significantly associated with increased GDM risk in the subsequent pregnancy. Women with prior GDM had a markedly higher GDM incidence rate (51.6%) than those without prior GDM (10.6%). Combined hyperglycemia (elevated fasting and postprandial glucose) conferred the highest risk (adjusted OR: 16.21, 95% CI: 11.17–23.93), followed by isolated postprandial hyperglycemia (adjusted OR: 7.83, 95% CI: 6.85–8.98) and isolated fasting hyperglycemia (adjusted OR = 6.36, 95% CI: 4.64–8.68). OGTT values exhibited a J-shaped relationship with GDM risk. The model incorporating all three OGTT values demonstrated improved predictive accuracy (AUC: 0.82, 95% CI: 0.81–0.83). CONCLUSIONS: OGTT results from a previous pregnancy are strong predictors of GDM risk in subsequent pregnancies. These findings support the clinical use of routine OGTT data to identify high-risk women for targeted interventions, potentially reducing GDM recurrence and improving maternal-neonatal outcomes.