(313) Risk Factors, Not Late OGTT, Predict Adverse Outcomes After a Normal GCT

Large-for-gestational-age (LGA) fetus or polyhydramnios are considered relative indications for third-trimester oral glucose tolerance test (OGTT) even after a normal glucose challenge test (GCT). The clinical significance of late-diagnosed gestational diabetes (GDM) remains unclear. We aimed to evaluate the utility of late OGTT in this population and its association with adverse outcomes, considering maternal diabetic risk factors.

Study Design:

This retrospective cohort included 585 singleton pregnancies (2018–2021) with normal GCT who underwent late OGTT ( >28 weeks) in a university-affiliated center. GDM was diagnosed by the two-step strategy based on the Carpenter and Coustan criteria (≥2 abnormal values). Women were stratified according to the diagnosis of late GDM, followed by a second analysis into four groups based on OGTT results and presence of diabetic risk factors (BMI >30 kg/m², family history of diabetes, prior GDM or macrosomia). Outcomes included cesarean delivery (CD), LGA, macrosomia, and birthweight. Univariate analysis was followed by a multivariable analysis to adjust for confounders.

Results:

Among 585 women, 134 (22.9%) were diagnosed with GDM. GDM cases had lower PAPP-A and higher first-trimester fasting glucose levels. They delivered earlier (38.9 vs. 39.3 weeks) with lower birthweights (3437 vs. 3536 g) and lower macrosomia rates (7.5% vs. 15.1%), p< 0.05 for all. Nevertheless, CDs were more frequent in the GDM group, mainly for suspected macrosomia. In the second analysis, LGA rates were similar between women without GDM and those with GDM plus risk factors (35–39%), but lowest in GDM without risk factors (17.9%, p=0.03). In the multivariate analysis, only diabetic risk factors—not OGTT positivity—predicted CD (aOR 2.09, 95% CI 1.3–2.1, p< 0.001).

Conclusion:

Overall, a late OGTT after a normal GCT did not identify additional risk for macrosomia or LGA. Only for women with diabetic risk factors, late GDM was associated with higher CD rates. These findings support a risk-based approach to third-trimester OGTT even in the presence of LGA or polyhydramnios.