Background Gestational diabetes mellitus (GDM) is associated with increased placental weight and the presence of placental malperfusion lesions, likely related to high blood glucose. The relationship between high glucose without overt GDM, and placental characteristics is not well understood.

Objective To examine the relationships between glucose challenge test (GCT) concentrations, GDM, and placental characteristics associated with GDM.

Methods We conducted a secondary analysis of medical record data from singleton placentas sent to pathology at Northwestern Memorial Hospital (2011-2022; n=11,585). Data included maternal demographic variables, GCT concentrations, GDM diagnosis, placental weight, and vascular malperfusion lesions (accelerated villous maturation, increased syncytial knots, delayed villous maturation, and increased perivillous fibrin deposition). We classified GCT <140 mg/dL as pass and ≥140 mg/dL as fail. We categorized glucose groups into pass GCT/no GDM, fail GCT/no GDM, and GDM. We used linear and Poisson regression models to examine the association between GCT concentrations or groups with placental outcomes, adjusting for maternal age, race and ethnicity, parity, gestational age at delivery, and infant sex.

Results Of placentas sent to pathology, 5% were from pregnancies with GDM and 17% from those who failed the GCT but did not get diagnosed with GDM. Compared to the pass GCT/no GDM group, the adjusted mean placental weight was heavier by 13.6 grams [95% CI: 8.8, 18.3] in the fail GCT/no GDM and 22.0 grams [13.8, 30.2] in the GDM group. Patients diagnosed with GDM had a 36% [2%, 81%] increased adjusted risk of delayed villous maturation compared to the pass GCT/no GDM. The risk of the other lesions was not statistically significantly different between groups.

Conclusion GDM and high glucose concentrations without GDM were associated with heavier placentas; patients with GDM had a higher risk of delayed villous maturation.

The authors have declared no competing interest.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Medical chart extraction was conducted as part of an existing multi-institution study with ethical approval through a single-IRB protocol at The Pennsylvania State University (IRB: STUDY00020697). Northwestern University was a participating site with a reliance agreement under the single-IRB.

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Data are available after the execution of a data use agreement with Northwestern University. Investigators should contact Dr. Goldstein, ja.goldsteinnorthwestern.edu.