Low normal glucose tolerance test as a predictor of small for gestational age infants

The glucose tolerance test (GTT) is the gold standard for diagnosing gestational diabetes mellitus (GDM), treatment of which can reduce maternal and fetal complications. While emphasis is placed on monitoring and treatment following an elevated one hour GTT ( >=135 mg/dL), low results (< = 95 mg/dL) could be associated with placental insufficiency. We evaluated the association between small for gestational (SGA) infants and low normal one-hour GTT screening tests. A retrospective cohort study of all singleton pregnancies with a normal screening one-hour GTT (<135 mg/dL) was performed at a single institution from 2013-2020. Results of the GTT were stratified by either normal GTT (96-135 mg/dL) or low normal GTT (< /= 95 mg/dL). Logistic regression was used to calculated adjusted odds ratios (aOR) and 95% confidence intervals (CI) for SGA adjusting for maternal age, race, BMI, and chronic hypertension. A total of 7,069 pregnancies with normal screening GTT results were included in the analysis with 2,589 (36.6%) classifying as a low normal GTT. Women with a low normal GTT were more likely to be younger, use tobacco, be of non-Hispanic black race, have a higher BMI, and have chronic hypertension (Table 1). Overall, 13.1% of infants in the low normal OGTT cohort were found to be SGA compared to 9.5% in the normal GTT cohort (aOR 1.3, CI 1.1-1.5). Despite higher rates of SGA, there were lower rates of preeclampsia (aOR 0.69, CI 0.53-0.90) in women with a low normal GTT. A low 1-hour GTT is associated with increased odds of SGA, but decreased odds of preeclampsia. This could represent the effects of a relative glucose deficiency with lower hyperglycemia mediated hypertension.View Large Image Figure ViewerDownload Hi-res image Download (PPT)