Maternal and Neonatal Outcomes with One Abnormal Value on 100g Three Hour Glucose Tolerance Test in Pregnancy

Abstract

Purpose: The primary objective of this study was to compare pregnancy outcomes for patients with no elevated glucose values, one elevated glucose value, and 2 or more elevated glucose values on the 3-hour glucose tolerance test (GTT). Methods: This was a retrospective chart review of obstetric patients seen by residents and attending physicians at a single institution from 2015 to 2020 who were required to complete a 3-hour glucose tolerance test (GTT). Data extracted from the maternal chart included demographic information, BMI, route of delivery, presence of preeclampsia, chorioamnionitis, shoulder dystocia and preterm labor. Data extracted from the neonatal chart included blood glucose level after birth, birth weight, Apgar scores, and if NICU admission was required. Continuous data were analyzed using one-way ANOVA to compare the 3 groups, followed by post-hoc Tukey HSD to compare the 1 abnormal value group to the control group. Dichotomous data were analyzed using Chi square tests. Logistic regression was performed using shoulder dystocia as the outcome. Results: Patients with two or more elevated GTT values had higher age and BMI and were more likely to be prescribed diabetic medications compared to those with normal or one elevated value. They were also more likely to deliver at an earlier gestational age. Patients with one elevated GTT value experienced a statistically significant higher chance of shoulder dystocia compared to patients with all normal GTT results (OR 2.34; 95% CI 1.05, 5.20). Patients with two or more elevated values were more likely to have preeclampsia and a neonate requiring NICU admission. There were no differences in cesarean delivery rate, hemorrhage or chorioamnionitis between the groups. Conclusions: Patients with one elevated GTT value are a special subset of patients who do not meet criteria for gestational diabetes, yet do not have normal glucose testing results. We hypothesize that this group is at higher risk of shoulder dystocia because these patients may have hyperglycemia but often do not receive the same type of monitoring, dietary education, medication initiation and induction timing as patients who meet criteria for gestational diabetes.