Abnormal Glucose Tolerance and Pregnancy Outcomes in Women Without Diagnosis of Gestational Diabetes

Objective: Maternal hyperglycemia and untreated gestational diabetes mellitus (GDM) lead to adverse perinatal outcomes. There is paucity of information in pregnant women with impaired glucose tolerance without gestational diabetes. This study aims to determine whether there are adverse perinatal outcomes amongst groups of women who rule in for abnormal glucose tolerance, but ultimately pass the diagnostic test, compared to women who have normal glucose tolerance and women with the diagnosis of GDM. Study Design: Retrospective cohort study of pregnant women who had a diabetic screening from January 2015 to April 2018 at the University of Illinois at Chicago (UIC). Singleton pregnancies that delivered at UIC were classified into 4 groups: normal 1h GCT (Group 1), abnormal 1h GCT only (Group 2), one elevated value on 3h GTT (Group 3), and GDM (Group 4). The primary outcome was LGA, with several adverse clinical outcomes as secondary outcome. Baseline characteristics and pregnancy outcomes of the four groups were compared. Chi square, Fisher exact test, one-way ANOVA and Student’s t-test were used. Bivariate and multivariate analysis were performed and the World Health Organization birth weight chart for LGA was used to assess gender-based fetal LGA. Result: Of the 6825 deliveries during the study period, 789 women met inclusion criteria. There were 206 women with abnormal 1h GCT only, 147 with one elevated value on 3h OGTT, 245 had normal 1h GCT and 191 diagnosed with GDM. The Group 4 (GDM) patients were significantly older, had a higher BMI, and had lower pregnancy weight gain (p value <0.001, <0.001, and 0.001 respectively). Race/ethnicity, presence of chronic hypertension (cHTN) and presence of asthma differed significantly between the four groups (p value: <0.001, 0.001, and 0.024, respectively). The mean 1h GCT for each group increased in a dose-dependent manner and was statistically different between Group 1, Group 2, Group 3, and Group 4 (104.8  17.0 mg/dl, 151.5  19.5 mg/dl, 158.1  15.0 mg/dl, and 165.6  20.8 mg/dl, respectively). A statistically significant, progressive trend was identified in risk of LGA for Group 2, Group 3, and Group 4 when compared to Group 1 as reference [RR of 3.93 (95% CI 1.05-14.64), 4.40 (95% CI 1.12-17.2), 6.24 (95% CI 1.70-22.94), respectively]. For every degree of increase in severity of glucose intolerance from Group 1 to Group 4, the neonatal birthweight increased by 38.23g (95% CI 3.28-73.18, p < 0.05). No differences existed in perinatal outcomes between Group 3 and Group 4. Conclusion: Patients with positive screen on 1h GCT, and with zero or only one elevated value on the 3h OGTT can similar adverse pregnancy outcomes as those with GDM. Our study shows that these screening results reflect a spectrum of glucose intolerance and these patients may require closer surveillance to improve pregnancy outcomes.