1194: Atypical response to glucose challenge test in pregnancy is associated with small-for-gestational age birth weight

Disturbances in maternal metabolism directly influence glucose availability for fetal growth and energy. The aim of this study was to identify those levels of the 1hr GCT associated with small for gestational age (SGA) neonates. We hypothesize that an atypical response to the 1hr GCT between 24-32 wga will be correlated with SGA. In this prospective, observational study, 1347 adult patients enrolled in prenatal care from 6/2016-9/2019 at a tertiary referral center underwent 1hr GCT between 24-32 wga. Data collected included: demographics, maternal pre-pregnancy BMI, total weight gain (TWG), comorbidities, Hemoglobin (Hb) A1c levels, and neonatal outcomes. Patients with multiple gestations, gestational diabetes, and incomplete records were excluded. SGA was defined as birth weight < 10th centile. A low 1hr GCT was categorized as < 1 SD below the mean. Multivariate logistic regression was used to compare 1hr GCT levels in SGA vs. non SGA pregnancies with respect to BMI and TWG. The 990 patients meeting inclusion criteria had a mean 1hr GCT of 101.8 (SD +/- 23.5). In addition, 152 (15%) of the patients had SGA neonates. The mean 1hr GCT was lower in SGA neonates (102.8 + 23.4 vs. 96.9 + 23.5, p= 0.003). No difference was seen in HbA1c (5.13 + 0.35 vs. 5.08 + 0.36, p = 0.136) or BMI between groups (p >0.05). However, SGA pregnancies had significantly decreased TWG (7.7kg vs 9.9kg). Patients with a 1hr GCT < 79 (-1 SD) had significantly increased association with SGA [aOR: 1.9 (95% CI: 1.1-3.3)]. SGA has many etiologies including genetic syndromes, in-utero infection, and utero-placental insufficiency. Our study suggests that screening gravidas with a 1hr GCT may detect those at risk for decreased fetal growth. Additional studies are needed to understand how this variant in maternal glucose metabolism influences the development of SGA fetuses.