Glucose Levels of the Oral Glucose Tolerance Test (oGTT) Can Predict Adverse Pregnancy Outcomes in Women with Gestational Diabetes (GDM)

Abstract

Objectives and Background: Gestational diabetes (GDM) is a common pregnancy complication, defined as a glucose intolerance diagnosis during pregnancy. GDM is strongly associated with adverse fetal and maternal outcomes. In Germany, to screen and diagnose GDM we use a 1-hour 50g oGCT (oral glucose challenge test) followed by a 2-hour 75g oGTT if the first was pathological. This analysis examines the correlation of 75g oGTT glucose levels and fetomaternal outcome. 
 Methods: 
 Data of 1664 patients from a gestational diabetes consultation clinic at the Charité University hospital in Berlin, Germany, were analyzed retrospectively from 2015 until 2022. The 75g oGTT blood glucose levels were categorized into isolated fasting hyperglycemia (GDM-IFH), isolated post-load hyperglycemia (GDM-IPH) and combined hyperglycemia (GDM-CH), using the levels of the fasting, 1-hour and 2-hour values after glucose application. These subtypes were compared regarding baseline characteristics as well as fetal and maternal outcome.
 Results: 
 GDM-IFH and GDM-CH women displayed higher preconceptional BMI and required insulin therapy more frequently (p<0,001). The GDM-IFH group was at higher risk of having a primary cesarean section (p=0,047), while GDM-IPH women were significantly more likely to have an emergent cesarean section (p=0,013). The offspring of GDM-IFH and GDM-CH women were born with a significantly higher mean birthweight (p<0,001) and birth weight percentiles (p<0,001) and were at increased risk of being large for gestational age (LGA) (p=0,004). Women from the GDM-IPH group delivered significantly more neonates who were small for gestational age (p=0,027) or with low fetal weight <30th percentile (p=0,003).
 Conclusion: 
 This analysis shows a strong association between glucose response pattern in the 75g oGTT and adverse perinatal fetomaternal outcome. The differences among the subgroups, specifically concerning insulin therapy, mode of delivery and fetal growth, suggest an individualized approach in prenatal care after a GDM diagnosis.