High-normal 50-gram glucose challenge test and future metabolic diseases: a population- based study

Objective
A 1-hour 50-gram glucose challenge test (GCT) is the first step in the screening for gestational diabetes mellitus (GDM). Accumulating evidence show that women with high- normal GCT levels are at elevated risk for immediate obstetric complications such as large for gestational age newborns and greater likelihood for caesarean delivery. We sought to examine the risk for metabolic disorders later in life, among women with high-normal GCT levels, as compared to low normal and abnormal GCT.

Study Design
This cohort study included all pregnant women who underwent GCT between the years 2005 to 2018 at the Central District of Clalit Health Services, the largest health maintenance organization in Israel. Rates of metabolic diseases (MTD) were compared between the three study groups: women with history of only Low-normal GCT (<124 mg/dL), High normal (125- 139 mg/dL) and abnormal GCT >140 mg/dL. Data on maternal ages and GCT results for each test performed, as well as MTD such as diabetes and obesity were collected and analyzed from the computerized database. Multivariable survival model was used to study the association between GCT levels and MTD risk, while adjusting for maternal age.

Results
A total of 66,869 women performed 1 to 10 GCTs to a total of 117,435 tests during the study period; 23% of study participants (n=15,360) had at least one abnormal result; 11.3% (n=7566) of participants had a diagnosis of MTD. As compared to women with low normal GCT (only), women with a history of high normal and abnormal GCT were at higher risk for MTD (10.4% vs. 12.4% and 13.0%, p<0.001, age adjusted HR=1.18; 95%CI 1.09-1.24, and 1.18; 95%CI 1.11-1.25, for high normal and abnormal GCT, respectively). There was no significant difference in MTD risk between women with history of high normal and abnormal GCT results (age adjusted HR=1.02; 95%CI 0.94-1.10; p=0.67).

Conclusion
As compared to women with low normal GCT, women with high normal GCT, similarly to women with abnormal GCT, are at increased MTD risk. Although GCT is a screening test, it may be a predictor of MTD later in life, and women with high normal GCT results may benefit from close monitoring of their metabolic status.