Clinical importance of the 75-g glucose tolerance test (GTT) in the prediction of large for gestational age (LGA) fetuses in non-diabetic pregnancies

Abstract

Abstract Objective To demonstrate clinical importance of the 75-g glucose tolerance test (GTT) in the prediction of large for gestational age (LGA) fetuses in non-diabetic pregnancies. Methods We retrospectively evaluated 75-g GTT screening results of 356 pregnancies without prompt diagnosis of gestational diabetes mellitus (GDM) between January 2013 and December 2017. Newborns with a birthweight greater than the 90th percentile were evaluated as LGA. Pregnancies with LGA and non-LGA fetuses were compared by demographic and historical factors – maternal age, gravidity, parity, birthweight, birthweek, GTT results and birthweight percentiles – via Student’s t-test. Multiple linear regression using the backward elimination method was performed to define the correlation between parameters and LGA (P-value of <0.20 was identified as the threshold). Receiver operator characteristics (ROC) curve analysis was performed for further analysis. Results The cohort was consisted of 45 (12.6%) and 311 (87.4%) pregnancies with LGA and non-LGA fetuses, respectively. Maternal age and 2nd-h GTT results were found to be significantly higher in patients with LGA newborns (P<0.001 and P=0.016, respectively). Fasting glucose levels and GTT 1st-h results were also higher (P=0.112, P=0.065). The coefficient of multiple determination (R2) was 0.055 by multiple linear regression analysis. Accordingly, GTT 2nd-h result and maternal age were statistically significant and contributed to the explanation of LGA, although the R2 value was not that much higher (P=0.016; P=0.001). Maternal age and GTT 2nd-h results were found to be associated with LGA fetuses with area under the curve (AUC) values of 0.662 and 0.608 according to ROC curve analysis. Conclusion Maternal age and 75-g GTT 2nd-h results were significantly higher in gestations with LGA newborns without GDM.