Screening gestational diabetes mellitus: The role of maternal age

Abstract

Objective: Using a specific cutoff of fasting plasma glucose (FPG) to screen gestational diabetes mellitus (GDM) can reduce the use of oral glucose tolerance tests (OGTT). Since the prevalence of GDM increases with age, this screening method may not be appropriate in healthcare systems where women become pregnant at older ages. Therefore, we aimed to develop a screening algorithm for GDM that takes maternal age into consideration.

Methods: We included 945 pregnant women without history of GDM who received 75g OGTT to diagnose GDM in 2011. Screening algorithms using FPG with or without age were developed. Another 362 pregnant women were recruited in 2013-2015 as the validation cohort.

Results: Using FPG criteria alone, more GDM diagnoses were missed in women ≥35 years than in women <35 years (13.2% vs. 5.8%, p <0.001). Among GDM women ≥35 years, 63.6% had FPG <92 mg/dL (5.1 mmol/L). Use of the algorithm with an "age plus FPG" cutoff could reduce the use of OGTT (OGTT%) from 77.6% to 62.9%, while maintaining good sensitivity (from 91.9% to 90.2%) and specificity (from 100% to 100%). Similar reduction in OGTT% was found in the validation cohort (from 86.4% to 76.8%). In the simulation, if the percentage of women ≥35 years were 40% or more, the screening algorithm with an "age plus FPG" cutoff could further reduce OGTT% by 11.0%-18.8%.

Conclusions: A screening algorithm for GDM that takes maternal age into consideration can reduce the use of OGTT when women become pregnant at older ages.

Fig 1. The prevalence of Gestational Diabetes Mellitus (GDM) with Fasting Plasma Glucose (FPG) <92 mg/dL (5.1 mmol/L) in pregnant women by age in the training cohort.

Women who have GDM with FPG <92 mg/dL (5.1 mmol/L) will be missed if only FPG is checked. GDM, gestational diabetes mellitus; FPG, fasting plasma glucose.

Fig 2

Algorithm (A) A and (B) B to screen gestational diabetes mellitus. The percentages of pregnant women in the training cohort are shown. Age + FPG, age in years plus fasting plasma glucose in mg/dL (plasma glucose in mg/dL = plasma glucose in mmol/L * 18). FPG, fasting plasma glucose; GDM, gestational diabetes mellitus; OGTT, oral glucose tolerance tests; GDM excluded, pregnant women who were diagnosed as not having GDM; GDM diagnosed, pregnant women who were diagnosed as GDM.