Glucose Testing in an Index Pregnancy and Outcomes in a Subsequent Pregnancy: Implications for Screening and a Novel Risk Calculator.

Abstract

Our objective was to assess whether variables from an index pregnancy (PG1) can be used to guide testing for gestational diabetes mellitus (GDM) in a subsequent pregnancy (PG2) and to create a risk calculator for GDM in PG2. This was a retrospective cohort study of patients delivering ≥2 singleton gestations at >24 weeks' gestation from June 2009 to December 2018, for whom results of a 1-hour glucose challenge test (GCT) were available from PG1. Univariable and multivariable analyses were performed to evaluate factors associated with GDM in PG2. In total, 4,278 patients met the inclusion criteria. Among patients with a normal 1-hour GCT (<140 mg/dL) in PG1 (n = 3,719), 3.9% were diagnosed with GDM in PG2. In multivariable analysis of this group, GDM in PG2 was associated with higher GCT in PG1 (adjusted odds ratio [aOR]: 1.05, 95% confidence interval [CI]: 1.04-1.06), large for gestational age neonate in PG1 (aOR: 1.97, 95% CI: 1.24-3.13), and higher BMI (aOR: 1.08, 95% CI: 1.05-1.11). A novel risk calculator for GDM in PG2 was developed based on these associations. Using a risk cut-off of 15%, the calculator had a positive predictive value of 26% and a negative predictive value of 97%, with 3.2% of patients identified as "at risk". Among patients with abnormal 1-hour GCT in PG1, 38.3% (n = 214/559) had an abnormal 1-hour GCT in PG2 and 34.5% (n = 74/214) of these patients received a diagnosis of GDM. A normal 1-hour GCT in an PG1 is followed by GDM in a subsequent pregnancy in only 3.9% of cases. A novel calculator supports replacing universal screening with targeted testing in subsequent pregnancies in this population. Among patients with an abnormal 1-hour GCT in PG1, nearly 40% have an abnormal 1-hour GCT in a subsequent pregnancy. Direct diagnostic testing can be considered in such patients. · Normal GCT in a first pregnancy is associated with normal GCT in subsequent pregnancy.. · A risk calculator can target diabetes testing in a subsequent pregnancy.. · Abnormal GCT in a first pregnancy is associated with abnormal GCT in subsequent pregnancy..