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Am J Perinatol 2023; 40(03): 243-249
DOI: 10.1055/s-0042-1758484
SMFM Fellowship Series Article

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

Samantha de los Reyes 
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, NorthShore University HealthSystem/University of Chicago Pritzker School of Medicine, Chicago, Illinois
,
Lavisha Singh
2   Department of Statistics, NorthShore University HealthSystem, Evanston, Illinois
,
Marci Adams
3   Department of Obstetrics and Gynecology, NorthShore University HealthSystem, Evanston, Illinois
,
Chi Wang
2   Department of Statistics, NorthShore University HealthSystem, Evanston, Illinois
,
Emmet Hirsch
4   Department of Obstetrics and Gynecology, NorthShore University HealthSystem/University of Chicago Pritzker School of Medicine, Evanston, Illinois
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Abstract

Objective 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.

Study Design 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.

Results 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.

Conclusion 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.

Key Points

  • 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.

Keywords

gestational diabetes - universal testing - targeted testing

Note

The findings in this paper were presented at the 2021 Virtual Society for Maternal Fetal Medicine Annual Meeting (January 25–31, 2021).


Supplementary Material



Publication History

Received: 14 April 2022

Accepted: 14 September 2022

Article published online:
25 November 2022

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