Rising Gestational Diabetes Rates Could Be Result of Changes in Screening Practices

Elizabeth Nethery, PhD
Courtesy: University of British Columbia

New research from a team in Canada suggests the apparent increases in gestational diabetes rates observed in recent years could be the result of changes in screening practices.

An analysis of more than 500,000 pregnancies over a 15-year period, results of the study indicate the rate of gestational diabetes doubled during the study period, but investigators purport this change could be the result of introducing newer, more effective screening practices.

"Despite concerns that a higher proportion of pregnant people with high BMIs, older maternal age or obstetric risk factors were leading to higher rates of gestational diabetes, these were not important contributors to the yearly increase in gestational diabetes in [British Columbia]," said lead investigator Elizabeth Nethery, School of Population and Public Health, University of British Columbia.²

In the face of reports detailing increasing rates of gestational diabetes in multiple regions throughout Canada, but the cause of this apparent increase not elucidated, Nethery and a team sought to estimate the impact of difference screening practices and population characteristics on risk of gestational diabetes among pregnancies in British Columbia, Canada from 2005-2019. With this in mind, investigators designed a population-based cohort study using data from the British Columbia Perinatal Data Registry. A validated, population-based registry, the database provided investigators with information related to more than 600,000 pregnancies occurring during the period of interest.¹

Limiting their cohort of interest to pregnancies with a first glucose tolerance fewest screening data between July 1, 2004 and June 30, 2019, investigators identified 551,457 pregnancies for inclusion in the current study. For the purpose of analysis, investigators designed their statistical model to predict annual risk for gestational diabetes, with sequential adjustment for screening completion, screening method, and demographic factors.¹

In 2010, International Association of Diabetes in Pregnancy Study Groups released a new guideline recommending a 1-step screening method, which called a for a single, 2-hour, 75-gram oral glucose tolerance test. However, the national guidelines in Canada, which were updated in 2013 and 2016, recommended a 2-step screening method: a 1-hour, 50-gram glucose challenge test followed by a 2-hour, 75-gram oral glucose tolerance test for patients who screen positive.¹

Initial analysis of the patient cohort indicated the coincidence of gestational diabetes had more than doubled during the study period, from 7.2% of pregnancies in 20-05 to 14.7% in 2019. During the study period, the rates of screening completion increased from 87.2% in 2005 to 95.5% in 2019. Investigators pointed out use of 1-step screening methods increased from 0.0% in 2005 to 39.5% in 2019, with the rate of 1-step screenings peaking in 2012 at 50.5%.¹

In unadjusted models, there was a more than 2-fold increase in risk of gestational diabetes in 2019 compared to 2005 (Relative risk [RR], 2.04 [95% confidence interval [CI], 1.94-2.13]). However, further analysis indicated this increase was mitigated after subsequent adjustment for the rise in screening completion (RR, 1.89 [95% CI., 1.81-1.98]) and changes in screening methods (RR, 1.34 [95% CI, 1.28-1.40]). In the final analytical model, which was adjusted for the aforementioned factors as well as demographic risk factors, the increase in risk of gestational diabetes was 25% (RR, 1.25 [95% CI, 1.19-1.31]).¹

"We need to look at gestational diabetes policies in [British Columbia], because screening changes alone are driving the substantial increase in diagnosis in our province. We need to make sure that any increase in diagnosis is truly beneficial to both patients and the health care system," Nethery added.²

References

1. Nethery E, Law MR, Kotaska A, et al. The effect of changing screening practices and demographics on the incidence of gestational diabetes in British Columbia, 2005–2019. Canadian Medical Association Journal. 2023. doi:doi.org/10.1503/cmaj.221404 Cmaj.
2. Increase in gestational diabetes rates linked largely to screening. EurekAlert! https://www.eurekalert.org/news-releases/982741. Published March 20, 2023. Accessed March 20, 2023.