Poster Presentation Australasian Diabetes in Pregnancy Society Annual Scientific Meeting 2019

Estimating true prevalence of gestational diabetes in New Zealand: commonly used data sources result in significant variation (#53)

Robyn L Lawrence 1 , Clare R Wall 2 , Frank H Bloomfield 1
  1. The Liggins Institute, The University of Auckland, Auckland, New Zealand
  2. Department of Nutrition and Dietetics, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand

Aims: Prevalence of GDM varies depending on the population studied and the diagnostic criteria used.  Accurate estimation of GDM prevalence is important for service planning and evaluation, policy development, and research.  The aim of this study was to determine the prevalence of GDM in a cohort of New Zealand women using a variety of data sources and to evaluate the agreement between different data sources.

Methods:  Using a cohort of 6822 pregnant women enrolled in the Growing Up in New Zealand study, prevalence of GDM was estimated using four commonly used data sources.  Coded clinical data on diabetes status were collected from regional health boards and the Ministry of Health, plasma glucose results were collected from laboratories servicing the recruitment catchment area, and self-reported diabetes status collected via interview administered questionnaires.  Agreement between data sources was calculated using the proportion of agreement.  Results were compared to the prevalence of GDM calculated from the Ministry of Health’s National Minimum Dataset for women residing in the same geographical region as the Growing Up in New Zealand study catchment area and time-period.

Results:  The best estimate of prevalence of GDM in the Growing Up in New Zealand study using data from all data sources was 6.2%. However, estimates varied from 3.8% to 6.9% depending on the data source.  Prevalence of GDM in the National Minimum Dataset for the same region and time-period was 3.7%.  The proportion of agreement between data sources for presence of GDM was 0.70 (95% CI 0.65, 0.75).  A third (33.7%) of women who had a diagnosis of GDM according to medical data sources reported having no diabetes in interview administered questionnaires. 

Conclusions:  Prevalence of GDM varies considerably depending on the data source used, with significant implications for service planning and evaluation, policy development, and research.  Diagnosis of GDM was misreported by a large proportion of women; this is likely to have significant implications for women’s self-management of GDM.