A population-based observational study of diabetes during pregnancy in Victoria, Australia, 1999-2008.
OBJECTIVE
This paper reports secular trends in diabetes in pregnancy in Victoria, Australia and examines the effect of including or excluding women with pre-existing diabetes on gestational diabetes (GDM) prevalence estimates.


METHODS
Population-based observational study.


METHODS
All births in Victoria, Australia between 1999 and 2008 PARTICIPANTS: 634,932 pregnancies resulting in a birth registered with the Victorian Perinatal Data Collection


METHODS
Crude and age-standardised secular trends in pre-existing diabetes and GDM prevalence; secular GDM trends by maternal birthplace; effects on GDM prevalence of including and excluding pre-existing diabetes from the denominator.


RESULTS
Of the 634,932 pregnancies, 2954 (0.5%) occurred in women with pre-existing diabetes and 29,147 (4.6%) were complicated by GDM. Mean maternal age increased from 29.7 years in 1999 to 30.8 years in 2008. GDM prevalence increased in most maternal age groups. In 2008, age-standardised GDM prevalence was 31% higher than in 1999; secular increases were greater for Australian-born non-Indigenous (29% increase) than immigrant women (12.3% increase). The annual number of pregnancies in women with pre-existing diabetes almost doubled from 1999 to 2008 and prevalence increased from 0.4% to 0.6%. However, including or excluding pre-existing diabetes had little effect on GDM prevalence estimates.


CONCLUSIONS
Pre-existing diabetes and GDM prevalence increased in Victoria between 1999 and 2008 and rising maternal age does not fully explain these trends. These findings have important implications for preventive initiatives. Including or excluding small numbers of women with pre-existing diabetes resulted in minimal changes in GDM estimates. As pre-existing diabetes in young women increases, this methodological issue will likely become important.
Greater Green Triangle University Department of Rural Health, Flinders and Deakin Universities, Warrnambool, Victoria, Australia Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Victoria, Australia.
Marian
M
Abouzeid
Greater Green Triangle University Department of Rural Health, Flinders and Deakin Universities, Warrnambool, Victoria, Australia.
Vincent L
VL
Versace
Greater Green Triangle University Department of Rural Health, Flinders and Deakin Universities, Warrnambool, Victoria, Australia Department of Medicine, Northwest Academic Centre, The University of Melbourne and Western Health, Melbourne, Victoria, Australia.
Edward D
ED
Janus
Consultative Council on Obstetric and Paediatric Mortality and Morbidity, Clinical Councils Unit, Department of Health, Melbourne, Victoria, Australia Judith Lumley Centre, La Trobe University, Melbourne, Victoria, Australia.
Mary-Ann
MA
Davey
Greater Green Triangle University Department of Rural Health, Flinders and Deakin Universities, Warrnambool, Victoria, Australia.
Benjamin
B
Philpot
Consultative Council on Obstetric and Paediatric Mortality and Morbidity, Clinical Councils Unit, Department of Health, Melbourne, Victoria, Australia Melbourne School of Population and Global Health, The University of Melbourne, Melbourne, Victoria, Australia.
Jeremy
J
Oats
Greater Green Triangle University Department of Rural Health, Flinders and Deakin Universities, Warrnambool, Victoria, Australia.
James A
JA
Dunbar
D000328:Adult; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D016640:Diabetes, Gestational / Q000453:epidemiology*; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D011254:Pregnancy in Diabetics / Q000453:epidemiology*; D015995:Prevalence; D014739:Victoria / Q000453:epidemiology; D055815:Young Adult
PREVENTIVE MEDICINE; PUBLIC HEALTH