Sociodemographic correlates of the increasing trend in prevalence of gestational diabetes mellitus in a large population of women between 1995 and 2005

OBJECTIVE—Gestational diabetes mellitus (GDM) is an increasingly prevalent risk factor for the development of type 2 diabetes in the mother and is responsible for morbidity in the child. To better identify women at risk of developing GDM we examined sociodemographic correlates and changes in the prevalence of GDM among all births between 1995 and 2005 in Australia''s largest state.RESEARCH DESIGN AND METHODS—A computerized database of all births (n = 956,738) between 1995 and 2005 in New South Wales, Australia, was used in a multivariate logistic regression that examined the association between sociodemographic characteristics and the occurrence of GDM.RESULTS—Between 1995 and 2005, the prevalence of GDM increased by 45%, from 3.0 to 4.4%. Women born in South Asia had the highest adjusted odds ratio (OR) of any region (4.33 [95% CI 4.12–4.55]) relative to women born in Australia. Women living in the three lowest socioeconomic quartiles had higher adjusted ORs for GDM relative to women in the highest quartile (1.54 [1.50–1.59], 1.74 [1.69–1.8], and 1.65 [1.60–1.70] for decreasing socioeconomic status quartiles). Increasing age was strongly associated with GDM, with women aged >40 years having an adjusted OR of 6.13 (95% CI 5.79–6.49) relative to women in their early 20s. Parity was associated with a small reduced risk. There was no association between smoking and GDM.CONCLUSIONS—Maternal age, socioeconomic position, and ethnicity are important correlates of GDM. Future culturally specific interventions should target prevention of GDM in these high-risk groups.Type 2 diabetes affects an estimated 246 million individuals worldwide—a figure that is predicted to increase to 380 million by 2025, with a disproportionate number of affected individuals living in lower- and middle-income countries of the Asia-Pacific region (1). Diabetes is a major cardiovascular risk factor, more than doubling the risk of having a stroke or heart attack. Moreover, diabetes appears to be particularly hazardous in women, as there is a 50% greater risk of dying from coronary heart disease compared with that of men with the same condition (2).Gestational diabetes mellitus (GDM), defined as glucose intolerance first detected during pregnancy, is a strong predictor of type 2 diabetes. Women with GDM are up to six times more likely to develop type 2 diabetes than women with normal glucose tolerance in pregnancy (3). The incidence of GDM varies among populations, similar to the variation of type 2 diabetes, with recent prevalence estimates ranging from 2.8% of pregnant women in Washington, DC, to 18.9% in India and 22% in Sardinia, Italy (4). The risk for GDM increases with age, and incidence rates vary by ethnicity within a population, again similar to the risk for type 2 diabetes (4,5). There is also evidence that obesity, parity, smoking, and family history are risk factors for GDM (5). However, less is known regarding the sociodemographic distribution of GDM. Given the strong link between GDM and the subsequent risk of diabetes for the mother and the perinatal morbidity for mother and child—an association recently updated with findings of a continuous association of maternal glucose levels and adverse perinatal outcomes by the Hyperglycemia and Adverse Pregnancy Outcomes Study Cooperative Research Group (6)—a better understanding of the sociodemographic determinants of GDM may provide novel opportunities to reduce the incidence and to prevent the onset of type 2 diabetes in later life.Most studies that have examined the etiology of GDM have been hospital based or have been based on samples of births in a particular region (4,5). There are currently no large, comprehensive population-wide urban and rural datasets that have been collected in an attempt to examine multiple risk factors for GDM over a number of years and no population-based studies outside the U.S. The New South Wales (NSW) Midwives Dataset has information on nearly 1 million births in the state of NSW during the period from 1995 to 2005 in a health system in which there is almost universal screening for GDM. This dataset was used to study the current and changing population rates of GDM and its associated sociodemographic risk factors in a large, ethnically diverse population of women.