Addressing gestational diabetes among Aboriginal and Torres Strait Islander women

Abstract

Gestational diabetes mellitus (gestational diabetes) is increasing, with Indigenous populations particularly affected; causing serious complications in pregnancy, birth, and in the longer term for women and their children. Importantly, exposure to diabetes in-utero increases the diabetes risk for the infant, causing a compounding intergenerational effect. Recent gestational diabetes guidelines have particular implications for Aboriginal and Torres Strait Islander (Aboriginal) women, who are categorised as ‘high risk’ and advised to have screening in early pregnancy, in addition to 24–28 weeks as previously recommended. The aim of this thesis is to examine the extent to which the public health challenges posed by gestational diabetes are being met for Aboriginal and Torres Strait Islander women. A systematic review of the evidence for early screening for gestational diabetes among Indigenous women in Australia, Canada, New Zealand and the United States found the majority of studies describe high prevalences among Indigenous women, and high rates of complications for Indigenous women and their infants during pregnancy, birth, and the longer term. However, there is limited evidence of acceptable and effective screening, treatment, postpartum follow-up, or prevention for Indigenous women. Studies included in this thesis addressed evidence gaps identified in this review. The first study analysed national gestational diabetes trends among Aboriginal and non-Aboriginal women from 1990 to 2009, using midwives perinatal data. Crude and age-adjusted prevalences were higher in Aboriginal than non-Aboriginal women at all time-points (4.7% versus 3.1% in 1990–1999; 5.1% versus 4.5% in 2000–2009, p<0.0001). From 2000–2009, gestational diabetes prevalence increased significantly among Indigenous women by a mean 2.6% annually (ptrend<0.0001), and for non-Indigenous women by 3.2% annually (ptrend<0.0001). Gestational diabetes prevalence increased significantly with age (p<0.0001), although the increase with age was significantly greater among Aboriginal women compared to non-Aboriginal women (pinteraction<0.0001), highlighting an important period for prevention. A meta-analysis of cross-sectional studies showed similar prevalence rates, with substantial heterogeneity (I²=97%), and subgroup analysis suggests this is most likely related to variation in screening and diagnostic practice. A retrospective data-linkage study was conducted evaluating postpartum screening for type 2 diabetes for all women giving birth at Cairns Hospital from 2004–2010 with gestational diabetes. Despite a significant increase over time from 2004–2010 (HR 1.15 per year, 95% CI 1.08-1.22, p<0.0001), rates of postpartum oral glucose tolerance testing (OGTT) remained low, with significantly lower rates among Aboriginal, compared to non-Aboriginal, women (10% vs 27%, respectively, by six months postpartum in 2010). Aboriginal women in Cairns had longer times to postpartum OGTT than Aboriginal women in remote areas, and non-Aboriginal women with proxy measures for lower socio-economic status had longer times to postpartum OGTT, than other non-Aboriginal women. The challenges posed by gestational diabetes are clearly not being met for Aboriginal women. Consultation with Aboriginal communities and evaluation of new initiatives is vital to mitigate the risks associated with an insufficient evidence-base. Comprehensive strategies are urgently needed to improve postpartum care after gestational diabetes and to utilise the ‘window of opportunity’ for diabetes prevention among Aboriginal women during the childbearing years.