Volume 179 - Issue 2
Gestational diabetes in Victoria in 1996: incidence, risk factors and outcomes
Authors: Christine A Stone, Kylie A McLachlan, Jane L Halliday, Peter Wein and Christine Tippett
Med J Aust 2003; 179 (2): 118-119. || doi: 10.5694/j.1326-5377.2003.tb05457.x
Published online: 21 July 2003
Published online: 21 July 2003
Christine A Stone,* Kylie A McLachlan,† Jane L Halliday,‡ Peter Wein,§ Christine Tippett¶
* Epidemiologist, Prevention and National Health Priorities, ‡ Epidemiologist, Birth Defect Registry, Perinatal Data Collection Unit, Public Health Division, Department of Human Services, 17th Floor, 120 Spencer Street, Melbourne, VIC 3001; † Research Fellow in Endocrinology, Department of Endocrinology and Diabetes, St Vincent's Hospital, Fitzroy, VIC; § Senior Lecturer, Department of Obstetrics and Gynaecology, University of Melbourne, East Melbourne, VIC; ¶ Director, Maternal Fetal Medicine, Monash Medical Centre, Clayton, VIC. christine.stoneATdhs.vic.gov.au
In reply: We thank Davey for his comments, which provide us with the opportunity to highlight the benefits and limitations of reports using population-based data. The value of population-based data is that the reported incidence, risk factors and outcomes reflect current practice in the whole of Victoria and are not subject to bias introduced by local referral patterns or clinical practice. Our study1 shows that, in addition to established risk factors for gestational diabetes mellitus (GDM), the reported incidence varies according to hospital size and geographic location, demonstrating the type of bias that can occur. In addition, the large number of subjects in our study (over 60 000) enables more accurate analysis of subgroups.
A limitation, already highlighted in our discussion, is that we are restricted to the parameters available within the data sources used. Davey and Hamblin's article2 demonstrates the difficulty of obtaining individual patient data on body mass index, racial grouping, and family history of diabetes. Even working at the hospital level, they had to extrapolate from population-level data to derive an estimate of these risk factors among the control subjects.2 Given that their study population is a subgroup of ours,1 it is no surprise that the two studies showed similar results.
An important implication for providers of health services is that, with increases in the age at which mothers give birth and in the number of births to Asian-born mothers,3 we predict that the prevalence of GDM in Victoria will rise.
Davey correctly points out that our article does not refer to a relevant 1997 study by the Toronto group.4 However, we do actually refer to a later publication by the same group.5
The problem of ethnicity and migration arises in studies of conditions that are not only polygenic but also a result of complex interactions between a person's genes and his or her environment.
Lastly, the source of information on macrosomia was 1996 population data. We have since produced a percentile chart of weight (g) for gestational age (weeks) based on 15 years of Victorian data.6
References
- Stone CA, McLachlan KA, Halliday JL, et al. Gestational diabetes in Victoria in 1996: incidence, risk factors and outcomes. Med J Aust 2002; 177: 486-491. <eMJA full text>
- Davey RX, Hamblin PS. Selective versus universal screening for gestational diabetes mellitus: an evaluation of predictive risk factors. Med J Aust 2001; 174: 118-121.
- Riley M, Halliday J. Births in Victoria 1999-2000. Melbourne: Perinatal Data Collection Unit, Victorian Government Department of Human Services, 2001.
- Naylor CD, Sermer M, Chen E, Farine D. Selective screening for gestational diabetes mellitus. Toronto Trihospital Gestational Diabetes Project Investigators. N Engl J Med 1997; 337: 1594-1596.
- Sermer M, Naylor CD, Farine D, et al. The Toronto Tri-Hospital Gestational Diabetes Project. A preliminary review. Diabetes Care 1998; 21 Suppl 2: B33-B42.
- Halliday J, Ellis I, Stone C. WUDWAW: "Who usually delivers whom and where". Report on models of antenatal care. Melbourne: Perinatal Data Collection Unit, Department of Human Services, 1999.