Data gaps

A number of data gaps have been identified for the comprehensive reporting on gestational diabetes. 

Reporting recurrence

Gestational diabetes usually resolves after the baby is born, however women who have had a pregnancy complicated by gestational diabetes have a significantly increased risk for the recurrence of the condition in later pregnancies. Studies have shown recurrence rates to vary between 30% and 84% (Kim et al. 2007) with the risk of recurrence increasing with the number of pregnancies and among higher risk ethnic groups (Non-Hispanic black, Hispanic and Asian/Pacific Islander) (Schwartz et al. 2015).

Reporting on the recurrence of gestational diabetes is not possible using the National Hospital Morbidity Database (NHMD)—the primary data source for this web report, as the NHMD provides information on de-identified episodes of care that cannot be linked across multiple admissions.

The National Diabetes Services Scheme (NDSS) is an Australian Government subsidy scheme which has been administered by Diabetes Australia for the Australian Government since 1987. By registering with the NDSS, people with diabetes are provided with subsidised diabetes-related products, information and support. The NDSS captures people with type 1, type 2, gestational and other forms of diabetes.

Data Snapshots from the NDSS currently provide an indication of the number of NDSS registrations for repeat gestational diabetes diagnoses within a 12-month period, dating back to 2014.

Reporting pre-existing diabetes in pregnancy

There are currently limitations to national reporting on outcomes of mothers who have pre-existing diabetes and their babies. Further, it is not always possible to decipher from the data if the diabetes is pre-existing or gestational. It is an important subgroup with the AIHW’s Diabetes in pregnancy 2014–2015 report finding that compared with mothers with no diabetes in pregnancy, mothers with pre-existing type 1 and type 2 diabetes and gestational diabetes had higher rates of caesarean section, induced labour, pre-existing and gestational hypertension, and pre-eclampsia. They also had longer antenatal and postnatal stay in hospital (5 or more days). Compared with babies of mothers with gestational diabetes or no diabetes, babies of mothers with pre-existing diabetes had higher rates of pre-term birth, stillbirth, low and high birthweight, low Apgar score, resuscitation, and special care nursery/neonatal intensive care unit admission, and stayed longer in hospital (AIHW 2019).

The NPDC is a national population-based cross-sectional collection of data on pregnancy and childbirth and contains information about the diabetes status of women who gave birth. While it is a useful data source, the current information on maternal diabetes that it contains has several limitations, including the inability of some states and territories to distinguish between pre-existing types of diabetes, and differences in data collection methods across jurisdictions. Data on diabetes status in Victoria are not collected in a format comparable with the specification for the NPDC and were excluded in the report when reporting on gestational diabetes and pre-existing diabetes.

The NHMD provides national data on pregnancies affected by diabetes, but ICD-10-AM coding changes and the accuracy of recording diabetes type affects the ability to report on the number of pregnancies affected by, and complications from pre-existing diabetes type.

Reporting longer-term complications

Longer-term health complications associated with gestational diabetes for the mother include a significantly increased risk for the development of type 2 diabetes, metabolic syndrome and cardiovascular disease. Babies of mothers with gestational diabetes are also at an increased risk of type 2 diabetes, metabolic syndrome and obesity in later life (Kampmann et al. 2015).

The NHMD allows the reporting of short-term outcomes for the mother, relating to pregnancy and the birth event. However, as records in the NHMD are for individual episodes of care, longer-term complications cannot be reported.

Babies affected by maternal diabetes can be identified through the NHMD with ICD-10-AM Chapter XVI P70 codes. Using the P70 codes and any additional diagnoses reported on the records of the babies, will provide information on the impact of maternal diabetes on babies. However, the codes are not able to comprehensively identify all babies born to mothers with diabetes, as they only identify babies affected by maternal diabetes, and not all babies born to a mother with diabetes will experience complications.

The NPDC contains information about the diabetes status of women who gave birth, and associated adverse maternal and perinatal outcomes around the time of birth. However, the NPDC does not collect information to assess longer-term health implications for the mother and baby. Reporting of some pregnancy-related outcomes—such as eclampsia, antepartum haemorrhage, postpartum haemorrhage, and complications of the puerperium—is also voluntary, and might not be provided by all jurisdictions.

Linkage of maternal records with other data sources would be required in order to accurately report, at a national level, on the recurrence of gestational diabetes, identifying women with pre-existing and other diabetes types and to report longer-term complications from gestational diabetes, both for the mother and the baby.

For further information, refer to the AIHW’s Improving national reporting on diabetes in pregnancy: technical report.

References

AIHW (Australian Institute of Health and Welfare) 2019. Diabetes in pregnancy 2014–2015. Bulletin no. 146. Cat. no. CDK 7. Canberra: AIHW.

Kampmann U, Madsen LR, Skajaa GO, Iversen DS, Moeller N & Ovesen P 2015. Gestational diabetes: a clinical update. World Journal of Diabetes 6:1065–72.

Kim C, Berger DK & Chamany S 2007. Recurrence of Gestational Diabetes Mellitus: a systematic review. Diabetes Care 30(5):1314–1319. 

Schwartz N, Nachum Z & Green MS 2015. The prevalence of gestational diabetes mellitus recurrence—effect of ethnicity and parity: a meta analysis. American Journal of Obstetrics & Gynecology 213(3):310–317. doi:10.1016/j.ajog.2015.03.01.