Controversy over new criteria for gestational diabetes mellitus (GDM) has overshadowed the more serious adverse consequences of obesity on pregnancy outcomes, endocrinologists in NSW say.

In the first Australian study to compare the outcomes of GDM diagnosed by International Association of Diabetes Study Groups (IADPSG) and Australasian Diabetes in Pregnancy Society (ADIPS) 1998 criteria, clinicians at Westmead Hospital, Sydney, found that obesity was associated with a greater pregnancy risk than GDM diagnosed by the newly adopted criteria.

The study was done at a hospital that retained the ADIPS 1998 criteria but adopted  universal testing with OGTTs while allowing a comparison of the diagnosis of GDM by each criterion.

In a retrospective review of 6175 pregnancies, GDM was present in 15% by the ADIPS criteria and this would have increased to 17.8% with the IADPSG criteria.

Untreated women who had GDM according to IADPSG criteria had worse outcomes than the women who did not have GDM, but the criteria diagnosis was only an independent risk factor for induction of labour (Odds Ratio 1.41) and large for gestational age (OR 2.25).

In contrast, the potential impact of obesity in untreated women was much greater, as it was an independent risk factor for gestational hypertension (OR 5.32 vs normal weight), pre-eclampsia (OR 3.25), induction of labour (OR 1.86) small for gestational age (OR 1.61), shoulder dystocia (OR 1.91)  and primary caesarean section (OR 1.86).

The study authors, led by Dr Wah Cheung of the department of diabetes and endocrinology at Westmead Hospital, note that there is little evidence to show that glucose lowering treatment would have improved the outcomes of the women who were untreated due to use of the old ADIPS criteria.

They say the findings show it maybe more appropriate to invest stretched resources into the management of obesity in pregnancy, rather than the IADPSG only group.

“The management of obesity in pregnancy has attracted insufficient attention in Australia, with greater focus on glucose control. Perhaps this is because it is easier to treat hyperglycaemia,” they said.

“Obesity is associated with an even greater risk yet there are no standardised or systematic interventions for the management of obesity in pregnancy in Australia. A focus on healthy eating for appropriate weight gain in pregnancy is important to avoid both LGA and SGA. These issues should not be ignored in the glucocentric debate around the change in the diagnostic criteria for GDM.”

The findings are published in the Australia and NZ Journal of Gynaecology