Much of the recent debate around the world regarding gestational diabetes has concerned its diagnosis. In the past traditional methods of diabetes diagnosis such as using a standard glucose tolerance test as recommended by the WHO has also applied to diagnosing gestational diabetes. It has become routine in many clinics across the globe to recommend such a test to pregnant women, and particularly those considered high risk, at about 24 to 28 weeks of pregnancy.
A positive diagnosis of so called gestational diabetes requires assessment, monitoring and treatment in much the same way as in pregnant women with Type 2 diabetes so as to avoid the well known diabetes related adverse pregnancy outcomes. Which treatment to use remains controversial, as after a dietary approach insulin has been considered gold standard. However more recent reviews have demonstrated that there are no substantial maternal or neonatal differences when glyberide or Metformin is used compared to insulin in women with gestational diabetes.
This whole approach to diagnosing gestational diabetes has been thrown into doubt by new emerging data which demonstrates how even mild abnormalities of blood glucose control cause these very same adverse pregnancy outcomes albeit at lesser frequency. The publication of Hyperglycaemia and Adverse Pregnancy Outcome Study, the so called HAPO study, showed how subtle variations of maternal glucose levels below those diagnostic for diabetes influence foetal size and pregnancy outcomes.
As a result of this large scale and extremely well designed multi-centre research programme many countries are now adopting a stricter policy of diagnostic criteria for gestational diabetes. Although the aim is to positively influence foetal growth and pregnancy outcomes it must also be born in mind that we might also be considered by some to ‘medicalise’ what was previously thought of as normal.
The new diagnostic criteria are quite tight, requiring only one of the following to diagnose gestational diabetes after a 75g glucose tolerance test:
- A fasting glucose of 5.1 mmol/l
- A one hour post prandial of 10.0 mmol/l
- Or a two hour post prandial of 8.5 mmol/l
The practical considerations involved in managing a vastly increased population of patients with gestational diabetes will also have to be thought through. There will be cost and resource implications and many instances where these will probably not be met.
My conclusion is that this study has opened up a huge area of scientific interest, an area of medicine where environmental factors influences genetics and development.
It is not only fascinating but it is also relevant to all of us as clinicians. The focus on nutrition and metabolism in pregnancy will be of interest to most women seeking advice during pregnancy even if the logistics of rolling out a community programme of diagnosis and management proves taxing.