Check Programme
The Hong Kong Practitioner VOLUME 24 / December 2002

Case one:

Scenario 4

Thus far Mary's pregnancy has progressed well. Her 12 week check was normal, her blood pressure has remained stable at 110-120/60-70 mmHg, her ultrasound has shown a normal sized and normally growing girl. She is now 26 weeks pregnant and is seeing you for her diabetes check.

HK Pract 2002;24:617-619

 

 
Question 1:

What should you arrange?

  1. A 2 hour 75g oral glucose tolerance test (OGTT with fasting and 2 hour venous plasma glucose tests)
  2. A 50g glucose challenge (at any time of the day and with a 1 hour venous plasma glucose test)
  3. Measurement of fasting plasma glucose
  4. Measurement of glycosylated haemoglobin (HbA1c).


Answer 1

2 is correct.

The recommended sequence (Figure 1) is a 50g* glucose challenge which does not require special arrangements for fasting or timing. If this is abnormal (1 hour value >7.8 mmol/L) a 75g OGTT is performed with appropriate preparation (3 days of carbohydrate intake exceeding 150g daily; fasting overnight apart from water). Gestational diabetes is diagnosed if fasting and 2 hour values exceed 5.5 and 8.0mmol/L respectively.

Fasting values are less sensitive and although HbA1c theoretically assesses the average blood glucose over a period of time, it has not been possible to establish diagnostic levels that are as sensitive and specific as the recommended test procedure.

* Generally the 50g challenge is preferred since it's the nationally recognised standard and it is associated with less side effects than the 75g challenge where the abnormal one hour level is 8.0mmol/L.



Figure 1: Recommended sequence for checking for and diagnosis of gestational diabetes (26-28 weeks)





Case two:

Scenario 5

All went well. Mary did have gestational diabetes and required insulin after 32 weeks to keep glucose levels within the recommended target (values before and after meals <5.5 and <7.0mmol/L respectively). Her delivery was uneventful apart from a small tear and Sally, her daughter, had an Apgar of 8. There were some problems establishing breast feeding but now Mary and John are very pleased with themselves and with Sally.

Mary is seeing you for her post natal check-up.

 
Question 2:

What advice should you give her about diabetes?

  1. She has twice the average risk of developing type 2 diabetes during her life (i.e. approximately 1 in 5)
  2. She should maintain the healthy lifestyle she established before becoming pregnant
  3. Sally is very likely to develop diabetes during childhood
  4. If her older sister (who also had irregular periods) plans a pregnancy, she should arrange the same diabetes checks as Mary did.


Answer 2

2 and 4 are correct.

Feedback

Mary has several risk factors and is very likely to develop type 2 diabetes in the future (Figure 2). In women with gestational diabetes alone the future risk is 40%-80% over the next 10 years and Mary has other risk factors.


Figure 2: Risk factors for diabetes

Best summed up as the 'Fs': Fat, fifty, family


There are no rigorous studies of interventions to prevent type 2 diabetes in women who have had gestational diabetes but it is generally agreed that maintaining healthy eating and activity schedules and healthy weight delays the onset. In any event Mary's daughter, Sally, is predisposed to type 2 diabetes and other components of Syndrome � and might benefit from growing up in an environment where a healthy lifestyle is encouraged and practised.

If Sally does develop diabetes it is likely to occur in adulthood (as for Mary) unless Sally becomes very overweight. As our population becomes fatter and less active many more young people are developing type 2 diabetes, especially in those groups with a strong genetic pre-disposition (e.g. Asian, Aboriginal, Maltese and Polynesian people).

Mary's sister (like Sally) shares half Mary's genes and probably has one of the indicators (polycystic ovary syndrome). She would be wise to follow the same plan as Mary: to establish a healthy lifestyle, to check for diabetes before stopping contraception and to check for gestational diabetes during the pregnancy.

 

 

Royal Australian College of General Practitioners