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Gestational Diabetes Mellitus (GDM)

Gestational Diabetes Mellitus (GDM) - Diagnosis

Although the risk of GDM is higher in certain groups of women, it can happen to any woman in her pregnancy. In Singapore, all pregnant women will be offered screening for GDM with an oral glucose tolerance test (OGTT) between 24 and 28 weeks of pregnancy.

If you have had GDM before, have glucose in the urine or symptoms suggestive of diabetes, the OGTT will be performed earlier in pregnancy and repeated again at 24 to 28 weeks if the first test was normal.

Detection of GDM is important so that appropriate treatment can be given to reduce the risks to the pregnancy.

What is involved in an OGTT?

An OGTT to diagnose GDM requires:

  • Fasting overnight (not eating or drinking anything besides water)
  • Blood test for glucose in the morning, followed by a standard 75 g glucose drink
  • Repeat blood tests for glucose at 1 hour and 2 hours after the glucose drink

GDM is diagnosed if any one of the three blood results indicate a higher than expected blood glucose level.

Are there any risks or side effects from the OGTT?

The standard glucose drink is sweet and may cause some to feel nauseated. In rare cases, it may trigger vomiting. If this happens, the test will need to be rescheduled to another day if you are agreeable.

Why should I do the OGTT?

All pregnant women are strongly encouraged to undergo the test as GDM is a common condition in pregnancy, and there are potential risks to the pregnancy if it is not detected and treated promptly.

Should you decline to do the test, please help us understand your reasons for not wanting to do so. We would like to reassure you that your decision, whatever it may be, will not affect your subsequent antenatal care.

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