Glucose Tolerance Test in Pregnancy

Introduction

A glucose tolerance test (GTT) is a blood test to check if you have developed diabetes (high blood sugars) during your pregnancy. This is known as gestational diabetes mellitus and if left untreated, may lead to potential complications for both mother and baby. Testing is therefore important to identify and diagnose gestational diabetes mellitus.

The test is offered to:

1. Selected pregnant women at 26 weeks.*
2. All pregnant women at 16 weeks who developed gestational diabetes in a previous pregnancy. If the test result is normal at 16 weeks, it will be offered and repeated at 26 weeks gestation.
3. Any woman who develops potential signs of gestational diabetes in pregnancy – e.g. increased fluid around the baby or a large baby.

Preparation for the Glucose Tolerance Test

• The week before your test you should continue with your normal diet.
• From 9.30pm the night before your test, you can only have water – no other food or drink is allowed as this will cause the GTT result to be inaccurate.
• You may drink clear unflavoured water only.
• You must not have chewing gum or sweets while fasting before the test.

The Procedure

• The test will take approximately 2.5 hours.
• When you arrive a blood sample is taken from a vein in your arm. This is your fasting sample.
• You will then be given a measured glucose drink.
• Two hours later a further blood test will be collected from your arm.
• No food or drink (apart from water) is allowed until after the test is completed.
• You may drink clear water only.
• It is recommended you do not smoke during the test as this can affect the results.
• You will be required to stay at the hospital until the test is completed. You should rest quietly and not walk around or do any physical activity.
• Once the test is completed you can eat and drink normally. There is a tea bar opposite the clinic or alternatively please feel free to bring something to eat with you.
• There are no risks associated with this test.

The Results

If you have an abnormal test result, a midwife will telephone you to inform you of your abnormal results and when to expect an appointment to attend the Gestational Diabetes First Contact clinic. At this appointment you will be reviewed by the Specialist Diabetes Midwife, the Diabetes Specialist Dietician and a member of the Diabetes team who will provide you with and show you how to use a blood glucose meter.

If you are unable to attend the appointment or choose not to have the test, please telephone: The Administrative Team in the Women and Newborn Unit on 01274 364518 between 8.30am and 4.30pm Monday to Friday to rearrange or cancel the appointment.

People with hearing and speech difficulties, you can contact us using the Relay UK app. Textphone users will need to dial 18001 ahead of the number to be contacted.

*Selected pregnant women:

Women with any one of the following risk factors are offered GTT as per The National Institute for Health and Care Excellence (NICE) recommendations

1. Body mass index more than 30kg/m2
2. Previous baby weighing 4.5Kg or above
3. Previous diagnosis with gestational diabetes
4. First degree relative with diabetes
5. Ethnic minority - South Asian, Afro-Caribbean and middle eastern