Gestational Diabetes

This leaflet explains what gestational diabetes is. It also explains why it develops and how it is diagnosed.


 This is a type of diabetes that affects pregnant women, usually during the second or third trimester. In the vast majority of cases gestational diabetes disappears after the baby is born.  Gestational diabetes is more common in women who are overweight but may develop in other situations. These include;

  • Gestational Diabetes in a previous pregnancy
  • A large baby in a previous pregnancy (over 10lb)
  • An unexplained stillbirth
  • Being over 25 year’s old
  • Family history of diabetes
  • Previous difficult pregnancy and/or delivery

Why does gestational diabetes develop?

Insulin is produced by the body and keeps blood sugar (glucose) levels under control.  During pregnancy, the body produces hormones (chemicals) that work against insulin; this means that more insulin is needed to keep the blood glucose normal.  If not enough insulin is produced to do this, blood sugar rises and diabetes develops. When the blood sugar is sufficiently high, glucose can pass through to the kidneys and into the urine.

How is gestational diabetes diagnosed? 

At the booking visit around 12 week’s gestation all women should be assessed for the presence of risk factors for gestational diabetes. If risk factors present a glucose tolerance test is usually carried out between 26 – 28 weeks of gestation. A further blood test for sugar is also set at around the 24th – 28th weeks of pregnancy. If the sugar level is high a Glucose Tolerance Test is carried out.


If blood tests are diagnostic of gestational diabetes women should be offered a review with the joint diabetes and antenatal clinic within 1 week.

What treatment is needed?

High blood sugar levels in the mother pass to the baby. This causes the baby to grow very large and can lead to a difficult labour. Keeping your blood sugar under control will help to avoid this. If you smoke, you must stop immediately.

The amount and the type of food that you eat affect your blood sugar levels.

The dietitian will advise you about healthy eating.

Healthy Eating

  • Eat regularly, 3 meals a day
  • Avoid sweet and sugary foods
  • Eat more high fibre foods, and limit starchy foods focusing on low glycaemic index foods
  • Cut down on fatty foods
  • Eat plenty of vegetables and have fruits in moderation, spread out through the day. 

The Diabetes Specialist Nurse will show you how to test your blood sugar at home. You will be asked to do this regularly. Occasionally healthy eating on its own may not be sufficient to keep the blood sugar under control and tablets or insulin injections may be necessary. If this happens to you, the Diabetes team will be there to give you all the help you need. 

Other useful information

When you have Gestational Diabetes, you need regular assessment at the ante-natal clinic. A team of doctors and nurses specialising in both pregnancy and diabetes will look after you. You will also see a specialist dietitian. They will be interested in how well your baby is developing and how well controlled your blood sugar is. This will help to determine when and how your baby will be delivered. The aim will be for you to have a normal delivery, but most likely your baby should be born in hospital. You will be able to breastfeed your baby if you wish.

Post Delivery 

 In most women, this type of diabetes disappears after the baby is born.

All women with Gestational Diabetes should have a fasting glucose and Hba1c test (a blood test which is an indicator of the glucose levels over the preceding 3 months) 3 months after their baby is born to make sure that the diabetes has gone. There is a chance that diabetes could return with another pregnancy or with getting older.

It is advisable to have your blood sugar checked once a year, for life, to make sure that diabetes has not developed silently.

To avoid developing diabetes in the future

  • Keep to a healthy diet
  • Take regular exercise
  • Keep your weight down to the ideal weight for your height

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