Gestational diabetes (diabetes in pregnancy)

Expert reviewer, Dr Jonathan Katz, Consultant Endocrinologist
Next review due June 2021

Gestational diabetes is a type of diabetes that you may develop when you’re pregnant and your blood glucose (sugar) level is too high. It’s also known as gestational diabetes mellitus (GDM). It can cause problems for both you and your baby if you don’t control it. But there are treatments, as well as changes you can make to your lifestyle that can help to reduce its impact on your pregnancy.

About gestational diabetes

Your body produces a hormone (chemical) called insulin to control the glucose level in your blood. When you’re pregnant, your hormones, such as oestrogen and progesterone cause your cells to become less sensitive to insulin.

In response, your body needs to produce more insulin than usual to help control the high level of glucose in your blood. If you develop gestational diabetes, your body either doesn’t release enough insulin, or your cells don’t respond to it. The result is that your blood glucose level remains high. This can have a number of effects on you and your baby.

Symptoms of gestational diabetes

You probably won’t notice any symptoms of gestational diabetes because it’s usually diagnosed in a routine screening test before any develop. But if it isn’t picked up in tests, you may develop symptoms. For example, you may:

  • feel thirsty and drink more than usual
  • go to the toilet more often (to wee)
  • feel extremely tired

These symptoms can be quite common if you’re pregnant so they aren’t always caused by gestational diabetes. But if you have them, tell your midwife or GP.

Diagnosis of gestational diabetes

At your first antenatal appointment, your midwife will ask you some questions to assess your risk of gestational diabetes. Based on your answers, you may be offered a test to find out if you’ve developed it. Your midwife will usually offer you the test when you’re between 24 and 28 weeks pregnant. But you might need to have it earlier if you’ve had gestational diabetes before.

The test for gestational diabetes is called an oral glucose tolerance test, and it takes about two hours. You can’t eat anything for about eight to 12 hours before the test so your clinic may try to arrange a morning appointment. Your nurse or health professional will take a sample of your blood and then give you a glucose drink. You’ll need to rest for a couple of hours, then they’ll take another blood sample to see how your body is dealing with the glucose. They’ll measure how much glucose is in your blood to find out.

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Treatment of gestational diabetes

If you’re diagnosed with gestational diabetes, your midwife or GP will refer you to a joint diabetes and antenatal clinic. The doctors, nurses, midwives and other health professionals in the team have plenty of experience looking after pregnant women with diabetes. They’ll keep an eye of you throughout your pregnancy, so you’ll have more antenatal appointments than women who don't have gestational diabetes.

Your treatment will aim to keep your blood glucose low enough to help prevent complications. You’ll need to test your blood regularly to check this.

Monitoring your blood glucose level

To test your blood glucose, you’ll need to take a pinprick of blood from the side of your fingertip and put a drop on a testing strip. You might find it helps to wash and dry your hands in warm water beforehand so your blood flows more freely. You place the testing strip into a glucose meter, which reads it and shows you the result automatically. Your specialist diabetes nurse will give you advice on how to test your blood glucose level, how often, and the level that you're aiming for.


Your doctor or specialist nurse will give you some advice on ways to manage gestational diabetes by making changes to your lifestyle. Your GP may refer you to a dietitian, who can advise you about keeping your blood glucose level under control. This may involve making changes to your diet and how much exercise you do. This may be all you need to do to keep your blood glucose level low enough to help reduce the risk of complications.

It’s important to eat a healthy balanced diet to help to keep your blood glucose level stable and within the ideal range. Include carbohydrates that release energy slowly. See our infographic on the glycaemic index below for more information.

It’s important to keep active when you’re pregnant too – this can reduce your risk of developing gestational diabetes in the first place. Speak to your doctor or midwife if you have any concerns about exercising during pregnancy, or if you haven’t previously been doing any exercise.

For more information about what to eat and how to get more active, see Related information.


If you’ve tried to control diabetes by making lifestyle changes but, after two weeks, it hasn’t made any difference, you may need to take medicines. Your doctor will talk to you about the different options available.


Your doctor may prescribe you insulin, which you will need to take as an injection. They’ll show you how to inject yourself and give you advice on when to do this.

If injections of insulin don’t work out for you, your doctor may suggest you use a portable insulin pump. These are devices that are attached to your body and deliver insulin through a small tube called a cannula that lies just under your skin. They deliver a regular, or constant amount of insulin into your body. You may find these easier if you need to have several injections a day, or if you find it difficult to control your blood glucose with regular injections.

Other medicines

Some of the tablets that are used to treat type 1 and type 2 diabetes aren’t recommended for pregnant women. But depending on your circumstances, your doctor may prescribe you medicines called metformin or glibenclamide. These work in different ways to reduce the level of glucose in your blood.

Glycaemic index

You can help to control your blood glucose level by making some changes to your diet. Aim to eat more high-fibre, low-glycaemic index sources of carbohydrate and low-fat protein foods. An explanation of the glycaemic index and examples of low GI foods is given below.

Click to open a PDF version of Bupa's Glycaemic index (0.6MB)


Causes of gestational diabetes

There are a number of things that can increase your risk of developing gestational diabetes. You’re more at risk if you:

  • are older (over 40)
  • smoke
  • are overweight or obese
  • don’t exercise regularly
  • have previously given birth to a large baby who weighed 4.5kg (10 pounds) or more at birth
  • have had gestational diabetes before
  • have a close relative with diabetes, such as a parent, brother or sister
  • have polycystic ovary syndrome
  • eat a diet that’s low in fibre, and a high glycaemic index value (for information about the glycaemic index, see our infographic above, and the topic: Carbohydrates)

Gestational diabetes is also more common in people with a South Asian, African-Caribbean or Middle Eastern background.

Complications of gestational diabetes

Complications affecting you

Complications of gestational diabetes that can affect you include the following.

  • Pre-eclampsia, which is when you develop high blood pressure during your pregnancy.
  • Polyhydramnios, which is when you have too much amniotic fluid (the fluid around your baby in your womb). It can increase your risk of premature labour. It could also be a sign that your baby is in the wrong position for birth.
  • Difficulties giving birth naturally – you might need to have a caesarean. Your baby may grow larger than normal if you have diabetes while you’re pregnant. Your midwife will check the size of your baby throughout your pregnancy. You might need to be induced, which means your doctor will start your labour using medicines. They’ll go through your options with you.

A complication of treatment for gestational diabetes is hypoglycaemia, which is when you’re blood glucose level becomes too low. For more information, see our FAQ: What is hypoglycaemia? below.

There are two future risks that might affect you too.

  • You're more likely to develop gestational diabetes if you have another baby.
  • You have a higher risk of developing type 2 diabetes later in life. After you’ve had your baby, you’ll need to be checked for type 2 diabetes regularly so that you get any treatment you need.

Complications affecting your baby

Complications that may affect your baby include the following.

  • Your baby may grow larger than normal. This can make labour and giving birth more difficult, and can increase the risk of shoulder dystocia (where your baby’s shoulders get stuck during birth). Your midwife or doctor will advise you on the best way to give birth to your baby safely.
  • Your baby may have low blood glucose (hypoglycaemia) after they’re born. This will be monitored, and your baby will only need to have treatment if their blood glucose drops below a certain level.
  • Your baby has a higher risk of developing jaundice. This can cause your baby’s skin and eyes to have a yellow tinge.
  • If born premature, there’s a higher chance of your baby having breathing difficulties. This can happen if your baby’s lungs haven’t fully developed when you give birth, and will need treatment.
  • There’s a greater chance of stillbirth if you have gestational diabetes. You’ll be monitored throughout your pregnancy to help prevent this, as well as other complications.

Gestational diabetes after your baby is born

Your healthcare team will test both you and your baby’s blood glucose levels shortly after you give birth, to make sure they’re in the normal range. Doctors recommend you breastfeed your baby straightaway to keep their blood glucose at a safe level.

For most women, once they have their baby, gestational diabetes goes away. So you can usually stop taking medicines for gestational diabetes as soon as you give birth. You’ll need to have a blood glucose test at your six-week check-up to ensure that your blood glucose has returned to normal.

It’s important to keep your blood glucose level under control and carry on with any changes you’ve made to your lifestyle. This is because you have a greater risk of developing type 2 diabetes once you’ve had gestational diabetes. Make sure that you make an appointment to get your blood glucose checked once a year.

There’s a chance that your blood glucose level could remain high after you’ve given birth. This means you could develop diabetes, even though you’re no longer pregnant. About half of women with gestational diabetes will go on to develop type 2 diabetes within 10 years. You can reduce your risk by improving your lifestyle; for example, by being active, eating a balanced diet and maintaining a healthy weight. Your doctor will talk to you about some options to manage the condition.

Frequently asked questions

  • If your diabetes is well controlled, it shouldn’t affect how you have your baby. But if it isn’t, for a number of reasons, you may need to have a caesarean delivery.

    If you have gestational diabetes and haven’t had your baby by 40 weeks, you’ll usually have your labour induced or have a caesarean. Being induced means your labour is started by your doctor, before your due date.

    You can discuss your options at your antenatal appointments. Your doctor will usually advise you to have your baby in a hospital that has a team experienced in looking after women who have diabetes. Home births aren’t usually a recommended option for women who have gestational diabetes because of the risks to you and your baby.

    Your blood glucose level will be checked throughout your labour. You may need an intravenous drip (a tube put into a vein in your arm) during labour. This is so you can be given insulin and glucose solution to ensure your blood glucose level remains within the correct range.

    Your doctor will talk through your options with you and help you prepare for giving birth. Your baby will be continuously monitored throughout your labour to make sure they’re safe.

  • Hypoglycaemia (or a ‘hypo’) is when you have very low levels of blood glucose. Your doctor or specialist nurse will explain how to recognise the symptoms of this, and what to do if it happens.

    You can get hypoglycaemia if you take too much of your medicines for gestational diabetes, or miss a meal after taking your medicines. Most people get warning signs before hypoglycaemia. You might:

    • feel hungry
    • feel your heart pounding
    • feel shaky and nervous
    • sweat a lot
    • feel irritable
    • feel confused
    • have blurred vision
    • get tingling lips

    Your doctor or specialist nurse will explain how to recognise these symptoms and what to do. For example, it’s a good idea to keep a sugary, soft drink with you at all times.

  • If you develop gestational diabetes, it’s possible that you might get it again if you have another baby. This happens to around half of women.

    There are some things that can make this more likely to happen, which include:

    • getting older – the older you are, the higher your risk
    • a higher body mass index (BMI) than normal
    • putting on weight between your pregnancies

    There are things you can do to help prevent this happening. For example, you can aim to have a healthy lifestyle between pregnancies by eating a healthy diet and doing plenty of exercise. Try to stick to a healthy weight too. For advice about how to do this, see Related information.

    Let your doctor or midwife know at your first antenatal appointment that you’ve had gestational diabetes before. They can then make sure you get the right help and support.

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  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, June 2018
    Expert reviewer, Dr Jonathan Katz, Consultant Endocrinologist
    Next review due June 2021