Diabetes, gestational
Diabetes, gestational

Gestational diabetes is high blood sugar that develops during pregnancy and usually disappears after giving birth.

It can occur at any stage of pregnancy, but is more common in the second half.

It occurs if your body cannot produce enough insulin – a hormone that helps control blood sugar levels – to meet the extra needs in pregnancy.

Gestational diabetes can cause problems for you and your baby during and after birth. But the risk of these problems happening can be reduced if it's detected and well managed.

Who's at risk of gestational diabetes

Any woman can develop gestational diabetes during pregnancy, but you're at an increased risk if:

  • your body mass index (BMI) is above 30 – use the healthy weight calculator to work out your BMI
  • you previously had a baby who weighed 4.5kg (10lbs) or more at birth
  • you had gestational diabetes in a previous pregnancy
  • one of your parents or siblings has diabetes
  • your family origins are south Asian, Chinese, African-Caribbean or Middle Eastern (even if you were born in the UK)

If any of these apply to you, you should be offered screening for gestational diabetes during your pregnancy.

Symptoms of gestational diabetes

Gestational diabetes doesn't usually cause any symptoms.

Most cases are only picked up when your blood sugar level is tested during screening for gestational diabetes.

Some women may develop symptoms if their blood sugar level gets too high (hyperglycaemia), such as:

  • increased thirst
  • needing to pee more often than usual
  • a dry mouth
  • tiredness

But some of these symptoms are common during pregnancy anyway and aren't necessarily a sign of a problem. Speak to your midwife or doctor if you're worried about any symptoms you're experiencing.

How gestational diabetes can affect your pregnancy

Most women with gestational diabetes have otherwise normal pregnancies with healthy babies.

However, gestational diabetes can cause problems such as:

  • your baby growing larger than usual – this may lead to difficulties during the delivery and increases the likelihood of needing induced labour or a caesarean section
  • polyhydramnios – too much amniotic fluid (the fluid that surrounds the baby) in the womb, which can cause premature labour or problems at delivery
  • premature birth – giving birth before the 37th week of pregnancy
  • pre-eclampsia – a condition that causes high blood pressure during pregnancy and can lead to pregnancy complications if not treated
  • your baby developing low blood sugar or yellowing of the skin and eyes (jaundice) after he or she is born, which may require treatment in hospital
  • the loss of your baby (stillbirth) – though this is rare

Having gestational diabetes also means you're at an increased risk of developing type 2 diabetes in the future.

Screening for gestational diabetes

During your first antenatal appointment at around weeks 8 to 12 of your pregnancy, your midwife or doctor will ask you some questions to determine whether you're at an increased risk of gestational diabetes.

If you have one or more risk factors for gestational diabetes – see Who's at risk, above – you should be offered a screening test.

The screening test used is called an oral glucose tolerance test (OGTT), which takes about two hours.

It involves having a blood test taken in the morning when you've had nothing to eat or drink (except water) overnight. You're then given a glucose drink.

After resting for two hours, another blood sample is taken to see how your body is dealing with the glucose.

The OGTT is done when you're between 24 and 28 weeks pregnant. If you've had gestational diabetes before, you'll be offered an OGTT earlier in pregnancy soon after your booking visit, and another OGTT at 24 to 28 weeks if the first test is normal.

Treatments for gestational diabetes

If you have gestational diabetes, the chances of having problems with the pregnancy can be reduced by controlling blood sugar levels.

You'll be given a blood sugar testing kit so you can monitor the effects of treatment.

Blood sugar levels can be reduced by changes in diet and exercise.  But the majority of women will need medication as well if changes in diet and exercise don't reduce blood sugar enough. This may be tablets or insulin injections.

You'll also be more closely monitored during your pregnancy and birth to check for any potential problems.

If you have gestational diabetes, it's best to give birth before 41 weeks. Induction of labour or a caesarean section may be recommended if labour doesn't start naturally by this time.

Earlier delivery may be recommended if there are concerns about your or your baby's health or if your blood sugar levels haven't been well controlled.

Read more about how gestational diabetes is treated.

Long-term effects of gestational diabetes

Gestational diabetes normally goes away after birth. But women who've had it are more likely to develop:

  • gestational diabetes again in future pregnancies
  • type 2 diabetes – a lifelong type of diabetes

You should have a blood test to check for diabetes 6 to 13 weeks after giving birth, and every year thereafter if the result is normal.

See your GP if you develop symptoms of high blood sugar, such as increased thirst, needing to pee more often than usual, and a dry mouth – don't wait until your next test.

You should have the tests even if you feel well, as many people with diabetes don't have any symptoms.

You'll also be advised about things you can do to reduce your risk of developing diabetes, such as maintaining a healthy weight, eating a balanced diet and exercising regularly.

Some research has suggested that babies of mothers who had gestational diabetes may be more likely to develop diabetes or become obese later in life.

Planning future pregnancies

If you've had gestational diabetes before and you're planning to get pregnant, make sure you get checked for diabetes. Your GP can arrange this.

If you do have diabetes, you should be referred to a diabetes pre-conception clinic for support to ensure your condition is well controlled before you get pregnant.

Read more about diabetes in pregnancy.

If you have an unplanned pregnancy, talk to your GP and tell them you had gestational diabetes in your previous pregnancy.  

If tests show you don't have diabetes, you'll be offered screening earlier in pregnancy soon after your booking visit, and a repeat screening test at 24 to 28 weeks if the first test is normal.

Alternatively, it may be suggested that you start testing your blood glucose yourself using a finger-pricking device in the same way as you did during your previous gestational diabetes.

^^ Back to top


If you have gestational diabetes, the chances of having problems with the pregnancy can be reduced by controlling your blood sugar (glucose) levels.

You'll also need to be more closely monitored during pregnancy and labour to check if treatment is working and to check for any problems.

This section covers:

Checking your blood sugar level

You'll be given a testing kit that you can use to check your blood sugar level.

This involves using a finger-pricking device and putting a drop of blood on a testing strip.

You'll be advised:

  • how to test your blood sugar level correctly
  • when and how often to test your blood sugar – most women with gestational diabetes are advised to test before breakfast and one hour after each meal
  • what level you should be aiming for – this will be a measurement given in millimoles of glucose per litre of blood (mmol/l)

Diabetes UK has more information about monitoring your glucose levels.


Making changes to your diet can help control your blood sugar level.

You should be offered a referral to a dietitian, who can give you advice about your diet, and you may be given a leaflet to help you plan your meals.

You may be advised to:

  • eat regularly – usually three meals a day – and avoid skipping meals
  • eat starchy and low glycaemic index (GI) foods that release sugar slowly – such as wholewheat pasta, brown rice, granary bread, all-bran cereals, pulses, beans, lentils, muesli and porridge
  • eat plenty of fruit and vegetables – aim for at least five portions a day
  • avoid sugary foods – you don't need a completely sugar-free diet, but try to swap snacks such as cakes and biscuits for healthier alternatives such as fruit, nuts and seeds
  • avoid sugary drinks – sugar-free or diet drinks are better than sugary versions; be aware that fruit juices and smoothies contain sugar, too, and so do some "no added sugar" drinks, so ensure you check the label or ask your health care team
  • include lean – not fatty – sources of protein in your diet, such as fish

It's also important to be aware of foods all pregnant women should avoid, such as certain types of fish and cheese.

Diabetes UK has more information about diet and lifestyle with gestational diabetes.


Physical activity lowers your blood glucose level, so regular exercise can be an effective way to manage gestational diabetes.

You'll be advised about safe ways to exercise during pregnancy. Read about exercise in pregnancy for more information.

A common recommendation is to aim for at least 150 minutes (2 hours and 30 minutes) of moderate intensity activity a week.

This is any activity that raises your heart rate and makes you breathe faster, such as brisk walking or swimming.


You may be offered medication if your blood sugar level is not under control a week or two after changing your diet and exercising regularly, or if your blood sugar is very high. This may be tablets – usually metformin – or insulin injections.

Your blood sugar level can increase as your pregnancy progresses, so even if your blood glucose levels are well controlled at first, you may need to take medication later in pregnancy.

These medications will be stopped after you give birth.


Metformin is taken as a tablet up to three times a day, usually with or after meals.

Side effects of metformin can include:

  • feeling sick
  • vomiting
  • stomach cramps
  • diarrhoea
  • loss of appetite

Occasionally a different tablet called glibenclamide may be used.

Insulin injections

Insulin may be recommended if:

  • you can't take metformin or it causes side effects
  • your blood sugar level isn't controlled with metformin
  • you have very high blood sugar
  • your baby is very large or you have too much fluid in your womb (polyhydramnios)

Insulin is taken as an injection, which you'll be shown how to do yourself. Depending on the type of insulin you're prescribed, you may need to inject yourself before meals, at bedtime, or on waking.

You will be told how much insulin to take. Blood sugar levels usually increase as pregnancy progresses, so your insulin dose may need to be increased over time.

Insulin can cause your blood sugar to fall too low (hypoglycaemia). Symptoms of low blood sugar include feeling shaky, sweaty, hungry, turning pale, or finding it difficult to concentrate.

If this happens, you should test your blood sugar – treat it straight away if it's low. Find out how to treat low blood sugar.

You'll be given information about hypoglycaemia if you're started on insulin.

Monitoring your pregnancy

Gestational diabetes can increase the risk of your baby developing problems, such as growing larger than usual.

Because of this, you'll be offered extra antenatal appointments so your baby can be closely monitored.

Appointments you should be offered include:

  • an ultrasound scan at around weeks 18-20 of your pregnancy – to check your baby for abnormalities
  • ultrasound scans at weeks 28, 32 and 36 – to monitor your baby's growth and the amount of amniotic fluid, and regular checks from week 38

Giving birth

The ideal time to give birth if you have gestational diabetes is usually around weeks 38 to 40.

If your blood sugar is within normal levels and there are no concerns about your or your baby's health, you may be able to wait for labour to start naturally.

But you'll usually be offered induction of labour or a caesarean section if you haven't given birth by 40 weeks and 6 days.

Earlier delivery may be recommended if there are concerns about your or your baby's health, or if your blood sugar levels haven't been well controlled.

You should give birth at a hospital where health care professionals are available to provide appropriate care for your baby 24 hours a day.

When you go into hospital to give birth, bring your blood sugar testing kit and any medications you're taking with you.

Usually you should keep testing your blood sugar and taking your medications until you're in established labour or you're told to stop eating before a caesarean section.

During labour and the birth, your blood glucose will be monitored and kept under control. Some women may need a drip of insulin to control their blood sugar levels.

After birth

You can usually see, hold and feed your baby soon after you've given birth. It's important to feed your baby as soon as possible after birth (within 30 minutes) and then at frequent intervals (every 2-3 hours) until your baby's blood sugars are stable.

Your baby's blood sugar level will be tested starting two to four hours after birth. If it's low, your baby may need to be temporarily fed through a tube or a drip.

If your baby is unwell or needs close monitoring, they may be looked after in a specialist neonatal unit.

Any medication you were on to control your blood sugar will usually be stopped when you give birth. You'll usually be advised to keep checking your blood sugar for one or two days after you give birth.

If you're both well, you and your baby will normally be able to go home after 24 hours.

You should have a blood test to check for diabetes 6 to 13 weeks after giving birth. This is because a small number of women with gestational diabetes continue to have raised blood sugar after pregnancy.

If the result is normal, you'll usually be advised to have an annual test for diabetes. This is because you're at an increased risk of developing type 2 diabetes – a lifelong type of diabetes – if you've had gestational diabetes.

^^ Back to top

The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website nhs.uk
Last Updated: 10/11/2020 14:50:28