Gestational diabetes (diabetes in pregnancy)

Produced by Louise Abbott, Bupa Health Information Team, December 2011.

This factsheet is for women who have gestational diabetes (diabetes that develops in pregnancy), or for anyone who would like information about it. It doesn't provide information for women who already have diabetes and are pregnant or who would like to become pregnant.

Gestational diabetes is high blood sugar (glucose) that develops in some women when they are pregnant. It can lead to problems for mothers and their babies if the diabetes is left uncontrolled.

About gestational diabetes

Gestational diabetes means you have a high blood sugar level, but only during pregnancy. When you aren’t pregnant you don’t have diabetes. Around three to four in every 100 pregnant women will get gestational diabetes during their pregnancy.

Normally, your body releases a hormone (a chemical messenger carried in your blood) called insulin to make sure that sugar in your blood is taken up by your cells to turn into energy. Any excess sugar that isn’t needed is stored in your cells as fat. Usually during pregnancy your hormones, such as oestrogen and progesterone, cause an increase in insulin resistance. This means that your body needs to produce more insulin to have the same effect on blood sugar as it would have when you aren’t pregnant. This happens so that more sugar remains in your blood to be made available for your baby to use for energy and growth.

During pregnancy, your body naturally releases more insulin to overcome the effects of your pregnancy hormones. This ensures that any blood sugar not used by you, or taken up by your growing baby, is still stored. If you develop diabetes in pregnancy, it means that either your body isn’t releasing enough insulin, or your cells aren’t responding to it. The result is that your blood sugar level remains high. This can have a number of effects on you and your growing baby.

Gestational diabetes usually begins between weeks 13 to 28 of pregnancy and will go away after your baby is born. If you still have diabetes after the birth of your baby, it’s likely that you already had underlying diabetes, but it was only picked up because you were pregnant. In this situation you will need to have treatment.

Symptoms of gestational diabetes

Often you won’t have any symptoms of gestational diabetes. However, sometimes you might notice symptoms of having a high blood sugar level, which can include: 

• feeling thirsty more often than usual
• needing to urinate more often and passing larger amounts of urine than usual
• feeling tired

These symptoms are often associated with being pregnant.

These symptoms aren’t always caused by gestational diabetes, but if you have them, see your GP or obstetrician (a doctor who specialises in pregnancy and childbirth).

Complications of gestational diabetes

Gestational diabetes can lead to a number of complications if it isn’t controlled. You may be able to reduce your risk of many of these happening to you or your baby by carefully controlling your blood sugar level. 

Complications affecting you

Complications that can happen to you include:

• pre-eclampsia – high blood pressure during pregnancy that can lead to you having fits
• too much amniotic fluid (the fluid around your baby in your womb)
• premature labour – giving birth before 37 weeks of pregnancy
• problems during the birth that could lead to you needing a caesarean

You're also more likely to develop gestational diabetes in future pregnancies and are at a higher risk of developing type 2 diabetes later in life. You will need to be checked for type 2 diabetes regularly so that treatment can be started if needed.

Complications affecting your baby

Having a high blood sugar level during pregnancy can lead to your baby growing larger than would be expected. This is because he or she doesn’t use the excess sugar so it’s stored as fat in his or her body. This could make labour and birth more difficult. A particular concern is the increased risk of shoulder dystocia. This means that your baby’s head can be born, but his or her shoulders become stuck behind your pelvic bone. This can lead to a number of problems including injury to your baby’s shoulders or arms, damage to the nerves in his or her neck or, very rarely, brain injury as a result of a lack of oxygen. The staff at the hospital will advise you on the best way for your baby to be born safely.

Your baby may have low blood sugar (hypoglycaemia) for a few days after birth. This will be monitored and only needs treating if the sugar in your baby’s blood drops below a certain level.

There is a slightly higher risk of your baby having jaundice, which is fairly common in all newborns. Jaundice is caused by the build-up of bilirubin in the blood. Bilirubin is a yellow substance produced when red blood cells are broken down. The yellow tinge to his or her skin and eyes will fade over a couple of weeks and doesn’t usually require treatment. If treatment is required, your baby will be placed under ultraviolet lights to break down the bilirubin in his or her skin.

If your baby is born prematurely, there is a higher chance of him or her having a condition called respiratory distress syndrome. This is because his or her lungs are more immature as a result of the high sugar levels during pregnancy. This condition can lead to further complications for your baby, such as high blood pressure and infections. Your baby can be treated for these problems.

If you have gestational diabetes, there is a higher chance of your son or daughter being obese in later life. Your child will also be more at risk of developing diabetes when he or she is older.

Causes of gestational diabetes

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

• are overweight or obese
• have previously given birth to a large baby weighing 4.5kg or more
• had gestational diabetes in a previous pregnancy
• have a family history of diabetes (parent, brother or sister who has the condition)
• have polycystic ovary syndrome

Your family origins may also increase your risk of getting diabetes. The condition particularly affects people whose family backgrounds are South Asian (specifically women whose families come from India, Pakistan or Bangladesh), black Caribbean or Middle Eastern.

Diagnosis of gestational diabetes

Doctors differ in their opinions about when and how to test pregnant women for gestational diabetes so the timing of tests you have may differ from what is described here.

At your first antenatal appointment your GP will ask about your medical history and examine you. He or she will check for any risk factors you may have and, based on this, you may be offered tests to find out if you already have diabetes, or are at risk of developing the condition during your pregnancy. The tests involve taking a blood sample and for some of these you may need to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand.

If you don’t have any of the risk factors, you’re likely to be tested for gestational diabetes at an antenatal appointment when you’re between 24 and 28 weeks pregnant. This is because even without any risk factors, being pregnant can increase the likelihood of diabetes developing. You will be asked to drink a sugary drink and then have blood samples taken to see how well your body processes the sugar.

Treatment of gestational diabetes

Your GP will refer you to a clinic where the doctors and nurses are experienced in looking after pregnant women with diabetes. You will have more frequent antenatal appointments than women who don't have gestational diabetes.

The treatment for gestational diabetes aims to maintain your blood sugar level within the normal range for someone who doesn’t have diabetes. The blood sugar ranges for people without diabetes are shown below. The units are millimoles per litre (mmol/l), which is a measurement of the concentration of sugar in your blood.

• Before meals: 3.5 to 5.5mmol/l.
• Two hours after meals: less than 8mmol/l.

There are many different opinions about the ideal range to aim for when you have gestational diabetes. This is individual to you, so the target levels will be agreed between you and the doctors and nurses who are caring for you.

As a guide, the target levels that you may be expected to aim for are shown below.

• Before meals: 4 to 7mmol/l.
• Two hours after meals: less than 8.5mmol/l.

Self-help

Initially, your doctor or dietitian will advise you on ways to manage your gestational diabetes with diet and exercise changes. This may be all you need to do to keep your blood sugar level within the correct range and help to prevent complications of gestational diabetes. Eating a healthy, balanced diet and doing regular exercise may also help to prevent you getting type 2 diabetes in later life.

Studies have shown that eight in 10 women who have gestational diabetes are able to manage their blood sugar level through exercise and dietary changes alone.

The following healthy eating ideas can help to keep your blood sugar level stable and within the expected range.

• Include enough carbohydrates that release their energy slowly, such as wholemeal bread and pasta, oats, brown rice, potatoes, lentils and beans in your meals. These maintain your energy levels without increasing your blood sugar level too much.
• Eat a variety of lean protein, such as chicken, turkey and tuna (in water).
• Aim to eat up to two portions of oily fish each week, such as mackerel, sardines, salmon, trout and herring.
• Try to eat at least five portions of fruit and vegetables every day.
• Limit the amount of high sugar, salt and fatty food that you eat. These include cakes, biscuits, crisps and fried foods.

Regular moderate-intensity exercise, such as walking, helps to reduce your blood sugar level and promotes a sense of wellbeing. The National Institute for Health and Clinical Excellence (NICE) recommends that you do at least 30 minutes of activity that gets you slightly breathless each day.

You will need to regularly test your blood sugar level. You will be given advice on how to test it, how often and the level that you're aiming for. You will probably need to do a test every day.

Medicines

Around one to two women in 10 won't be able to control their gestational diabetes with diet and exercise and will need tablets or insulin injections.

If, after two weeks of making diet and exercise changes, you’re still having trouble controlling your blood sugar level, you will be offered different options for medicines that can reduce your blood sugar level.

You may be given tablets such as metformin, which is a medicine that will reduce the level of sugar in your blood.

If these sugar-reducing medicines aren’t enough to control your blood sugar level, you will be prescribed insulin to help you manage your gestational diabetes. You will need to take the insulin as an injection. You will be shown how to inject yourself and get advice on when to do this.

Side-effects

It's possible for you to develop hypoglycaemia (sometimes called a 'hypo'). This is when your blood sugar level becomes so low that you may pass out. This can happen if you take too much of your medicines or miss a meal. You may have symptoms of being pale, shaking, feeling hungry and sweating. Your doctor or specialist nurse will explain how to recognise the symptoms of hypoglycaemia, and what to do if it happens. For example, keeping a sugary, soft drink with you is a good idea so that you can drink this if you start noticing signs of hypoglycaemia.

If hypoglycaemia causes you to lose consciousness, you will need an injection of glucose in hospital. It's important that your family and friends know what to do if your blood sugar gets very low and you pass out. If you find it difficult to control your diabetes, you may be given an emergency injection – called glucagon – to keep at home for your family to use if you pass out.

After your baby is born

You and your baby will have your blood sugar levels monitored after he or she has been born to make sure these are back to normal.

Doctors recommend that it's best to breastfeed your baby within 30 minutes of birth to keep your baby's blood sugar at a safe level and then breastfeed every two to three hours thereafter.

If you were taking any medication for diabetes, you can stop these after your baby is born. You will need to have a blood sugar test at your six-week check-up to ensure that your blood sugar has returned to the expected level. If it hasn’t, you may be at risk of developing diabetes even though you’re no longer pregnant. You will be given further advice and possibly some medicines to manage this condition.

Prevention of type 2 diabetes

If you developed gestational diabetes when you were pregnant, you’re more at risk of getting type 2 diabetes later in life. You can help to prevent this happening by eating a healthy, balanced diet and maintaining a healthy weight. Doing regular exercise is also important – 30 minutes of moderate-intensity physical activity every day is recommended for adults.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.