What happens following an OGTT?

If you have had an oral glucose tolerance test (OGTT) and it is positive, this means you have gestational diabetes mellitus (GDM). Your doctor or midwife will let you know the result, and a clinic appointment will be made so that your on-going care can be planned with you. You may be asked to attend a special clinic for women with diabetes in pregnancy; specialists in the care of women with diabetes will see you at this clinic. These specialists will include an obstetrician and midwife (who may be different from the doctor and midwife you have seen before), a doctor who looks after people with diabetes (called a diabetologist), a dietician and a diabetic nurse specialist.

At your clinic visit, you will be asked about your usual diet: the foods you eat, the amount of food and the times you eat, and you will also be asked about the amount of physical activity you do in a usual day. The specialist team will advise you about how much food to eat now you have GDM, which foods to eat, which foods to avoid and what a good level of physical activity is. The team will also explain if you need any medications and how to monitor your blood glucose. You need to monitor your blood glucose because every person responds differently to treatment, and therefore treatment often needs to be adjusted to control your blood glucose properly.

Treatment aims to reduce blood glucose levels. For most women, treatment will start with adjustment of diet and physical activity. If blood glucose is not reduced enough, then tablets to improve insulin sensitivity or insulin will be offered.

Diet to reduce glucose levels

A healthy balanced diet is advisable throughout life, during pregnancy and for women with GDM. For women with GDM, it is particularly important to understand what foods consist of in terms of ‘food groups’ – i.e., carbohydrates, protein and fats. A healthy diet is a balanced diet that includes a balance of food groups to ensure all the nutrients needed are obtained, including vitamins and minerals. Processed foods should be limited. In pregnancy, supplements including vitamin D, iron and folic acid are often recommended for all women.

Carbohydrates are a very important food group for women with GDM. Carbohydrates come from grains (e.g. bread and pasta), fruits (e.g. apples and bananas) and vegetables (e.g. potatoes, carrots and parsnips). During digestion, carbohydrates are easily broken down into simple sugars, like glucose, which is the body’s main source of energy. Therefore, eating carbohydrates will quickly affect blood glucose levels: eat a large amount and blood sugar goes up a large amount; eat a small amount and blood sugar goes up a small amount.

The hospital team will work with you to find the best amount of carbohydrate to keep your blood sugar levels as close to normal as possible and without too many large peaks and troughs; you will also be advised on the amount of the other food groups to eat too. You may be asked to monitor or ‘count’ the grams of carbohydrate you eat at each meal to help make sure you get the right amount and to keep a food diary to help understand your eating pattern. Your total carbohydrate allowance for one day should be spread pretty evenly across your meals, and you may need to include a snack, such as a piece of fruit or a couple of crackers, before you go to bed to make sure your blood glucose levels are adequate overnight. Not eating enough carbohydrate may cause problems such as low blood sugar, which can lead to low energy, nausea and hypoglycaemia (low blood glucose that leads to ‘fainting’).

You will probably be advised to limit the amount of sugary foods like cakes, pastries and sweets you eat.

Physical activity to improve insulin sensitivity

There is very limited quality research about the effects of exercising in pregnancy. The National Institute for Health and Care Excellence (NICE) recommends that all pregnant women should begin or maintain a regular exercise regimen in pregnancy. NICE suggests this should be 30 minutes per day of moderate intensity recreational exercise, such as swimming or brisk walking and strength conditioning exercises. If a woman has not exercised routinely, they should begin with no more than 15 minutes of continuous exercise, three times per week, increasing gradually to daily 30-minute sessions.

It is unclear what amount of physical activity helps control blood sugar for women with GDM. The specific amount depends on the physical activity level before pregnancy and whether or not there are any other health concerns. The team you see will be able to advise you about physical activity.

The effect of diet and physical activity adjustment will usually be monitored for 1-2 weeks to see if these changes control your blood glucose levels. If blood glucose remains high, you may need medications or insulin to help control your blood glucose. It is important to know, however, that the blood glucose of many women with GDM can be controlled with diet and physical activity only.

Metformin to improve insulin sensitivity

Metformin is a medication taken as a tablet; it has been used for many years outside of pregnancy to control blood glucose levels in people with type 2 diabetes. Research shows that metformin can be used safely in pregnancy, and NICE recommends its use to control blood glucose levels if diet and physical activity is ineffective. Metformin can cause side effects including digestive upset; if you experience side effects, you should tell your doctor. Metformin use can also lead to low blood glucose (hypoglycaemia), so if you experience feelings of faintness and nausea (signs of hypoglycaemia), you should take a glucose tablet or similar food to counteract the low glucose level. Your team will tell you what to do if you have symptoms of hypoglycaemia and advise you about foods to carry with you, ‘just in case’.

Insulin to help store glucose

Insulin is the hormone that ensures blood glucose is converted to glycogen and stored properly. Sometimes diet, physical activity and even metformin do not control blood glucose enough, and so your doctor may suggest insulin treatment if your blood sugar is particularly high. Insulin is given using a syringe with a very small needle, which allows insulin to be injected just under the skin. The team caring for you will teach you how to give yourself insulin if you need it and tell you when and how much insulin to give yourself. Insulin use can cause low blood glucose (hypoglycaemia), so it is important you understand what to do if this happens (see above under metformin).

Monitoring blood glucose levels

When you have GDM, knowing your glucose level is important so you can modify your diet and physical activity regimen; the aim is to try and keep glucose levels within the normal range and without too many large increases or decreases. This should get easier as you get to know how your body responds to the foods you eat and the physical activity you take. The only way to check your blood glucose levels is to test your blood. You can do this yourself at home with a simple small machine that you will be given by your team, who will show you how to monitor your blood glucose, so don’t worry, but here’s a summary of what you would need to do:

1. Wash your hands with warm water and soap.
2. Prick your finger with a small needle called a lancet. (Use each lancet only once and be careful when you throw away used lancets. You will be given a special box to dispose of the sharp items required to test your blood or give yourself insulin. This box will be disposed of by your team when it is full – just take it to them.) Squeeze out a drop of blood from the finger you pricked.
3. Place the drop of blood on the target spot of your glucose meter or onto the paper strip that fits into the meter.
4. Wait a few minutes (how long you need to wait depends on the machine). The meter will tell you your blood sugar level.

What extra tests and scans may you be offered?

Because higher than normal blood glucose can lead to increased growth of your baby, extra ultrasound scans may be arranged to monitor growth. How often these scans happen will depend on you, how well your blood glucose levels respond to treatment and how your baby is growing.

You may be advised that it would be best to deliver your baby by 40 weeks (your ‘due’ date) or sometimes sooner depending on how your baby has grown and how your health is. Induction of labour (starting labour artificially) may be advised because all babies get larger as pregnancy continues, so to prevent excessive growth, birth may be the only option.

What happens after birth if you are diagnosed with GDM?

After your baby is born, treatment of your GDM will be stopped, but your blood glucose levels will still be monitored. For most women, blood glucose levels return to normal immediately without any treatment. For a small proportion of women, however, glucose levels may rise without treatment; these women may require on-going treatment after their baby is born and may be diagnosed with type 2 diabetes. Even if glucose levels are normal immediately after birth (while you are still in hospital), an OGTT will be offered at six weeks following your baby’s birth and then yearly after that. These OGTTs are offered because women that have had GDM are more likely to develop type 2 diabetes. GDM does not cause type 2 diabetes, but it is a risk characteristic, which means women with this characteristic are more likely to develop type 2 diabetes.

Does having GDM affect future pregnancies?

Having GDM in one pregnancy does make it more likely in the next, so if you have had GDM and become pregnant again, you will probably be offered an OGTT in early pregnancy. You can reduce your risk of GDM in a future pregnancy if you make changes to the modifiable risk characteristics that make GDM more likely (see below).

Can anything be done to reduce the risk of GDM in a future pregnancy?

Risk characteristics can be divided into non-modifiable and modifiable. Non-modifiable risk characteristics cannot be changed; they include ethnicity and family history of diabetes. Modifiable risk characteristics, however, are characteristics such as weight, diet and physical activity; they are characteristics that can be changed or ‘modified’ to reduce risk. The simplest, but potentially most challenging, modification is to reduce weight to within normal limits and to increase physical activity. Achieving a healthy weight can greatly reduce the risk of GDM and type 2 diabetes and many other health conditions. Your GP or midwife will be able to tell you what weight loss help is available in your area.

Main Points

• A positive result on an oral glucose tolerance test means you have gestational diabetes.
• If you have been diagnosed, you may be asked to attend a special clinic for women with diabetes in pregnancy, where you will be seen by several specialists.
• Treatment for gestational diabetes aims to reduce blood glucose levels.
• The staff at the clinic will advise you of the recommended amount of physical activity and which diet to adopt to help you manage your diabetes. For many women, this alone helps them to manage the condition.
• Because every woman will respond to treatment differently, it’s important to monitor blood glucose levels so that treatment can be adjusted if need be.
• A healthy balanced diet is advised for women with gestational diabetes.
• Carbohydrates are an important food group, as they quickly affect blood glucose levels. Your medical team will help you find the best amount of carbohydrate to keep your blood sugar at a normal level. You might be asked to keep a food diary so you’re able to keep track of the amount of carbohydrate you’re eating.
• You should limit sugary foods as much as you can.
• If you have gestational diabetes, the specific amount of physical activity depends on your activity level before pregnancy and whether or not there are any other health concerns. Your health team will advise you on this.
• If your blood glucose remains high after these lifestyle changes, you may be offered medication or insulin.
• Metformin is taken as a tablet and can lower blood sugar.
• Insulin is given using a syringe with a small needle. The team caring for you will show you how to give yourself insulin.
• To monitor your blood sugar levels throughout pregnancy, you will need to take a blood sample using a device, which your team will show you how to use.
• You may be offered additional ultrasound scans so the growth of your baby can be monitored.
• Depending on how your baby has grown, it may be recommended for your labour to be induced before 40 weeks to prevent excessive growth.
• Having GDM in one pregnancy makes it more likely that you’ll develop it in your next pregnancy, but making changes to modifiable risk characteristics will reduce the likelihood of this happening.

Further information

Brown J, Alwan N A, West J, Brown S D, Mckinlay C J D, Farrar D, Crowther C A (2017). Lifestyle interventions for the treatment of women with gestational diabetes. Cochrane Database of Systematic Reviews(5): CD011970.

Farrar D (2016). Hyperglycemia in pregnancy: prevalence, impact, and management challenges. Int J Women’s Health 8: 519-527

Farrar D, Simmonds M, Bryant M, Sheldon T A, Tuffnell D, Golder S, Lawlor D A (2017). Treatments for gestational diabetes: a systematic review and meta-analysis. BMJ Open 7(6).

Farrar D, Simmonds M, Griffin S, Duarte A, Lawlor D A, Sculpher M, Fairley L, Golder S, Tuffnell D, Bland M, Dunne F, Whitelaw D, Wright J, Sheldon T A (2016). The identification and treatment of women with hyperglycaemia in pregnancy: an analysis of individual participant data, systematic reviews and an economic evaluation. HTA 20(86).