What is gestational diabetes?
Diabetes that develops during the second and third trimester of pregnancy is known as gestational diabetes mellitus (GDM). It occurs because your body cannot produce enough insulin (a hormone important in controlling blood glucose) to meet its extra needs in pregnancy, and subsequently results in high blood glucose levels.
How common is gestational diabetes?
GDM is very common, as it may affect up to 18 in 100 women during pregnancy. You are more likely to develop GDM if you have any of the following risk factors:
- Your body mass index (BMI) is 30 or higher
- You have previously given birth to a large baby, weighing 4.5 kg or more
- Previous GDM
- Family history of diabetes ( parent, brother or sister with diabetes)
- Your family origin is South Asian, Chinese, African-Caribbean or Middle Eastern.
How will you be checked for gestational diabetes?
If you have any of the above risk factors, you should be offered a glucose test during your pregnancy. This may be a simple blood test in early pregnancy and/or a glucose tolerance test (GTT) when you are between 24 and 28 weeks pregnant. If you have had GDM in a previous pregnancy, you may be offered GTT, or a kit to check your own blood glucose levels, early in pregnancy (around 16 weeks), as well as a GTT at 24–28 weeks.
A GTT involves fasting overnight (not eating or drinking anything apart from water):
- In the morning, before breakfast, you will have a blood test. You are then given a glucose drink.
- The blood test is repeated 1–2 hours later to see how your body reacts to the glucose drink.
What does gestational diabetes mean for you and your baby?
Most women who develop diabetes in pregnancy have healthy pregnancies and healthy babies. Occasionally GDM can cause serious problems, especially if it goes unrecognised. The early diagnosis and treatment of GDM reduces these risks, that’s why it is important to control the level of blood glucose during pregnancy.
If your blood glucose is too high, your baby will produce more insulin, which can make your baby grow bigger and increases the likelihood of having your labour induced, caesarean section, serious birth problems and stillbirth. These risks are higher if GDM is not detected and controlled. A baby that is making extra insulin may have low blood glucose levels after birth and is more likely to need additional care in a neonatal unit. Your baby may also be at greater risk of developing obesity and/or diabetes in later life.
Will you need extra care during pregnancy?
If you are diagnosed with GDM, you will be under the care of a specialist multidisciplinary team, which will usually include a doctor specialising in diabetes (endocrinologist), an obstetrician and dietician with special interest in Diabetes.
- Healthy eating and exercise
The most important treatment for GDM is a healthy diet and exercise, as GDM usually improves with these changes although some women, despite their best efforts, need to take tablets and/or give themselves insulin injections. You should have an opportunity to talk to a dietician about choosing foods that will help to keep your blood glucose at a healthy level.
- Monitoring your blood glucose
Following the diagnosis of GDM, you will be shown how to check your blood glucose levels and told what your ideal level should be. In case it does not reach a satisfactory level after 1–2 weeks, or if an ultrasound scan shows that your baby is larger than expected, you may need to take tablets or give yourself insulin injections.
- Monitoring your baby
You should be offered extra ultrasound growth scans to monitor your baby’s growth more closely.
Advice and information
During your pregnancy, your obstetrician and midwife will give you information and advice about:
- Planning the birth, including timing and types of birth, pain relief and changes to your medications during labour and after your baby is born
- Looking after your baby following birth
- Care for you after your baby is born including contraception.
Will you need treatment?
Up to one in five women with GDM will need to take tablets and/or have insulin injections to control their blood glucose during pregnancy. The treatment should be personalised for each pregnant woman and this will be advised by your healthcare team. If you do need insulin, your endocrinologist will explain exactly what you need to do, in terms of how to inject yourself with insulin, how often to do it and when you should check your blood glucose levels.
When is the best time and mode of delivery for your baby to be born?
Ideally you should have your baby between at 38 and 40 weeks of pregnancy, depending on your individual circumstances. If your ultrasound scans have shown that your baby is large, your obstetrician will discuss the risks and benefits of vaginal birth, induced labour and caesarean section with you.
What happens in labour?
It is important that your blood glucose level is controlled during labour and birth and it should be monitored every hour during labour to ensure it stays at a satisfactory level. If your blood sugars are increased in labour, you may be advised to have an insulin drip to help control your blood glucose level. During labour, your baby’s heart rate should be continuously monitored.
What happens after your baby is born?
- Breastfeeding is best for babies, and there’s no reason why you shouldn’t breastfeed your baby if you have GDM. Whichever way you choose to feed your baby, you should start feeding him or her as soon as possible after birth, and then every 2–3 hours to help your baby’s blood glucose stay at a safe level.
- Your baby should have his or her blood glucose level tested a few hours after birth to make sure that it is not too low. Your baby may need to be looked after in a neonatal unit if he or she is unwell, needs close monitoring or treatment, needs help with feeding or was born prematurely.
- GDM usually gets better after birth and therefore you are likely to be advised to stop taking all diabetes medications immediately after your baby is born. Before you go home, your blood glucose level will be tested to make sure that it has returned to normal.
- You should have a test to check your blood glucose level after an overnight fast or a GTT about 6–8 weeks after your baby is born. It is important that you attend, as a small number of women continue to have diabetes after pregnancy.
What follow-up should you have following childbirth and in future pregnancies?
You will be offered a postnatal appointment during which the result of your blood glucose test or GTT will be discussed with you. If your blood glucose levels are still high, you will be followed up by your endocrinologist.
Women who have had GDM have a one in three chance of developing type 2 diabetes within the following 5 years, therefore you will be advised to have a fasting blood glucose test once a year. Further advice and information will be provided about your lifestyle, including diet, regular physical exercise and weight control (having the right weight for your height), to reduce the risk of developing diabetes in the future. Finally, if you are planning to become pregnant, you should start taking a high dose (5mg) of folic acid daily before you stop contraception for at least three months.
Dr Efterpi Tingi
Consultant Obstetrician and Gynaecologist
