Gestational diabetes: Q and A
Q. What is gestational diabetes?
A. Gestational diabetes is a temporary form of diabetes that happens during pregnancy. It is different from having diabetes before pregnancy and then getting pregnant.
Gestational diabetes is usually diagnosed in the second and third trimesters of pregnancy. It typically starts in the 24th to 28th weeks and goes away after the baby is born.
Q. Am I at risk of gestational diabetes?
A. Gestational diabetes affects between 5 and 10 per cent of pregnancies in Australia. Women of certain ethnic backgrounds — Indian, Chinese, Vietnamese, Middle Eastern, Polynesian/Melanesian, and Australian Aboriginal or Torres Strait Islander — are more at risk of developing gestational diabetes than women of Anglo-Celtic backgrounds.
Other factors can also increase your risk. These include:
- being overweight;
- having a family history of type 2 diabetes;
- having had gestational diabetes in a previous pregnancy;
- having had difficulty carrying a pregnancy to term;
- being older than 30; and
- previously having a very large baby (more than 4.5 kg).
Q. How would I know if I had gestational diabetes?
A. Gestational diabetes does not usually give rise to symptoms. For this reason it is important to be tested during pregnancy, usually between 26 and 28 weeks.
The symptoms that may occur include excessive fatigue, being thirsty all the time and increased urination.
Q. What is the test for gestational diabetes?
A. The screening test is called a glucose challenge test. It involves you drinking either a 50 gram or 75 gram glucose solution and then a blood sample being taken an hour later. If the one-hour reading of your blood glucose is high, you may be asked to have another test known as a glucose tolerance test on another day to confirm the diagnosis of gestational diabetes.
The 75 gram glucose tolerance test is performed on women who have an abnormal glucose challenge test result, as well as any women at high risk of developing gestational diabetes, such as those with a history of the condition, or who are from a high-risk racial or ethnic group. This is usually done after you have followed a high carbohydrate diet for 3 days, under your doctor’s instruction.
Q. What does gestational diabetes mean for me?
A. If you have a high blood glucose reading on the glucose tolerance test it means that natural hormones secreted by your placenta during pregnancy have increased your body’s resistance to insulin; in other words, your body's cells are not responding normally to insulin. This means that your body needs much more insulin than usual to carry out insulin’s job of helping the body cells and muscles to take up glucose from the bloodstream after a meal. The result is that the glucose stays around in the bloodstream, hence the high glucose reading of your blood test.
Q. Does this mean that I will develop full-blown diabetes?
A. Having gestational diabetes does put you at risk of developing diabetes later on in life. This is why it is important to follow a healthy diet, maintain a healthy weight, and to exercise regularly, as these things can minimise your risk of developing diabetes.
Usually after the placenta is delivered, a woman’s blood glucose levels go back to normal. Women with gestational diabetes will usually have another glucose tolerance test 6 to 12 weeks after having the baby to make sure that their blood glucose has stayed at a normal level. For some women, though, their blood sugar levels will remain high after giving birth and these women may have to continue having treatment.
It is also advised that all women who have had gestational diabetes have a fasting or random blood glucose test every year, or a glucose tolerance test every 2 years. This is because having gestational diabetes increases a woman's risk of developing type 2 diabetes.
Q. Will my baby have a birth defect?
A. Gestational diabetes in a mother should not cause birth defects in her unborn child. Gestational diabetes usually develops in late pregnancy, in the second and third trimesters, when the child is already well-formed.
However, if gestational diabetes goes undiagnosed and is not treated, there is a higher risk of certain problems in the baby such as:
- high birth weight (sometimes this means the baby needs to be delivered early, but it may not be sufficiently well developed, which can lead to problems such as breathing difficulties or jaundice — also, a high birth weight can make vaginal delivery difficult or impossible, and the baby may be injured during birth); and
- low blood glucose levels (hypoglycaemia) after birth.
Q. What happens if gestational diabetes isn’t treated?
A. It is not good for your baby if extra glucose from your blood is crossing the placenta, and going into the baby’s bloodstream. The high blood glucose levels of the baby will make it produce extra insulin to try to get rid of the extra glucose. The extra glucose can also feed the baby up, which is why women with untreated gestational diabetes give birth to big babies.
If the baby has been pumping out extra insulin to deal with the excess glucose coming its way across the placenta from the mother, when the baby is born, it can suffer from low blood glucose. This happens because suddenly, the extra glucose the baby has been receiving has gone, but the baby’s pancreas is still secreting lots of insulin to take the glucose out of the bloodstream. Babies at risk usually have their blood glucose monitored after birth.
In addition, pregnant women with gestational diabetes have an increased risk of developing a pregnancy-related condition called pre-eclampsia, which is characterised by high blood pressure. This can be dangerous for both the mother and the unborn baby.
The good news is that if you can achieve good blood glucose control during pregnancy, a healthy baby and a safe delivery are likely.
Q. What is the treatment for gestational diabetes?
A. Treatment for gestational diabetes will focus on bringing your blood glucose levels within the normal range and keeping tight control of them. Most women can achieve good control with diet and exercise, but others may have to take insulin.
Your doctor will probably advise that you see a dietitian or a diabetes educator to help you with your diet. They will be able to advise you about low glycaemic index foods, and ensure that your dietary intake is rich in vitamins and nutrients for your growing baby. While it is important not to over-eat, it is also important not to under-eat, as this too can affect the baby's growth.
If diet and exercise measures don’t give you good control of your blood glucose, your doctor may advise that you start on insulin. At present, there is limited information on the safety in pregnancy of oral medications used to control blood glucose.
Q. Will I have to monitor my blood glucose levels?
A. Yes, it’s highly likely. Self-monitoring of your blood glucose levels (blood sugars) is the best way of knowing whether you have achieved good control of your blood glucose levels. Usually you will be advised to take at least one fasting measurement (before meals when you have an empty stomach) and another measurement one to 2 hours after you have eaten. You should record all your results in a home glucose diary.
Monitoring of your blood glucose is done by pricking your finger with a special device. There are several different types of these devices available and they aim to make it as easy and as painless as possible. A drop of blood is then placed on a special test strip. The strip will change colour according to the amount of glucose in your blood. You can match it to a colour chart printed on the container and read off your blood glucose level.
Another method of measuring your blood glucose level is with a blood glucose meter. You will still need to put a drop of blood onto a strip, but the strip is inserted into the meter for reading. Some other meters require you to put the strip into the meter before the blood is applied.
Q. What if I need insulin?
A. For some women, diet and exercise will not be enough to bring their blood glucose into the required range. If this is the case, you will probably need to have insulin injections.
Based on what times of day your blood glucose readings are high, members of your health team will advise you when you should inject insulin. If your glucose levels are staying high after a meal, you will probably be advised to inject short-acting insulin before meals.
Q. What are my chances of getting gestational diabetes again in a later pregnancy?
A. Once you’ve had gestational diabetes, the chance of you having it again in any future pregnancy is increased. Following a healthy diet and taking regular exercise will help to reduce your chance of this happening.
Q. What does having gestational diabetes mean for my future?
A. As mentioned, your chance of developing it again in further pregnancies is increased. Plus the chance of you developing type 2 diabetes is also increased. Following a healthy diet, keeping your weight at a safe level, and having regular physical activity will help to reduce your chances of these things happening. Your doctor will probably recommend that you also have your blood sugar level checked regularly.
Last Reviewed: 07 September 2009
- 1. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Diagnosis of gestational diabetes mellitus [2008, Jun; accessed 2009, Sep 18]. Available at: http://www.ranzcog.edu.au/publications/statements/C-obs7.pdf
2. Therapeutic Guidelines (eTG). Gestational diabetes. In: Endocrinology guidelines [updated 2009, Jun; accessed 2009, Sep 18]. Available from: http://www.tg.org.au/
3. MayoClinic.com. Gestational diabetes [updated 2009, Mar 28; accessed 2009, Sep 10]. Available at: http://www.mayoclinic.com/health/gestational-diabetes/DS00316
