What is gestational diabetes?
Gestational diabetes mellitus (GDM) is a type of diabetes that arises during pregnancy (usually during the second or third trimester).
In some women, GDM occurs because the body cannot produce enough insulin to meet the extra needs of pregnancy. In other women, GDM may be found during the first trimester of pregnancy. In these women, the condition most likely existed before the pregnancy.
A test called an Oral Glucose Tolerance Test (OGTT) is used to diagnose GDM. An OGTT involves a blood test before breakfast, then again two hours after a glucose drink.
How will I know if I have it?
At the booking appointment you will be assessed for risk factors that can make you more likely to have gestational diabetes. These include:
- a family history of Type 2 diabetes (parent, brother or sister)
- an unexplained stillbirth or neonatal death in a previous pregnancy, and/or
- a very large infant in a previous pregnancy (4.5kg or over)
- you have had gestational diabetes before
- your family origin is South Asian, Black Caribbean or Middle Eastern.
If you have any of these characteristics you should be offered a test for gestational diabetes.
How will it affect my baby?
In most cases, Gestational diabetes comes to light during the second trimester of pregnancy. Since the baby’s major organs are fairly well developed at this stage, the risk to the baby is lower than for women with Type 1 or Type 2 diabetes.
However, babies of women who had blood glucose problems that were undiagnosed before pregnancy, have a higher risk of malformations. The degree of risk depends on how long blood glucose levels have been high and on how high the levels have been.
What is the treatment?
Often, blood glucose levels can be controlled by diet. You will be referred to a dietitian who will advise you about healthy eating. If your blood glucose cannot be controlled by diet, you may need tablets or insulin to treat your diabetes (this applies to about 10 - 20 per cent).
Blood glucose target levels are the same as for women with Type 1 or Type 2 diabetes and you will receive the same specialised care as they do.
Will it go away after my baby is born?
Usually it does. Before you are discharged to the care of your GP, your blood will be tested to make sure the glucose levels have returned to normal. You should have a fasting blood test six weeks after your baby is born and then every year. If you took medication (tablets or insulin) during your pregnancy, you will be able to stop them after your baby is born.
Women with GDM have a 30 per cent risk of developing Type 2 diabetes during their lifetime (compared to a ten per cent risk in the general population).
About five to ten per cent of women with GDM develop Type 1 diabetes sometime in their life. These women have a slowly developing form of Type 1 that is ‘unmasked’ during pregnancy.
Will I get gestational diabetes with other pregnancies?
You are more likely to develop GDM again if you have had it in previous pregnancies; but, if you are overweight and lose weight, you may cut your risk of having GDM again. If you plan another pregnancy you should be offered the opportunity to self-monitor your glucose levels, with an OGTT at 16-18 weeks which will be repeated at 28 weeks if normal.