What is gestational diabetes?

Gestational diabetes mellitus (GDM) is diagnosed when higher than normal blood glucose levels first appear during pregnancy. Between 3 and 8% of pregnant women will develop gestational diabetes around the 24th to 28th week of pregnancy, however, some may be earlier.

Pregnant women need two or three times more insulin than normal. If the body is unable to produce this much insulin, gestational diabetes develops.

If gestational diabetes is not well looked after it may result in problems such as a large baby, miscarriage and stillbirth.

Women who have had gestational diabetes are at an increased risk of developing type 2 diabetes. 

The official definition of gestational diabetes is diabetes which is first diagnosed during the current pregnancy. The diagnostic guidelines are currently under review and expected for official release in the very near future.
At present gestational diabetes (or GDM) is diagnosed with either a 1 hour, 50g glucose challenge test (GCT) or a 2 hour, 75g glucose tolerance test (OGTT); usually at around 28 weeks gestation if no or limited risk factors are identified, but can be diagnosed earlier in the pregnancy for those who have multiple risk factors.
Risk factors include: maternal age, family history of diabetes, ethnic background, maternal obesity, previously large for gestational age infant, poor obstetric history and/or polycystic ovarian syndrome (PCOS).
GDM is diagnosed if the 50g GCT result  is greater than 11.1 mmol/L or the OGTT is abnormal. A 1 hour GCT of 7.8-11.1 is inconclusive and results in this range usually result in an OGTT being arranged shortly afterwards. During the OGTT 3 blood samples are taken; fasting, one hour after the drink and 2 hours after the drink. The fasting level should be <5.5, the one hour result <10.0 and the 2 hour result <8.0 mmol/L. (As mentioned before these guidelines are under review and are expected to be adjusted shortly, based on results from 2 very large multinational studies).

Insulin requirements increase during the pregnancy and are highest in the third trimester, hence most women are diagnosed during this last trimester. Women diagnosed in the very early stages of pregnancy (first trimester) could in some cases have undiagnosed pre-existing diabetes. In most cases the treatment is the same: women are asked to follow a diet of lower carbohydrate meals which are spread across the day, to do regular physical activity and if blood glucose levels are not controlled to take insulin via subcutaneous injections.

If you like more information about gestational diabetes (or other forms of diabetes) feel free to contact me directly.

Gestational diabetes occurs during pregnancy. When gestational diabetes is well controlled, the risks to the baby and mother are greatly reduced. Women are at greater risk of developing type 2 diabetes after experiencing gestational diabetes. Gestational diabetes is diagnosed using an oral glucose tolerance test (OGTT). After the baby is born, the mother’s blood glucose levels usually return to normal.

Diabetes is a common condition in which there is too much glucose in the blood. The pancreas either cannot make insulin or the insulin it does make cannot work properly to control the level of glucose in the blood. Insulin is a hormone that is needed to transport glucose from the blood stream into cells where it is needed for energy. Between three and eight per cent of pregnant women will develop gestational diabetes. It is usually detected around weeks 24 to 28 of pregnancy, though it can develop earlier. Being diagnosed with gestational diabetes can be both unexpected and upsetting.

It can raise questions such as:
Will my baby be affected?
Will I have diabetes for the rest of my life?
What do I need to do to manage this condition?
Various health professionals will be involved in helping you manage gestational diabetes. You will be given information about how to test and monitor blood glucose levels, as well as dietary advice with a dietitian. Working closely with your doctor and healthcare team can help you to lower your blood glucose levels and keep them within the normal range.

Certain women are at increased risk of developing gestational diabetes. High risk groups include:
Women over 30 years of age
Women with a family history of type 2 diabetes
Women who are overweight or obese
Aboriginal and Torres Strait Islander peoples
Women of particular cultural groups, such as Indian, Chinese, Vietnamese, Middle Eastern, Polynesian and Melanesian women
Women who had gestational diabetes in a previous pregnancy.

The placenta produces hormones that help the baby to grow and develop, but these hormones can also interfere with the action of the mother’s insulin. This is called insulin resistance. As the pregnancy progresses, the mother’s energy needs increase and her insulin needs are also higher than normal. Some women are unable to produce extra insulin and blood glucose levels rise.

When the baby is born, the mother’s need for insulin returns to normal and diabetes usually disappears.

When the mother has gestational diabetes glucose crosses the placenta from mother to baby to meet the energy needs of the developing baby. If the mother’s blood glucose levels are raised, a greater amount of glucose crosses the placenta to the baby. To manage this extra amount of glucose, the baby produces more insulin. This can cause excessive growth and fat in the baby. If the mother’s blood glucose levels remain raised, the baby may be larger than normal.

Following delivery, the baby may experience low blood glucose levels, particularly if the mother’s blood glucose levels were raised before the birth.

Gestational diabetes can be monitored and treated and if well controlled, these risks are greatly reduced. The baby will not be born with diabetes.
Symptoms of gestational diabetes

Gestational diabetes usually has no obvious symptoms. If symptoms do occur, they can include:
Unusual thirst
Excessive urination
Tiredness
Thrush infections.
Diagnosis of gestational diabetes

Most women are diagnosed using a special test, which requires a blood sample to be taken after a glucose drink. These tests are usually performed between 24 and 28 weeks into the pregnancy, or earlier if the woman is at high risk.

There are two types of tests:
Glucose challenge test (GCT) – blood is taken and the glucose level is measured one hour after the drink. If this is above normal, an oral glucose tolerance test is required.
Oral glucose tolerance test (OGTT) – involves taking a blood sample after the woman has fasted overnight, A second blood sample is taken two hours after the woman has had a drink containing 75 grams of glucose. A diagnosis is based on the results of the OGTT.
Diagnosis of gestational diabetes is made if the fasting blood glucose is raised or the two-hour blood glucose is raised.