Fact sheet: Test for gestational diabetes

I am pregnant. Why are all pregnant women offered a test for gestational diabetes?

This fact sheet explains why in Germany all pregnant women are offered a test for gestational diabetes. You will be given information about how the test is done, what consequences gestational diabetes can have, and what treatment options are available.

The most important information:

• In gestational diabetes, blood sugar levels are high. This somewhat increases the risk of certain rare birth complications, yet this risk can usually be normalized by changing the diet.
• If gestational diabetes is diagnosed, it makes it possible to do something about it yourself.
• The vast majority of women who develop gestational diabetes experience an otherwise normal pregnancy and go on to give birth to a healthy baby.
• Having gestational diabetes does not mean that you have permanent diabetes (type 1 or type 2 diabetes).

You have a right to be tested for gestational diabetes.
Of course, you also have the right to decide not to have the test.

What is gestational diabetes?

For most women, blood sugar levels remain normal during pregnancy. But if blood sugar levels do exceed a certain value, experts call this gestational diabetes. Very high blood sugar levels may be a sign that a woman had developed diabetes before pregnancy without knowing it. These women are provided with special care that their doctors will describe to them.

Elevated blood sugar levels are more common in women who are severely overweight, who have relatives with diabetes, or who have previously had gestational diabetes. Your doctor might already ask you about these factors early in your pregnancy and then advise you to take a test.

What consequences can gestational diabetes have and how does treatment affect this?

Every pregnant woman certainly hopes for normal and healthy pregnancy and birth. So it is important to know that most pregnant women who have gestational diabetes also have a baby that develops in a perfectly normal way. There are women, however, who benefit from treatment.

Babies born to women who have gestational diabetes have a somewhat heavier birth weight on average. This is not a reason for concern in and of itself. Yet if the baby is larger, there is often a delay in the birthing process after the head appears. In such a case of what is called “shoulder dystocia” midwives and doctors need to react quickly, and injury to either mother or child can sometimes occur. Even though these injuries seldom have lasting consequences, shoulder dystocia is less common if gestational diabetes is treated. Trials showed that while without treatment in 3 to 4 out of 100 women with gestational diabetes shoulder dystocia occurred, with treatment this was only the case in 1 to 2 out of 100 births.

If blood sugar levels are elevated, the risk of what is called pre-eclampsia also rises. This pregnancy condition is also rare and is associated with excess protein in the urine. Blood pressure rises and fluids accumulate in the body. Left untreated, pre-eclampsia can harm both mother and child. From what we know today, this can be prevented by treating gestational diabetes.

How is gestational diabetes diagnosed?

The best method for diagnosing gestational diabetes is taking a glucose test (glucose tolerance test). The test measures how the body reacts to a large amount of glucose (sugar). It carries no risk to the mother or baby, but some women find drinking the sweet liquid unpleasant.

The glucose test is offered in the sixth or seventh month of pregnancy. If you agree to have it, you will first take a glucose challenge test. For this test you will drink a glass of water that contains 50 grams of dissolved sugar. You do not need to fast beforehand. One hour later, blood will be taken from a vein in your arm to determine the blood sugar level. If the value is below 7.5 millimoles per liter (mmol/L, about 135 mg/dL), the results are considered normal and no more testing is done.

If an elevated level is found in the glucose challenge test, it is still not considered a final diagnosis. It only serves to determine which women will be offered a second and final test. This second test, called the oral glucose tolerance test, is more involved. For the test, the pregnant woman must fast beforehand, which means not eating or drinking anything but water for at least eight hours. The first step in this test is taking blood. After this the woman drinks a sugar solution containing 75 grams of glucose. Blood is taken from an arm vein again after one hour and after two hours. If any of the following three blood sugar values is exceeded, gestational diabetes will be diagnosed:

• After fasting: 5.1 mmol/L (92 mg/dL)
• After one hour: 10.0 mmol/L (180 mg/dL)
• After two hours: 8.5 mmol/L (153 mg/dL)

The results are documented in the maternity records. In Germany, the costs of both of these tests will be covered by statutory health insurance funds.

How can gestational diabetes be treated?

High blood sugar levels can usually be lowered enough solely by making changes in diet and getting more exercise. Women who are affected can have a special consultation about this. Only few women with gestational diabetes have such consistently high blood sugar levels that they should inject insulin. Other types of diabetes medications are not approved for use during pregnancy.

After giving birth, women who have had gestational diabetes are offered another glucose test to be sure that their blood sugar levels have returned to normal. If that is the case, no further treatment is needed. It is true, however, that women who have had gestational diabetes are more likely to develop type 2 diabetes later in life.

Dealing with a diagnosis of gestational diabetes

A diagnosis of gestational diabetes often comes out of the blue. There are no noticeable symptoms. Concern about the child’s wellbeing and the woman’s own state of health can be a burden during the pregnancy. And the changes that are part of treatment may also take some getting used to. But they can quickly become a usual part of your routine. And it is important not to lose sight of one thing: the vast majority of children will be born healthy even if their mother has gestational diabetes.

You can find comprehensive information on this topic in our feature “Gestational diabetes”.

Author: Institute for Quality and Efficiency in Health Care (IQWiG)

© IQWiG (Institute for Quality and Efficiency in Health Care)