What is gestational diabetes?

Gestational diabetes is when pregnant women, who were not known to have diabetes before pregnancy, have high blood sugar levels during pregnancy. Gestational diabetes affects about 4% to 8% of all pregnant women. Treatment includes correct diet and exercise, and possibly use of insulin. Untreated, it can lead to problems for both mother and baby. Gestational diabetes usually goes away after the birth, but the woman is at increased risk of it occurring in future pregnancies and of developing diabetes in later years.

Who is likely to develop gestational diabetes?

It is recommended that all pregnant women who:

• are 25 years or older
• were overweight before they became pregnant
• have a family history of diabetes
• are of non-European descent
• have previously had a large baby or abnormal pregnancy

...should be tested for gestational diabetes between the 24th and 28th weeks - around the sixth month of pregnancy. Women with gestational diabetes in an earlier pregnancy should be tested as soon as a new pregnancy occurs.

However, even women without these characteristics may still develop gestational diabetes and should consider being tested.

How is it detected?

The screening test measures your blood sugar response to glucose consumed in a drink. If this initial test is high, a fasting test over two hours is then carried out as well.

How can gestational diabetes affect you and your baby?

Untreated, the high sugar (and fat) in the blood of a woman with gestational diabetes can overfeed the baby while it is in the womb, leading to "macrosomia" or a "fat baby".  This can lead to a difficult birth with damage to the baby (such as damage to the shoulders), pain and damage to the mother and a greater chance of needing a caesarean section. Babies can also suffer from a very low blood sugar and breathing problems.

Because gestational diabetes affects the mother in pregnancy after the baby's body has been formed but while the baby is still busy growing it does not cause the kinds of birth defects sometimes seen in babies whose mothers had diabetes before pregnancy.

Furthermore, we now know that treatment can reduce the chance of bigger babies and of the baby having a low blood sugar at birth.

Treating gestational diabetes

Treatment is started as soon as possible and is geared towards keeping blood sugar levels equal to those of pregnant women who do not have gestational diabetes. Treatment includes eating a healthy diet and taking physical activity if possible. It may also include daily blood sugar testing and insulin injections. Help is provided by the local diabetes in pregnancy team.

Treating gestational diabetes helps lower the chances of having a bigger baby, a baby with low blood sugar at birth and the need for caesarean section. Staying with the treatment increases the chances of a healthy pregnancy and birth, and helps your baby avoid future health problems.

Looking ahead

Gestational diabetes usually goes away after pregnancy. But once you've had gestational diabetes, your chances are two out of three that it will return in future pregnancies. In a few women, however, pregnancy uncovers type 1 diabetes or type 2 diabetes. These women will need to continue diabetes treatment after pregnancy.

Half to two-thirds of women who have had gestational diabetes develop type 2 diabetes up to 25 years later and are tested for new diabetes every one to two years. Controlling bodyweight, making healthy food choices and taking regular exercise may help prevent diabetes after gestational diabetes.

Keeping concern in perspective

While gestational diabetes is a cause for concern, identifying gestational diabetes means that the right care can be put into place, at the right time, to help you and your baby have the best possible outcome. Knowing you have had gestational diabetes also lets you know of your future chance of permanent diabetes before it happens, giving you a chance to act early.

Original material provided by Professor David Simmons, Waikato Clinical School, University of Auckland, February 2005. Reviewed by everybody, September 2011.