Development of gestational diabetes
In pregnancy, the placenta produces hormones that help the baby grow and develop. These hormones also decrease the action of the mother’s insulin. This is called insulin resistance. Because of this insulin resistance, the need for insulin in pregnancy is two or three times higher than normal.
Consequently, during pregnancy, the mother’s body needs to produce higher amounts of insulin to keep her blood glucose levels within the normal range. If her body is unable to produce more insulin to meet her needs, gestational diabetes develops.
Women at risk of gestational diabetes
Between three and eight per cent of pregnant women develop gestational diabetes. It is usually detected around weeks 24 to 28 of pregnancy, although it can develop earlier. Being diagnosed with gestational diabetes can be both unexpected and upsetting.
Certain women are at increased risk of developing gestational diabetes. This includes women who:
are over 30 years of age
have a family history of type 2 diabetes
are overweight or obese
are of Aboriginal and Torres Strait Islander descent
are of particular cultural groups, such as Indian, Chinese, Vietnamese, Middle Eastern, Polynesian and Melanesian
have previously had gestational diabetes
take some antipsychotic or steroid medications
have previously had a baby whose birth weight was greater than 4,500 grams (4.5 kg)
have had a previous complicated pregnancy.
Some women with no risk factors also develop gestational 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 (yeast infections).
Diagnosis of gestational diabetes
Most women are diagnosed using a pathology test, which requires a blood sample to be taken before and 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.
With the new diagnostic guidelines, a pregnancy oral glucose tolerance test (POGTT) is recommended. This involves taking a blood sample after fasting overnight. Further blood samples are taken one and two hours after you have a drink containing 75 grams of glucose. A diagnosis is based on the results of the POGTT. Diagnosis of gestational diabetes is made if the fasting blood glucose is raised or the two-hour blood glucose is raised (or both).
Some centres may be still using the Glucose Challenge Test (GCT). A sweet glucose drink is given and the blood glucose measured one hour after the drink. If this is above normal, an oral glucose tolerance test is required. This test is no longer considered part of diagnostic testing as it is not specific or sensitive enough for diagnosing GDM.
Treatment for gestational diabetes
It is important to keep the mother’s blood glucose in the recommended range by having her doctor treat and monitor GDM. During pregnancy, glucose crosses the placenta from mother to baby to meet the energy needs of the growing baby. If the mother’s blood glucose levels are higher than normal, extra glucose will cross the placenta to the baby.
To deal with this extra glucose, the baby then makes more insulin. Insulin makes the baby grow larger more quickly. If the mother’s blood glucose levels remain high, the baby may become larger than normal. This can lead to problems during and after birth.
Keeping blood glucose in the recommended range also helps reduce the baby’s risk of being overweight in childhood and developing type 2 diabetes later in life.
Management of gestational diabetes
Health professionals (such as your doctor, dietitian, diabetes educator or diabetes specialist) can help you understand what you need to do and will support you in managing your gestational diabetes.
Some advice may include:
diet – eating a varied diet that is nutritionally appropriate for pregnancy, including foods rich in calcium, iron and folic acid. Your diet should be low in saturated fats and high in fibre. Carbohydrates such as grains, cereals, fruits, pasta and rice are an important part of your eating plan to provide you with energy and essential nutrients. You may need to discuss with a dietitian the amount and distribution of carbohydrate intake to help control your blood glucose levels
physical activity – such as walking, helps to keep you fit, prepares you for the birth of your baby and will help to control your blood glucose levels. Check with your doctor before starting a new or particularly strenuous exercise regimen
monitoring your blood glucose levels – is essential. It gives a guide as to whether the changes you have made to your lifestyle are effective or whether further treatment is required. A diabetes nurse educator can teach you how and when to measure your blood glucose levels and discuss the recommended blood glucose levels to aim for. Your doctor or diabetes educator can help you link in with the National Diabetes Services Scheme (NDSS) for cheaper blood glucose strips. Regular contact with your diabetes educator or doctor is recommended
insulin injections – may be needed to help keep your glucose level in the normal range. In Australia, blood glucose lowering tablets are generally not used in pregnancy. Insulin is safe to take during pregnancy and does not cross the placenta from the mother to the baby
education – including information and support from your diabetes educator or doctor, regarding the action of insulin, insulin injection technique, insulin storage, signs and symptoms of hypoglycaemia (low blood glucose levels) and its treatment, as well as safe blood glucose levels for driving.
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