GESTATIONAL DIABETES

Gestational diabetes occurs when a pregnant woman has high levels of glucose in her blood. High blood glucose is caused because the mother can’t produce enough insulin (a pregnant person’s insulin needs are two to three times that of normal).

There are two reasons why the mother needs more insulin:

  • Because pregnancy causes certain types of hormones (that are made by the placenta) to be released. These hormones make it harder for insulin to do its job

  • Because the growth demands of the foetus (developing baby) increases the mother’s need for insulin

Unlike type 1 and type 2 diabetes, gestational diabetes is only temporary and usually disappears after pregnancy. However, a person who has had gestational diabetes has an increased risk (50-60%) of developing type 2 diabetes in the future; therefore they should be tested for type 2 diabetes each year.

Why insulin is important

Insulin is a natural hormone produced by the body. It is needed to take the sugar from your blood and move it into your cells (where it is used as an energy source for the various things that cells have to do). If your body cannot make enough insulin, sugars from the foods you eat will stay in your blood stream and cause high blood sugars. High blood sugar levels are known as hyperglycaemia.

What are the complications associated with gestational diabetes?

During the pregnancy

  • 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 larger than average baby (weighing more than 4kg).

  • Premature birth (baby being born before 37 weeks) is more common.

  • Miscarriage (before 23 weeks) and stillbirth rates (baby dying before birth) are also higher.

  • An increased chance of getting urinary tract infections

  • Much higher risk of developing diabetes in the future.

The risks to your baby include:

At birth:

  • Being large at birth. Babies who are too large at birth have a much higher risk of developing serious problems following their birth.

  • Shoulder dystocia, which is a serious complication when the baby’s head passes through the vagina, but their shoulder gets stuck behind the mother's pelvic bone (the hips and ring of bone that supports your upper body).

  • Having a serious low blood glucose level soon after birth. This can happen because before being born your baby had been getting a very high level of glucose out of your blood (across the placenta). The baby had adjusted to this high glucose level by making high levels of its own insulin. When the placenta separates after birth this high level of glucose (from you) suddenly stops. The baby still has very high levels of its own insulin and this can cause its blood glucose to fall too low.

  • Prolonged new-born jaundice

  • Low levels of calcium in the blood

  • Respiratory distress syndrome (this can be quite dangerous)

Later in life:

  • Babies are at increased risk of developing diabetes or obesity (having a body mass index of more than 30) later in life.

Am I at risk of developing gestational diabetes?

If you have one or more of the following factors you are more likely to develop gestational diabetes:

  • Having a family history of type 2 diabetes in a close relative (parents or brothers and sisters)

  • Having gestational diabetes in a previous pregnancy

  • If a previous baby had a birth defect

  • If you are very overweight

  • If you are aged over 30

  • If you have had a previous stillbirth or spontaneous miscarriage

  • If you’ve had a previous large baby (greater than 4 kilos)

  • If you have a history of pregnancy-induced high blood pressure, urinary tract infections, or polyhydramnious (too much amniotic fluid)

Screening for gestational diabetes

Every pregnant woman should now be offered a blood test for glycated haemoglobin (HbA1c), as a routine part of booking antenatal blood tests before 20 weeks. This will help identify women with probable undiagnosed diabetes or prediabetes and will help to identify women at high risk of developing gestational diabetes.

At 24–28 weeks of pregnancy, you will be offered a further blood test to check for any diabetes.

The screening test is called an oral glucose tolerance test (OGTT), which takes about 2 hours.

It involves having a blood test in the morning, when you have not had any food or drink for 8 to 10 hours (though you can usually drink water, but check with the hospital if you're unsure). You're then given a glucose drink. 

After resting for 1-2 hours, another blood sample is taken to see how your body is dealing with the glucose.

  • For women whose earlier HbA1c was 41–49 mmol/mol at booking, a two-hour glucose tolerance test (GTT) is organised.

  • For women whose HbA1c was normal, a one-hour, 50 g oral glucose challenge test (polycose) is done.

Treatment for gestational diabetes

In most cases, gestational diabetes is able to be managed by diet and exercise during the pregnancy. It usually disappears after the baby is born once the need for high levels of insulin (during pregnancy) has gone.

Some women with gestational diabetes require insulin to manage their blood sugar levels in a healthy range during the pregnancy. If you do need insulin, it will help to keep both you and your baby healthy during the pregnancy.

It is very much better for both you and your baby to be in the care of a specialist team if you have been diagnosed with gestational diabetes. This team can help you to learn the skills you need to know to manage your gestational diabetes.

You will most probably want to talk over each of the following issues with your health care team members:

  • Keeping your blood glucose levels in a healthy range.

  • Using a home blood glucose meter to test your blood glucose levels. Whether you need to do this testing and if so how often, will depend on the results of your laboratory blood glucose levels.

  • Managing your weight gain during pregnancy. But remember that good nutrition is important during pregnancy. A dietitian will help you work out your nutritional needs.

  • A healthy level of exercise (exercise helps improve blood glucose levels for some people, and is important to improve flexibility and prepare you for childbirth)

  • Breastfeeding. There isn’t any reason why you shouldn’t breastfeed baby. Your milk is the best source of food for your baby.

Remember, if you have had gestational diabetes you should be checked for type 2 diabetes every year for the rest of your life. Your best defence against developing type 2 diabetes is to try to keep your body weight lean and get plenty of physical exercise. Some people remember this by ‘staying lean and mean’.