Gestational Diabetes

GDM is a condition diagnosed in pregnant women when higher than normal blood sugar levels first appears during pregnancy. About 5% (1in 20) pregnant women may develop GDM usually around 24th to 28th week of pregnancy, however in some it may be earlier. It is important to recognise and treat gestational diabetes as soon as possible to minimize the risk of complications in the baby.

The factors that can put you at a higher risk of developing GDM include if you:
Have a family history of Type 2 Diabetes

  • Are overweight
  • Had GDM in previous pregnancy
  • Are over the age of 30
  • had previous adverse pregnancy outcomes
  • Are from a Indian, Vietnamese, Chinese, Middle Eastern, Polynesian/ Melanesian background
  • Are indigenous Australian or Torres Strait islander background
  • Have glucose in the urine
  • Have a twin (Multiple) pregnancy

What causes GDM?

During pregnancy placenta produces several hormones that help the baby grow and develop. These hormones also block the action of mother’s insulin. Because of this insulin resistance in mother’s body from placental hormones, the need for insulin is 2-3 times higher in pregnancy. If the body is unable to produce this much insulin, then GDM develops. When the pregnancy is over the insulin needs also return to normal, the diabetes usually disappears.

GDM testing:

We recommend that all pregnant women be screened for GDM. Screening test is usually done between 24 and 28 weeks of pregnancy or occasionally earlier if you have any of strong risk factors.

Screening test: On the day of test you can eat and drink normally. You will be given a specially formulated lemonade type of drink containing 50 grams of glucose. You should drink the whole amount within a few minutes. One hour later you will have a blood test to measure your blood sugar level. If your blood sugar level is higher than normal ( 7.8 mmol/L) you will need another test to know for sure if you have GDM.

The confirmatory test is oral glucose tolerance test. Eat a normal diet containing atleast 300 grams of carbohydrates for three days before the test. The test is performed after 8 hours of fasting for food and fluids. A fasting venous blood is collected. Then you will be given a 75 gram glucose drink that you should drink within few minutes, and you have to remain seated and non-smoking. Measurement of blood sugar level is done at one hour and at two hours. A fasting glucose ? 5.5 mmol / L or a glucose 8 mmol/L at two hours after the drink indicates the need for dietary advice and home blood sugar monitoring.

GDM Treatment:

The management and treatment of GDM is a team effort involving you and your partner, your doctor with specialists, dietician and diabetes educator. The main components that effectively treat GDM involve changing your eating pattern, physical activity and blood sugar monitoring.

Most women with gestational diabetes manage their condition by changing their diet. A few women require insulin injections if their new diet is unable to keep the blood sugar levels within normal limits. Occasionally, the woman may require admission in the hospital if blood sugar levels are high despite monitoring and treatment and when compliance with diet and treatment is an issue.


The main health risk for pregnant women with uncontrolled gestational diabetes is producing an abnormally large baby (over 4.5 kg or about 10lb), called fetal macrosomia or large for gestational age (LGA). A large baby can be hard to deliver through the pelvis (shoulder dystocia). This increases the risk of injury to the baby (bone and nerve injury). Also there is a higher risk of injury to the perineum and other soft tissues of the mother during birth. Some women may require caesarean delivery if the baby is too big. You are more likely to have a large baby if your blood sugar levels are higher than normal during pregnancy.

Babies of diabetic women are not born with diabetes. However, due to a genetic inheritance, they may also be at a slightly increased risk of developing diabetes later in their life. There is also a risk of baby dying inside the womb if blood sugar levels are not in control. Most babies are healthy at birth if your blood sugar levels are kept within limits during pregnancy. A small percentage of babies will need close observation requiring admission to special care nursery. These problems may include: low blood sugar level, low blood calcium and magnesium levels, neonatal jaundice, breathing problems and excess red blood cells.

After Pregnancy:

The blood sugar levels return to normal after the delivery. An oral glucose tolerance test will be performed at 6 weeks after the birth and will usually be normal. However there is an increased risk of you developing type 2 diabetes later in life with a 30 to 50% chance of developing it within 15 years after your pregnancy. There are some positive steps you can take to help delay or even prevent the development of type 2 diabetes. It is important to: Continue eating healthy, being physically active, Keep your weight within ideal weight range and have your blood glucose level checked once every 2-3 years.

Further Resource:

Download: Understanding Gestational Diabetes Booklet (English/Turkish version) from Patient Information – Gestational Diabetes ()

For more information you can contact Diabetes Australia on 1300 136 588.