03 Aug 2010

Diabetes In pregnancy – Gestational Diabetes Mellitus (GDM)

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Approximately 5% of pregnant women will develop Gestational Diabetes Mellitus (GDM) during their pregnancy. Left untreated, GDM may cause problems during the pregnancy, or for the baby. The diabetes usually goes away once the baby is born.

What is diabetes?

  • The term diabetes means too much sugar (glucose) in the blood. The body relies upon glucose for energy and glucose crosses the placenta and is the baby’s primary nutrient.
  • The body makes glucose from certain carbohydrate foods such as cereal foods (bread rice and pasta), fruit and milk and some vegetables (potato corn).
  • The sugar is carried around the body by the blood system and must stay at a level which is not too high, nor too low.
  • To move from the blood and into the tissues where it is needed, the body relies upon a small gland called the pancreas producing a hormone called insulin.
  • Insulin allows glucose in the blood to enter the body cells. Without insulin, the glucose rises in the blood and diabetes occurs.

Why do I have GDM?

During pregnancy the body undergoes many changes to provide the best conditions for the growing baby.

  • The placenta makes hormones some of which cause the body tissues to become resistant to insulin.
  • The pancreas has to produce extra insulin to overcome this resistance.
  • Inability of the pancreas to produce this extra insulin causes gestational diabetes to develop.

Why wasn’t I tested earlier than 28 weeks?

It is possible that your diabetes could have been diagnosed earlier, but few women develop GDM before 28 weeks. The last 12 weeks of the pregnancy is when GDM is most commonly found. Controlling the blood glucose levels at this time is helpful in preventing the possible risks to the baby.

We occasionally test women for GDM at 13 weeks gestation. These women are usually those who previously had a previous pregnancy affected by GDM or are otherwise at high risk of developing diabetes.

Why me?

There are certain risk factors which may contribute to the diagnosis. These risk factors include:

  • Maternal age greater than 35 years.
  • A family history of diabetes.
  • Previous pregnancy diabetes.
  • Multiple pregnancy.
  • Ethnicity – certain races are more susceptible to diabetes.
  • A history of having large babies (over 4.5 kgs).
  • A condition known as Polycystic Ovarian Syndrome or PCOS.
  • Increased maternal weight

Occasionally, there are no obvious risk factors for developing GDM, which is why screening is recommended for all pregnant women.

Does my baby have Diabetes?

There is no risk of your baby being born with diabetes as a result of having Gestational Diabetes however there are possible risks to the baby which is why treatment is important.

What are the risks to my baby?

The aim of treatment is to minimise risks to your baby. Learning how to control your blood glucose levels will greatly minimize these risks. Possible risks include:

  • The baby becoming overweight during the pregnancy, which may increase the need for an instrumental delivery or Caesarean section.
  • The baby may have some low blood sugar levels shortly after the birth.
  • Babies who are born to mothers with undiagnosed GDM or poorly controlled blood sugars are at risk of obesity in childhood. This will then increase their future risks of developing Diabetes in the future.
  • Congenital abnormalities are not usually associated with Gestational Diabetes.

What treatment do I need?

  • Most women will control their Gestational Diabetes by exercising and following a carefully prescribed diet.
  • A small percentage of women will need additional insulin to keep the blood sugar levels under control.
  • You will be required to test your blood sugars at home.
  • You will be required to see a specialist physician, a midwife with expertise in diabetes management and your obstetrician to monitor the Diabetes (we’re a team!).
  • You will have one or two formal ultrasound scans in order to careful monitor your baby’s growth and welfare before the birth.

Will my birth be affected?

  • In general you will have the type of birth that you planned on as long as your baby does not grow unusually large during your pregnancy. Having an unduly big baby is extremely rare if GDM is diagnosed and managed appropriately
  • That said we sometimes advise you not to go over your due date. This advice is usually given if you need to take insulin to manage your diabetes or we are concerned about your sugar levels or your baby seems quite large. Accordingly we wind up inducing labour more often in women with GDM than in women without any pregnancy complications.

Will my baby go to a special care nursery?

  • It is not routine procedure to send the baby to special care.
  • Your baby will have his or her blood sugar tested to make sure it’s blood sugars are within the normal range. This is performed by a simple heel prick.

Can I still breastfeed?

  • You have the right to chose how you feed your baby. Breast milk has been shown to help prevent obesity and diabetes.

Will the Diabetes go away once the baby is born?

  • In most cases Gestational Diabetes will disappear once the baby is born, however it does highlight a future risk for Type 2 Diabetes.
    • Follow up testing is recommended at 6 weeks after the birth and then every 2 years thereafter.

Don’t Panic!

If diagnosed and managed appropriately GDM should have very little effect on your pregnancy and birth. The health of you and your baby should not be affected by GDM.

This information sheet was prepared by my midwifery colleague Amanda Bartlett. Amanda is the specialist midwife to whom I will refer you if you develop GDM


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