Gestational Diabetes: What You Need to Know as a Patient

What is Gestational Diabetes?

Pregnant women who have high blood sugar (glucose) levels during pregnancy , but did not have diabetes before pregnancy are said to have gestational diabetes (GDM). The abnormally high blood sugar appears to be caused by hormones produced by the placenta that block the action of the mother's own insulin. Because insulin is required for sugar to enter cells, the sugar rises in her blood. Gestational diabetes usually develops in the second trimester as the placenta is getting larger. If your diabetes was diagnosed in the first half of your pregnancy, it's possible you had diabetes even before you conceived.

Testing for Diabetes

Your doctor may test you if he or she thinks you are at risk for developing GDM.  From 3% to 12% of all pregnancies are diagnosed with diabetes. 

Consequences of Diabetes

Women who are diabetic even when they are not pregnant are called pregestational diabetics. In pregestational diabetics fasting blood sugars persistently greater than 120 mg/dl in early pregnancy can cause miscarriage and birth defects. Mothers who are diabetic only when they are pregnant (GDM) do not have higher rates of birth defects, but may have a higher chance for a stillbirth if their sugars are not controlled well.

Later in pregnancy the excessive sugar in either type of diabetic crosses the placenta to the baby. The consequences are the baby grows, and grows, and grows. As the baby's size increases its risk for birth injuries with a vaginal delivery increases. These injuries may include a fractured collar bone, a fractured arm ,or paralysis of the upper arm.  Fortunately, these conditions are usually temporary. Very rarely, an infant may be so large it fails to deliver in a timely manner and suffers brain damage from prolonged lack of oxygen. If your doctor believes your baby is too large for you to safely attempt a vaginal delivery, he or she may recommend a cesarean delivery.

Babies born to mothers with poorly controlled diabetes are also at higher risk for low blood sugar , jaundice, polycythemia ( high numbers of red blood cells) , low calcium levels, and an increased risk for fetal death during the last months of pregnancy.

Lastly uncontrolled diabetes places the mother at risk for developing polyhydramnios (excessive amniotic fluid) and pre-eclampsia (high blood pressure with protein in the urine).


The first step in treatment is usually a change in diet. If you are diagnosed with GDM you may initially be instructed to:

  • Avoid sugars and sweets
  • Avoid instant foods.
  • Do not drink fruit juices
  • Eat 3 meals and snacks daily. Wait 2 to 3 hours between meals and snacks.
  • Do not eat fruit for breakfast. Eat fruit for snacks
  • Do not eat dry cereal (like cornflakes) for breakfast.
  • Eat more cooked or raw vegetables.

In addition a minimum of three episodes of exercise per week is also recommended. The sugar lowering effect of exercise may not be seen for 2 to 4 weeks.

If diet and exercise don't keep blood sugar controlled, then your doctor will likely prescribe insulin. If your blood sugar is only mildly elevated you may be offered an oral medication called glyburide. Approximately 15% to 20% of women with gestational diabetes will require insulin therapy. The major side effect of these medications is possible low blood sugar (hypoglycemia).

The Risk of Developing Diabetes Later in Life

Most women diagnosed with gestational diabetes may expect their blood sugars to return to normal after they have delivered. Whether a woman develops diabetes later in life seems to be predicted to some degree by her fasting blood sugar levels. If her fasting glucose levels during pregnancy are 105 to 130 mg/dl, 50% of mothers may be expected to become diabetic after pregnancy. 86 % of women with fasting blood sugars greater than 130 mg/dL may be expected to become diabetic.  It is recommended that  women with gestational diabetes be retested for diabetes six weeks after delivery. It is important that this follow up be done, so that women with diabetes may be effectively treated to avoid the harmful effects of neglected diabetes on the mother's health and her future pregnancies.

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