Diabetes of Pregnancy - Gestational Diabetes

Overview, Causes, & Risk Factors

Gestational diabetes is an intolerance to glucose that first occurs, or is first detected, during pregnancy. Glucose is the main form of sugar in the body. Gestational diabetes occurs in 4% of all pregnancies.

What is going on in the body?

Glucose is an important source of energy used by the body's cells. When a person eats, the pancreas normally makes extra insulin. The insulin causes the glucose in the blood to move inside the body's cells. In a woman with gestational diabetes, the hormones produced in pregnancy block the effects of insulin. Glucose then builds up in the blood and the cells are left without a main source of energy. The result is a high level of glucose in the blood, a condition known as hyperglycemia. High blood sugar levels can damage the growth of the fetus. This may cause complications for both the mother and baby.

What are the causes and risks of the disease?

The following conditions may increase a woman's chance of developing gestational diabetes:

age over 25 years

family history of diabetes mellitus, including type 1 diabetes mellitus or type 2 diabetes mellitus in a sibling or parent

personal history of gestational diabetes

marked obesity

previous delivery of an infant with a birth weight of more than 9 pounds

a previous stillbirth

previous delivery of a child with birth defects

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glucose in the urine sample taken in the healthcare provider's office

being a member of an ethnic group with a high incidence of gestational diabetes. This includes women of Latino, African American, Native American, Asian, or Pacific Islands descent.

Symptoms & Signs

What are the signs and symptoms of the disease?

Usually there are no symptoms of gestational diabetes. If symptoms develop, they are often mild and may include:

excessive thirst

excessive weight gain or sometimes excessive weight loss despite increased appetite

increased urination

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fatigue

nausea

vomiting

blurred vision

recurrent or persistent bladder infections or bacteria in the urine

Diagnosis & Tests

How is the disease diagnosed?

The American Diabetes Association (ADA) recommends glucose testing of women with any of the risk factors listed above as soon as feasible during pregnancy. If gestational diabetes is not diagnosed during the initial screening of high risk women, they should be retested between 24 and 28 weeks of pregnancy. Similarly, women of average risk should be tested between 24 and 28 weeks of pregnancy.

The ADA describes 2 approaches to evaluation of gestational diabetes in pregnant women:

The one-step approach is done with an oral glucose tolerance test. The woman drinks a liquid containing 50 grams of glucose and the blood glucose level is measured an hour later.

The two-step approach starts with the same oral glucose tolerance test as the one-step approach. If the woman's blood glucose is elevated on the first test, a diagnostic oral glucose tolerance test is done. The woman drinks a liquid containing 100 grams of glucose, and the blood glucose level is measured 1, 2, and 3 hours later.

If the blood glucose level is elevated in either of the approaches, a diagnosis of gestational diabetes is made.

Prevention & Expectations

What can be done to prevent the disease?

Gestational diabetes can sometimes be prevented by regular exercise and a balanced diet to maintain a healthy weight before conceiving and during pregnancy. It is important to let the healthcare provider know if there is a family history of diabetes.

What are the long-term effects of the disease?

Complications for the mother include:

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higher risk of preeclampsia, or very high blood pressure

swelling in the arms and legs as a result of fluid buildup

carpal tunnel syndrome, or pain and numbness involving the hand and arm

premature labor

increased need for medication to induce labor

increased risk of forceps delivery or cesarean section

What are the risks to others?

Complications for the baby include:

macrosomia, which means having a large body

polyhydramnios, or excessive amniotic fluid

increased incidence of birth defects

premature delivery

increased risk of miscarriage

hypoglycemia, or low blood sugar levels at birth

hypocalcemia, or low calcium levels at birth

polycythemia, or too many red blood cells at birth

respiratory problems, including respiratory distress syndrome

cardiomyopathy, or damaged heart tissue

congestive heart failure

increased risk of birth trauma such as shoulder dystocia, which occurs when the baby's shoulder gets stuck during delivery

decreased ability of the baby to tolerate labor

Treatment & Monitoring

What are the treatments for the disease?

The goal of treatment is to bring blood glucose levels to normal, and to keep them there throughout the pregnancy. This will prevent complications for both mother and child. The diet should provide enough calories and nutrients to allow appropriate weight gain in both mother and fetus. A dietician will provide counseling and education. If changing the diet does not control glucose levels, insulin injections may be needed.

Until recently, oral medications were not recommended for gestational diabetes. However, a recent study indicated that glyburide is safe and effective to take in the last 6 months of pregnancy.

What are the side effects of the treatments?

Hypoglycemia, or low blood sugar, may result if too much insulin is given, or if meals are skipped. Hypoglycemia should be avoided, because the fetus will also experience low blood sugar levels.

What happens after treatment for the disease?

Pregnancy hormones drop dramatically after delivery, and a woman may no longer need insulin. High blood glucose levels usually go away after pregnancy. But 30% to 40% of women with gestational diabetes may develop type 2 diabetes at some time in their lives. Obesity or a family history of diabetes may increase this risk. A balanced diet and exercise after delivery will help with weight loss and will lower the risk of diabetes in the future. At the exam 6 weeks after delivery, a oral glucose tolerance test can help determine if further treatment is needed.

How is the disease monitored?

Women with gestational diabetes run a high risk of having it in future pregnancies. Women who previously had gestational diabetes but are not pregnant should have fasting blood sugar tests each year to detect diabetes.