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Gestational Diabetes

Gestational diabetes is a type of diabetes that develops in some women when they are pregnant. Like other types of diabetes, gestational diabetes affects how cells use glucose (sugar), resulting in high blood sugar. However, in gestational diabetes, high blood glucose levels can affect your pregnancy and your baby’s health.1,2

Gestational diabetes affects nearly 10 percent of pregnancies in the United States each year. Some women have more than 1 pregnancy that is affected by gestational diabetes. This type of diabetes usually goes away after the baby is born. However, about 50 percent of women with gestational diabetes go on to develop type 2 diabetes.1,2

Understanding gestational diabetes and how to control your blood glucose levels during pregnancy can keep you and your baby healthy and prevent a complicated delivery.

What causes gestational diabetes?

Doctors do not know exactly what causes gestational diabetes, but they think hormones play a big role. During pregnancy, hormone levels change and make it harder for your body to make and use the insulin it needs. This is a hormone that your body uses to help glucose (sugar) get into cells so it can be used for energy. When your body becomes resistant to insulin or does not make enough, it causes your blood glucose levels to rise.2

Who should be screened for gestational diabetes and when should screening occur?

Women who have not previously been diagnosed with diabetes are usually screened for gestational diabetes between 24 and 28 weeks of pregnancy.1-3

If you are at high risk of diabetes, your doctor might screen you early in your pregnancy – likely at your first prenatal visit. Risk factors for diabetes include:3

  • Being overweight or obese
  • Lack of physical activity
  • A history of gestational diabetes or prediabetes
  • Polycystic ovary syndrome (PCOS)
  • Family history of type 2 diabetes
  • Previously giving birth to a baby weighing more than 9 lbs

Additionally, women who have been diagnosed with gestational diabetes should have their blood glucose level checked 6 to 12 weeks after delivery. Women with a history of gestational diabetes should be screened for diabetes and prediabetes every 3 years.3

How is gestational diabetes diagnosed?

Gestational diabetes is screened for using an oral glucose tolerance test (OGTT). This is a blood test that checks your blood sugar levels before and after you drink a sweet drink that contains glucose (sugar). The test, which is also known as the glucose tolerance test, measures how your body responds to sugar.

1-hour oral glucose tolerance test

Most women first take the 1-hour test. This is usually done between 24 and 28 weeks of pregnancy. If you are at risk for gestational diabetes, your doctor may perform the OGTT sooner.4

  • You will drink about 8 ounces of a sweet glucose drink that has 2.6 ounces (75 grams) of sugar
  • 1 hour after finishing the drink, your blood glucose level will be measured again

3-hour oral glucose tolerance test

If you are at risk for gestational diabetes or have high blood sugar levels after the 1-hour test, your doctor may have you take the 3-hour OGTT. For that test, you will need to fast and provide another blood sample. After that:4

  • You will drink about 8 ounces of a sweet glucose drink that has 3.5 ounces (100 grams) of sugar
  • Your blood glucose level will be tested 1, 2, and 3 hours after finishing the drink

The American Diabetes Association uses the following OGTT blood glucose levels to diagnose gestational diabetes:2

  • 95 mg/dL or higher after fasting
  • 180 mg/DL or higher 1 hour after the glucose drink
  • 155 mg/dL or higher 2 hours after the glucose drink
  • 140 mg/dL or higher 3 hours after the glucose drink

If 1 of your test results is above normal, your doctor will probably retest you in 4 weeks. If 2 or more of your test results are above normal, you will be diagnosed with gestational diabetes. Talk to your doctor about how you can manage your blood glucose levels throughout your pregnancy.2

Can gestational diabetes result in pregnancy complications?

Gestational diabetes that is not well controlled can cause health problems for both the mother and baby. These include:1

  • High birth weight (greater than 9 lbs) – Blood glucose levels that are not well controlled in the mother causes the baby’s levels to also be high. This causes the baby to grow extra large, which poses increased risk of injury to the mother and baby during birth and increases the likelihood of cesarean section (C-section). This is an operation to deliver the baby through an incision in the mother’s abdomen and uterus.
  • High blood pressure (preeclampsia) – This is a condition characterized by elevated blood pressure, increased protein in the urine, and often swelling that does not go away. This is a serious problem that can cause harm to both the woman and baby, including premature birth, or seizures or a stroke in the mother.
  • Low blood sugar (hypoglycemia) – If the mother’s diabetes was not well controlled during pregnancy, her baby can quickly develop low blood sugar after birth. Doctors must closely monitor the baby’s blood sugar for several hours after birth.

A number of studies have also found that children of mothers who had gestational diabetes have an increased risk for becoming obese, as well as eventually developing type 2 diabetes.5

How is gestational diabetes treated?

The goal of treatment in gestational diabetes is to control your blood glucose levels. Depending on your care plan, the may include:2,6

  • Special meal plans
  • Regular physical activity
  • Daily blood sugar testing
  • Insulin injections

In most cases, doctors recommend the following blood sugar levels during pregnancy:2,6

  • Before a meal – 95 mg/dL or less
  • 1 hour after a meal – 140 mg/dL or less
  • 2 hours after a meal – 120 mg/dL or less

If you have already been diagnosed with type 2 diabetes before becoming pregnant, your daily blood sugar level targets may be different. In most cases, doctors recommend the following targets:7

  • Before a meal – 90 mg/dL or less
  • 1 hour after a meal – 130 to 140 mg/dL or less
  • 2 hours after a meal – 120 mg/dL or less
  • A1C – 6 percent or lower after the first 3 months of pregnancy

Whether you are newly diagnosed with gestational diabetes or you have type 2 diabetes and are pregnant, you should talk to your doctor about what blood sugar levels are right for you.

More on this topic

Regular visits with your healthcare team will also help you and your baby get the best care. Your team may include:7

  • An obstetrician/gynecologist
  • A medical doctor who specializes in diabetes care (endocrinologist)
  • A nurse practitioner who provides prenatal care
  • A diabetes educator who helps you manage your diabetes
  • A registered dietitian who helps you with nutrition goals and meal planning

With this help, you can have a healthy pregnancy and a healthy start for your baby.

Can gestational diabetes be prevented?

As with type 2 diabetes, gestational diabetes can be prevented by maintaining a healthy body weight. In addition, getting regular physical activity may help prevent it from developing during pregnancy.2,6

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Written by: Jonathan Simmons & Heather Morse | Last reviewed: October 2020.