When a person becomes pregnant, they may develop a temporary form of diabetes called gestational diabetes mellitus (GDM). By some estimates, GDM occurs in about 10 percent of pregnancies in the United States and 16 percent worldwide. Gestational diabetes is becoming more common throughout the world, along with increased rates of obesity and rising maternal age.

If you do develop GDM, it’s important to be diagnosed and take necessary steps — eating a healthy diet, exercising, and possibly taking medications — so you can control your glucose (blood sugar) levels. This, in turn, can protect your health and that of your baby and prevent a difficult delivery.

Since GDM is fairly common in pregnancy, it’s important for an expecting parent to know about the condition, including the risks, signs and symptoms, and treatment options.

What Is Gestational Diabetes?

GDM is a temporary type of diabetes that a person may develop during pregnancy if they have no history of other types of diabetes (such as type 1 or type 2 diabetes mellitus). People are generally tested for the condition around the 24th and 28th weeks of gestation (pregnancy) or near the start of the third trimester. If you have a higher risk of gestational diabetes, your doctor may run tests earlier in pregnancy, possibly at your first prenatal visit.

What Is the Pathophysiology of Gestational Diabetes?

The pathophysiology of gestational diabetes — in other words, how this condition develops — is related to several factors.

GDM is a metabolic disorder that affects a person’s blood glucose levels (amount of sugar in the blood). It develops when a pregnant person’s body can’t make enough of the hormone insulin to keep up with their high energy demands or their growing baby’s. Insulin is made by beta cells within the pancreas.

Insulin signals cells to allow glucose from the blood to enter. Hormones from the placenta (an organ in the womb that connects the baby to the uterus by the umbilical cord) — such as human placental lactogen — can cause insulin resistance. Insulin resistance means that insulin is blocked or less effective at signaling to cells to absorb sugar from the blood. This happens mostly in the third trimester.

In most pregnancies, a person’s body naturally makes more insulin during the second and third trimester to overcome this extra need. However, for people with GDM, insulin resistance makes it difficult to use the hormone. For them, maintaining correct blood sugar levels can require up to three times more insulin. This is why some people may have GDM during pregnancy and not experience diabetes other times in their lives.

Symptoms of Gestational Diabetes

As with prediabetes (early diabetes), there aren’t many noticeable signs or symptoms associated with GDM, and they’re usually mild. Symptoms may include having to urinate more frequently or being more thirsty. This is why it’s important for a pregnant person to undergo routine tests.

Health Risks of Gestational Diabetes

GDM can affect pregnancy outcomes for both the baby and expecting parent. Maintaining healthy blood sugar levels is important to minimize these risks. Whether you’re experiencing hyperglycemia (high blood sugar levels) or hypoglycemia (low blood sugar levels), GDM can lead to serious or lifelong problems for the baby and the pregnant parent.

Risks to the Expecting Parent

GDM can lead to:

• Preeclampsia — This complication of pregnancy includes symptoms such as hypertension (high blood pressure) and proteinuria (high protein levels in the urine).
• Hypertension — High blood pressure can lead to other types of cardiovascular dysfunction (heart problems) later on in life.
• High risk for a required cesarean section (C-section) — C-section is a type of surgery to deliver a baby through an incision in the abdomen and uterus. This type of surgery poses some risks for the baby and parent.
• Increased risk of developing diabetes — According to the International Diabetes Federation, around 50 percent of women with GDM are diagnosed with type 2 diabetes within five to 10 years of giving birth.

Risks to the Baby

Babies born to a pregnancy that was stressed by GDM are at a greater risk of the following:

• Stillbirth or miscarriage
• Preterm (or premature) birth — Early delivery of the baby can result in complications including problems with the heart, brain, and immune system.
• Severe breathing problems, particularly those that are associated with preterm birth
• Macrosomia (high birth weight and size) — This occurs in 15 percent to 45 percent of newborns whose mothers have GDM. It’s defined as having a birth weight of 4,000 grams (about 8.8 pounds) or more.
• Low blood sugar
• Type 2 diabetes

GDM can also increase the risk of being overweight or having obesity later in life.

Who Is at Risk of Gestational Diabetes?

Many risk factors can contribute to your chances of having GDM. If you have any of these risk factors, it’s important to talk to your doctor so you can be tested earlier:

• Being overweight or having obesity before pregnancy — This is defined as having a body mass index (BMI) of 25 or higher.
• Having a gestational age (maternal age at birth) over 25 years
• Having a history of smoking
• Having a family history of diabetes
• Having sedentary lifestyle (mostly sitting or staying still) without healthy levels of physical activity before and during pregnancy
• Having prediabetes or a history of gestational diabetes
• Gaining weight too much or too fast during pregnancy
• Having polycystic ovary syndrome
• Having delivered a baby heavier than 9 pounds in a previous pregnancy
• Being a certain race or ethnicity, according to Mayo Clinic, including Black, Hispanic, American Indian, or Asian American

How Is Gestational Diabetes Diagnosed?

A doctor will perform a few types of tests during normal screening and if you are at risk of GDM. Typically, you’ll have different tests done to determine the amount of glucose that’s staying in your blood and not being used by your body.

Glucose Challenge Test

The first test is called the glucose challenge or glucose screening test. Your doctor will perform this test around 24 to 28 weeks of pregnancy — or earlier if you’re at risk of GDM. Your doctor will have you drink a specific sugary liquid that has a certain amount of glucose in it. You’ll then have your blood drawn around one hour later.

This test determines whether your body is producing the proper amount of insulin to keep your blood sugar at a normal level. If your blood test shows that your blood sugar is too high, your doctor may have you come back for additional testing. A result of 140 milligrams per deciliter (mg/dL) or more may be a sign of GDM. If your blood sugar is over 200 mg/dL, you may be tested for type 2 diabetes.

Oral Glucose Tolerance Test

The next test that a doctor will perform is called the oral glucose tolerance test (OGTT). However, if you are at a high risk of GDM, your doctor may decide to skip the glucose challenge test and start with the OGTT. The OGTT gives your doctor more accurate information about how your body is producing insulin in response to sugar because the test is performed while you are fasting. This means that you eat nothing and drink only water at least eight hours before the test.

The OGTT is similar to the glucose challenge test because you will be asked to drink a similar sugary liquid but your blood will be tested more than once. You will be asked to give a blood sample prior to drinking the liquid and after one hour, two hours, and three hours have passed. If you have multiple high readings, your doctor will most likely tell you that you have gestational diabetes and help you develop a treatment and management plan for the remainder of your pregnancy.

Managing Gestational Diabetes

Treating GDM includes making lifestyle changes, monitoring your blood sugar, and (if necessary) taking medications.

Maintaining a healthy diet is an important part of managing GDM. Eat plenty of fruits, vegetables, whole grains, and lean proteins — and avoid foods with highly refined carbohydrates, like desserts. A registered dietitian or diabetes specialist can help you develop a personalized meal plan.

Getting regular physical activity is also important because it can lower your blood sugar. Activities include exercises such as walking, cycling, and swimming, as well as day-to-day tasks like cleaning the house or gardening. Mayo Clinic recommends about 30 minutes of moderate physical activity most days or the week — but it’s important to follow guidance from your doctor and listen to your body.

Your health care team also may recommend checking your blood sugar levels several times a day to ensure they’re in a safe range. If diet and exercise don’t control your levels enough, your doctor may prescribe insulin injections or oral medications to manage them.

Once your pregnancy is over, you’ll need to be rechecked for diabetes after one to three months. It’s likely that your blood sugar will once again be under control, but you’ll need to be checked again every one to three years and continue healthy practices to maintain your weight and physical activity.

Talk With Your Doctor

If you’re at risk of gestational diabetes, be sure to have an open, in-depth conversation with your doctor about these risk factors. Share any concerns you have or symptoms you’re experiencing. If you’re unsure if you’re at risk, ask your doctor about issues that you are worried about and whether they may affect your pregnancy. Remember to keep up with your doctors’ appointments and get appropriate follow-up testing as directed.

Talk With Others Who Understand

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Are you living with gestational diabetes? Do you have questions about risks, symptoms, and treatment of GDM? Share your thoughts in the comments below, or start a conversation by posting on your Activities page.