During pregnancy, some women develop high blood sugar levels. This condition is known as gestational diabetes mellitus (GDM) or gestational diabetes. Gestational diabetes typically develops between the 24th and 28th weeks of pregnancy.
According to the Centers for Disease Control and Prevention, it’s estimated to occur in 2 to 10 percent of pregnancies in the United States.
If you develop gestational diabetes while you’re pregnant, it doesn’t mean that you had diabetes before your pregnancy or will have it afterward. But gestational diabetes does raise your risk of developing type 2 diabetes in the future.
It’s rare for gestational diabetes to cause symptoms. If you do experience symptoms, they’ll likely be mild. They may include:
The exact cause of gestational diabetes is unknown, but hormones likely play a role. When you’re pregnant, your body produces larger amounts of some hormones, including:
- human placental lactogen (hPL)
- hormones that increase insulin resistance
These hormones affect your placenta and help sustain your pregnancy. Over time, the amount of these hormones in your body increases. They may start to make your body resistant to insulin, the hormone that regulates your blood sugar.
Insulin helps move glucose out of your blood into your cells, where it’s used for energy. In pregnancy, your body naturally becomes slightly insulin resistant, so that more glucose is available in your blood stream to be passed to the baby. If the insulin resistance becomes too strong, your blood glucose levels may rise abnormally. This can cause gestational diabetes.
You’re at a higher risk of developing gestational diabetes if you:
- are over the age of 25
- have high blood pressure
- have a family history of diabetes
- were overweight before you became pregnant
- gain a larger than normal amount of weight while you’re pregnant
- are expecting multiple babies
- have previously given birth to a baby weighing more than 9 pounds
- have had gestational diabetes in the past
- have had an unexplained miscarriage or stillbirth
- have been on glucocorticoids
- have polycystic ovary syndrome (PCOS), acanthosis nigricans, or other conditions that are associated with insulin resistance
- have African, Native American, Asian, Pacific Islander, or Hispanic ancestry
The American Diabetes Association (ADA) encourages doctors to routinely screen pregnant women for signs of gestational diabetes. If you have no known history of diabetes and normal blood sugar levels at the beginning of your pregnancy, your doctor will likely screen you for gestational diabetes when you’re 24 to 28 weeks pregnant.
Glucose challenge test
Some doctors may begin with a glucose challenge test. No preparation is needed for this test.
You’ll drink a glucose solution. After one hour, you’ll receive a blood test. If your blood sugar level is high, your doctor may perform a three-hour oral glucose tolerance test. This is considered two-step testing.
Some doctors skip the glucose challenge test altogether and only perform a two-hour glucose tolerance test. This is considered one-step testing.
- Your doctor will start by testing your fasting blood sugar levels.
- They’ll ask you to drink a solution containing 75 grams (g) of carbohydrates.
- They’ll test your blood sugar levels again after one hour and two hours.
They’ll likely diagnose you with gestational diabetes if you have any of the following
- fasting blood sugar level greater than or equal to 92 milligrams per deciliter (mg/dL)
- one-hour blood sugar level greater than or equal to 180 mg/dL
- two-hour blood sugar level greater than or equal to 153 mg/dL
- For the two-step test, you will not need to be fasting.
- They’ll ask you to drink a solution containing 50 g of sugar.
- They’ll test your blood sugar after one hour.
If at that point your blood sugar level is greater than or equal to 130 mg/dL or 140 mg/dL, they’ll conduct a second follow-up test on a different day. The threshold for determining this is decided by your doctor.
- During the second test, your doctor will start by testing your fasting blood sugar level.
- They’ll ask you to drink a solution with 100 g of sugar in it.
- They’ll test your blood sugar one, two, and three hours later.
They’ll likely diagnose you with gestational diabetes if you have at least two of the following values:
- fasting blood sugar level greater than or equal to 95 mg/dL or 105 mg/dL
- one-hour blood sugar level greater than or equal to 180 mg/dL or 190 mg/dL
- two-hour blood sugar level greater than or equal to 155 mg/dL or 165 mg/dL
- three-hour blood sugar level greater than or equal to 140 mg/dL or 145 mg/dL
The ADA also encourages doctors to screen women for type 2 diabetes at the beginning of pregnancy. If you have risk factors for type 2 diabetes, your doctor will likely test you for the condition at your first prenatal visit.
These risks factors include:
- being overweight
- being sedentary
- having high blood pressure
- having low levels of good (HDL) cholesterol in your blood
- having high levels of triglycerides in your blood
- having a family history of diabetes
- having a past history of gestational diabetes, prediabetes, or signs of insulin resistance
- having previously given birth to a baby who weighed more than 9 pounds
- being of African, Native American, Asian, Pacific Islander, or Hispanic descent
Gestational diabetes is divided into two classes.
Class A1 is used to describe gestational diabetes that can be controlled through diet alone. People with class A2 gestational diabetes will need insulin or oral medications to control their condition.
If you’re diagnosed with gestational diabetes, your treatment plan will depend on your blood sugar levels throughout the day.
In most cases, your doctor will advise you to test your blood sugar before and after meals, and manage your condition by eating healthy and exercising regularly.
They may also prescribe insulin injections for you until you give birth. Ask your doctor about properly timing your insulin injections in relation to your meals and exercise to avoid low blood sugar.
Your doctor can also tell you what to do if your blood sugar levels fall too low or are consistently higher than they should be.
A balanced diet is key to properly managing gestational diabetes. In particular, women with gestational diabetes should pay special attention to their carbohydrate, protein, and fat intake.
Eating regularly — as often as every two hours — can also help you to control your blood sugar levels.
Carbohydrates should account for only 40 to 50 percent of your calories each day. Aim to get 20 to 25 percent of your calories from protein and 25 to 35 percent of your calories from fat.
Pregnant women should aim for a daily total of 120 to 195 g of carbohydrates. This should be spread out across roughly 3 meals and 2 snacks each day. Properly spacing out carbohydrate-rich foods will help to prevent blood sugar spikes.
Your doctor will help you determine exactly how many carbohydrates you should eat each day. They may also recommend that you see a registered dietician to help with meal plans.
Healthy carbohydrate choices include:
Healthy fats to incorporate into your diet include unsalted nuts, seeds, olive oil, and avocado. Get more tips here on what to eat — and avoid — if you have gestational diabetes.
If your gestational diabetes is poorly managed, your blood sugar levels may remain higher than they should be throughout your pregnancy. This can lead to complications and affect the health of your child. For example, when your baby is born, he or she may have:
- a high birth weight
- breathing difficulties
- low blood sugar
- shoulder dystocia, which causes their shoulders to get stuck in the birth canal during labor
They may also be at higher risk of developing diabetes later in life. That’s why it’s so important to take steps to manage your gestational diabetes by following your doctor’s recommended treatment plan.
Your blood sugar should return to normal after you give birth. But developing gestational diabetes raises your risk of type 2 diabetes later in life. Ask your doctor how you can lower your risk of developing these conditions and associated complications.
It’s not possible to prevent gestational diabetes entirely. However, adopting healthy habits can reduce your chances of developing the condition.
If you’re planning to become pregnant in the near future and you’re overweight, one of the best things you can do is work with your doctor to lose weight. Even losing a small amount of weight can help you reduce your risk of gestational diabetes.