During pregnancy, some women develop high blood sugar levels. This condition is known as gestational diabetes mellitus (GDM). GDM 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 up to 9.2 percent of pregnancies.
If you develop GDM while you’re pregnant, it doesn’t mean that you had diabetes before your pregnancy or will have it afterward. But GDM does raise your risk of developing type 2 diabetes in the future. If poorly managed, it can also raise your child’s risk of developing diabetes and add other risk factors to you and your baby during pregnancy and delivery.
It’s rare for GDM to cause symptoms. If you do experience symptoms, they will likely be mild. They may include:
- blurred vision
- excessive thirst
- excessive need to urinate
The exact cause of GDM is unknown, but hormones likely play a role. When you’re pregnant, your body produces larger amounts of some hormones, including:
- human placental lactogen
- 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 interfere with the action of insulin, the hormone that regulates your blood sugar.
Insulin helps move glucose out of your blood into cells, where it’s used for energy. If you don’t have enough insulin, or you have high levels of hormones that prevent insulin from working properly, your blood glucose levels may rise. This can cause GDM.
You’re at higher risk of developing GDM if you:
- are over the age of 25
- have high blood pressure
- have a family history of diabetes
- were overweight before you became pregnant
- have previously given birth to a baby weighing more than 9 pounds
- have had an unexplained miscarriage or stillbirth
- are a high risk ethnicity
The American Diabetes Association encourages doctors to routinely screen pregnant women for signs of GDM. 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 GDM when you’re 24 to 28 weeks pregnant. They will conduct either a one-step or a two-step oral glucose tolerance test.
For the one-step test, your doctor will start by testing your fasting blood sugar levels. Then they will ask you to drink a solution containing 75 grams of carbohydrates. Then they will test your blood sugar levels again after one hour and two hours. They will likely diagnose you with GDM if you have any of the following blood sugar values:
- fasting blood sugar level greater than or equal to 92 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, your doctor will start by testing your fasting blood sugar level. Then they will ask you to drink a solution containing 50 grams of sugar. They will test your blood sugar again after one hour. If at that point your blood sugar level is greater than or equal to 140 mg/dL, they will conduct a second follow-up test on a different day.
During the second test, your doctor will start again by testing your fasting blood sugar level. Then they will ask you to drink a solution with 100 grams of sugar in it. Then they will test your blood sugar one, two, and tree hours later. They will likely diagnose you with GDM 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 American Diabetes Association 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 GDM, prediabetes, or signs of insulin resistance
- having a past of history of giving birth to a baby who weighed more than 9 pounds
- being of African, Latino, Asian, Native American, or Pacific Islander descent
If you’re diagnosed with GDM, 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. In some cases, they may also add insulin injections if needed.
If your doctor encourages you to monitor your blood sugar levels, they may supply you with a special glucose-monitoring device. 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 do if your blood sugar levels fall too low or are consistently higher than they should be.
If your GDM 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 they’re born, your baby may have:
- a high birth weight
- breathing difficulties
- low blood sugar
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 GDM by following your doctor’s recommended treatment plan.
Your blood sugar should return to normal after you give birth. But developing GDM 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.