Gestational diabetes is a kind of diabetes that affects pregnant women. Here's what you need to know about normal blood sugar levels during pregnancy.

Gestational diabetes is a type of diabetes that affects some pregnant women. It causes persistently high blood sugar levels, which can harm the health of both the mom-to-be and the fetus. The good news is there are a number of ways to manage this condition and avoid health complications.

Normal Blood Sugar Levels During Pregnancy

Blood sugar level goals for women with gestational diabetes are the same as those for people with type 1 or type 2 diabetes, Elizabeth Halprin, MD, clinical director of adult diabetes at Harvard's Joslin Diabetes Center, tells 1. "Blood sugar levels should be less than 95 mg/dL fasting [i.e., before breakfast] and less than 130 mg/dL one hour post-meal," Dr. Halprin says.

The prevalence of gestational diabetes has increased in the U.S., according to the American Diabetes Association's (ADA's) Standards of Medical Care in Diabetes—2019. This increase corresponds with the rise of obesity in the U.S 12. Though being overweight won't necessarily lead to gestational diabetes, it is a major risk factor.

During pregnancy, the placenta (which connects the fetus to the mother's blood supply) releases hormones that impair insulin action. Insulin is the hormone in charge of maintaining normal glucose (blood sugar) levels. As the fetus grows, so does the placenta, meaning more and more insulin-counteracting hormones are released as the pregnancy progresses 3. This may be why gestational diabetes typically doesn't occur until at least 20 weeks into a pregnancy 3. It's currently unclear, however, why some women develop gestational diabetes but other women don't, according to Cedars-Sinai Medical Center 13.

Read more: What Is a Healthy Blood Sugar Level Reading in the Morning?

What Gestational Diabetes Test Numbers Really Mean

Gestational diabetes levels are tested by analyzing the amount of glucose in a small drop of your blood, according to the Centers for Disease Control and Prevention (CDC) 3. But unless you already have type 1 or type 2 diabetes when you become pregnant, it's unlikely that you'll be monitoring your blood sugars if you haven't received a gestational diabetes diagnosis. This is why screening for gestational diabetes is so important.

Gestational diabetes is diagnosed when the amount of glucose in the blood exceeds certain levels before or after an oral glucose-tolerance test 5. Most pregnant women are screened for gestational diabetes between weeks 24 and 28 weeks of their pregnancy, according to the U.S. National Library of Medicine 34.

There are several types of oral glucose-tolerance tests 5. They all involve measuring fasting blood sugar levels, drinking a very sugary drink and then measuring blood glucose levels at regular intervals afterward. If your fasting blood sugar is higher than 95 mg/dL, it points to gestational diabetes, according to the Mayo Clinic 5. But you will still need to complete the remainder of the test.

One hour after drinking the sugary solution, a normal blood sugar level should be below 140 mg/dL, per the Mayo Clinic. If your levels are higher, your doctor may recommend a second, more detailed oral glucose-tolerance test 5. But if your blood sugars are higher than 190 mg/dL, you will be diagnosed with gestational diabetes.

Read more: 5 Healthy Habits That Can Keep Blood Sugar in Check During Pregnancy

If you have a second test:

  • One hour after drinking the sugary solution, a normal blood sugar level is lower than 180 mg/dL
  • After two hours, a normal blood sugar level is lower than 155 mg/dL
  • After three hours, a normal blood sugar level is lower than 140 mg/dL

If one of these three levels is higher than normal, you will likely need to repeat the test in four weeks. If two or more of the levels are elevated, you'll likely be diagnosed with gestational diabetes.

Managing gestational diabetes will mean working to keep blood sugars within the normal range for the duration of your pregnancy 3. This will involve following a healthy diet and exercise plan and possibly taking medications.

Read more: Sample Diet Plans for People With Gestational Diabetes

Gestational Diabetes Complications

It's very important to manage gestational diabetes. Per the CDC, high blood sugar during pregnancy can 3:

  • Lead to preeclampsia
  • Cause problems during delivery
  • Make the baby grow very large (over 9 pounds), which can result in the need for a cesarean (C-section)or lead to injuries to the baby during delivery
  • Lead to longer recovery times after birth
  • Lead to type 2 diabetes in the mom-to-be
  • Cause rapidly changing blood sugar levels in the baby after delivery
  • Make it more likely that the child will be overweight or obese during childhood and adolescence — a risk factor for type 2 diabete 3s

Early and ongoing prenatal care is important in assessing your risk for gestational diabetes and for ensuring that your blood sugar levels remain within a healthy range. If you are pregnant but have not yet involved medical professionals in your prenatal care, make an appointment with your doctor as soon as possible.