Diabetes and Pregnancy: A Guide to Gestational Diabetes

Diabetes that develops during the second or third trimesters of pregnancy is called gestational diabetes. It is becoming more common all over the world. Without treatment, gestational diabetes can affect your health and your pregnancy. It can also affect the health and development of the growing fetus. Here’s a guide to how gestational diabetes is diagnosed, why it matters, and how to prevent and treat it.

What causes gestational diabetes?

It’s not clear why some people develop diabetes during pregnancy. But, like all types of diabetes, gestational diabetes affects how the body responds to insulin. 

Insulin is a hormone that moves glucose (sugar) from the bloodstream and into cells for energy. The normal pregnancy hormones seem to weaken insulin — or cause "insulin resistance." Because insulin can’t do its job as well, glucose stays in the bloodstream instead of going into the cells. Insulin resistance begins around 20 weeks into pregnancy. After giving birth, insulin resistance and diabetes go away almost immediately.

How common is gestational diabetes?

Gestational diabetes is getting more and more common. In the U.S., gestational diabetes occurred in about 5% of pregnancies between 1991 and 2002. In another study from 1995 to 2009, the number increased to 10%. 

Most women have at least one risk factor developing gestational diabetes. But some don’t have any risk factors. It’s almost impossible to say that someone definitely won’t get gestational diabetes. That's why everyone needs a test for gestational diabetes during pregnancy. 

What are the symptoms of gestational diabetes?

Most people don’t have any symptoms from gestational diabetes. So most people don’t know they have gestational diabetes until they have a test for it. If your blood sugar is very high, you may experience symptoms like:

• Feeling very thirsty

• Having to go to the bathroom more often

• Feeling tired

• Having blurry vision

How do you diagnose gestational diabetes?

There are different strategies for diagnosing gestational diabetes. 

Blood tests in early pregnancy

If you have a higher risk for developing diabetes, you’ll need a blood test to look for diabetes during your first trimester.

The American Diabetes Association (ADA) and American College of Obstetricians and Gynecologists recommend early testing for gestational diabetes if you have any of the following:

• A history of gestational diabetes with other pregnancies 

• A history of having a baby with a high birth weight (more than 8 pounds, 13 ounces)

• A parent, brother, or sister with diabetes

• Age of 40 years or older

• A history of prediabetes, polycystic ovarian syndrome, cardiovascular disease, or high blood pressure

You will have a blood test to check your blood sugar level and hemoglobin A1C (HbA1C or A1C) levels. The ADA says that you have diabetes if you have any of the following:

• Fasting blood glucose of 126 mg/dL or above

• Symptoms of diabetes with a random glucose level of 200 mg/dL or above

• A1C of 6.5% or above

Glucose challenge test

Everyone should be screened for gestational diabetes between 24 and 28 weeks of pregnancy with a glucose challenge test.

To do the glucose challenge test, you’ll be asked to drink a premade drink that contains 50 g of glucose (sugar) in an 8 oz drink. An hour later, you'll have blood drawn to check your blood sugar. Here’s an overview of possible results:

• If your blood sugar is above 200 mg/dL, your healthcare provider may diagnose you with gestational diabetes without any other testing. 

• If your blood sugar is above 130 to 140 mg/dL but less than 200 mg/dL, you'll need a glucose tolerance test to confirm whether you have gestational diabetes.

• If your blood sugar is less than 130 mg/dL, then you don't have gestational diabetes.

Glucose tolerance test

A glucose tolerance test confirms whether or not someone has gestational diabetes. This test takes 3 hours, during which you have 4 blood draws. 

To prepare for a glucose tolerance test, you’ll need to fast for 8 hours before your appointment. When you arrive at the lab or office, you’ll have a blood test to check your blood sugar. You’ll drink a premade 8 oz drink that has 100 g of sugar. Then you’ll have your blood sugar drawn after hours 1, 2 and 3. 

You won’t be allowed to eat or drink anything except for water during these 3 hours, so you may feel nauseated or dizzy during this time. It’s helpful to have someone stay with you and to arrange a ride home afterward. 

You will get your results in a few days. Your healthcare provider will review what the results mean for you. In general, you have gestational diabetes if any one of the blood sugar levels is above the following limits: 

• Fasting level: 95 mg/dL or higher

• 1-hour level: 180 mg/dL or higher

• 2-hour level: 155 mg/dL or higher

• 3-hour level: 140 mg/dL or higher 

Why does gestational diabetes matter?

Gestational diabetes can lead to health problems for you and your baby.  

How gestational diabetes affects a baby

Gestational diabetes can increase your baby’s risk of several health problems, including:

• High birth weight: A heigh weight is more than 8 lbs and 13 oz (4,500 g, or more than the 90th percentile). Large babies can have a hard time getting out of the birth canal. Shoulder dystocia can occur. This is when the baby's shoulder gets caught on the mother’s pelvis during birth. This is an emergency and can result in the brain not getting enough oxygen, nerve damage, and other injuries. To avoid this serious risk, doctors often deliver the baby before the due date or plan for a C-section when a baby is suspected to have a high birth weight.

• Premature birth: Studies have shown a connection between preexisting maternal diabetes and birth before 37 weeks. Premature birth can increase a baby’s risk of developing infections and problems with breathing, vision, and the gut.

• Low blood sugar: Around 1 in 4 babies born to moms with gestational diabetes have low blood sugar at birth. This can lead to jitteriness and trouble feeding. In serious cases, seizures and brain injury can occur. If you have gestational diabetes, your healthcare team will check your baby’s blood sugar every 3 hours for a day to make sure they have a normal blood sugar. 

• High bilirubin: Babies are more likely to develop jaundice if their mother had diabetes. If your baby’s bilirubin level is high, they may need treatment with special light therapy. 

How gestational diabetes affects you

Gestational diabetes can affect your health, too. If you have gestational diabetes you’re at higher risk for:

• High blood pressure during pregnancy: Pregnancy-induced high blood pressure, preeclampsia, and eclampsia, are all serious health problems associated with high blood pressure in pregnancy. Studies show that gestational diabetes increases the risk of high blood pressure in pregnancy and preeclampsia. 

• Type 2 diabetes in the future: Studies show that having gestational diabetes increases the risk of developing Type 2 diabetes later in life. 

How do you treat gestational diabetes?

There’s treatment for gestational diabetes. With good blood sugar control, you and your baby can remain safe and healthy during pregnancy and beyond. Treating diabetes in pregnancy involves a few different strategies.

Glucose level monitoring

You’ll need to check your blood sugar (glucose) levels regularly at home with a small machine called a glucometer. You should be checking your glucose at least 4 times a day: once when you wake up, and once after each meal. 

Diet changes

Making changes to your diet is not easy at the best of times. This is especially true in pregnancy when nausea, tiredness, and cravings often influence what you eat.

But changing your diet is key to keeping your blood sugar in a healthy range. Most people are able to keep their blood sugar within normal ranges with diet changes. That means they don’t need medications or injections. 

A dietitian can be a great resource for helping you figure out a diabetes-healthy meal plan that also provides enough energy for you and your growing baby. You can also check out our complete guide on eating with diabetes for more advice.

Activity

A brisk walk 10 minutes after each meal is enough to lower the spike in glucose after eating. Of course, staying active in pregnancy has many other benefits:

• Eases backache

• Helps with constipation and bloating

• Increases energy

• Improves sleep and mood

• Strengthens core muscles and builds endurance (which you will need for delivery and beyond)

Weight gain tracking

Keep an eye on how much weight you’re gaining in pregnancy. Putting on too much weight can worsen gestational diabetes and its effects. Many people overestimate how much weight they should gain during pregnancy. If you’re labeled as overweight or obese, you may only need to gain between 11 and 20 pounds during your pregnancy. 

Medications

If diet and exercise do not work to bring glucose down to safe levels, then you’ll need to start insulin therapy. Insulin is safe for you and your growing baby. 

There are several different types of insulins, but all are taken as injections. Some of them act quickly and last a short time (useful after meals). Others work more slowly but last longer. Using a combination of different insulins lets you tailor your medications to your specific needs. 

The amount of insulin that you need depends on your glucose readings throughout the day. Your provider will teach you how to take your insulin and how to respond to high or low glucose levels.

Your healthcare provider may also recommend oral medications in addition to insulin. The most commonly used medications are glyburide and metformin. 

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Written by:

Peter Chen, MD

Peter Chen, MD, graduated from Vanderbilt Medical School and completed his residency in emergency medicine at Columbia and Cornell University hospitals. He has also worked in the field of biostatistics at Javeriana University in Bogota, Colombia.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

Reviewed by:

Adriena Beatty D.O., MBA, CPE

Adriena Beatty, DO, MBA, CPE, is an Army veteran and board-certified obstetrician and gynecologist with over 20 years of experience. She is a graduate from Tuskegee University with a degree in chemical engineering and chemistry.

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