Gestational Diabetes

Diabetes During Pregnancy

Written by Grazia Aleppo MD, FACE, FACP
Reviewed by Amy Hess-Fischl MS, RD, LDN, BC-ADM, CDE

What Is Gestational Diabetes?

Gestational diabetes sometimes develops when a woman is pregnant. It’s when the blood glucose level (blood sugar level) of the mother goes too high during pregnancy.

Having an elevated blood glucose level during pregnancy can cause problems for your baby—if it’s left untreated. Fortunately, doctors are vigilant about checking for gestational diabetes so that it can be identified and effectively managed. A pro-active treatment plan helps you have a good pregnancy and protects the health of your baby.

Gestational Diabetes Symptoms

Gestational diabetes doesn’t often cause noticeable symptoms for the mother. Other types of diabetes (eg, type 1 diabetes or type 2 diabetes) do cause symptoms such as increased thirst, but that is hardly ever noticed in gestational diabetes.

Because there aren’t often symptoms, it’s very important to be tested for a high blood glucose level when you’re pregnant. (Your doctor will most likely test you for gestational diabetes sometime between the 24th and 28th week. You can learn more about the diagnostic process here.) Then your doctor will know if you need to be treated for gestational diabetes.

Gestational Diabetes Causes and Risk Factors

Gestational diabetes develops when your body isn’t able to produce enough of the hormone insulin during pregnancy. Insulin is necessary to transport glucose—what your body uses for energy—into the cells. Without enough insulin, you can build up too much glucose in your blood, leading to a higher-than-normal blood glucose level and perhaps gestational diabetes.

The elevated blood glucose level in gestational diabetes is caused by hormones released by the placenta during pregnancy. The placenta produces a hormone called the human placental lactogen (HPL), also known as human chorionic somatomammotropic (HCS). It’s similar to growth hormone (so it helps the baby grow), but it actually modifies the mother’s metabolism and how she processes carbohydrates and lipids. HPL actually raises the mother’s blood glucose level and makes her body less sensitive to insulin—less able to use it properly. If the body doesn’t use insulin as it should, the blood glucose level goes up. The HPL hormone elevates the blood glucose level so that the baby gets enough nutrients from the extra glucose in the blood.

At 15 weeks, another hormone that affects the mother’s blood glucose level increases production: human placental growth hormone. This hormone helps regulate the mother’s blood glucose level, again to make sure that the baby gets enough nutrients. It can, however, cause the blood glucose level in the mother to go too high.

It’s normal for women’s blood glucose levels to go up a bit during pregnancy because of the extra hormones produced by the placenta. However, sometimes, the blood glucose level is too elevated.

The medical community isn’t sure why some women develop gestational diabetes, although there are several risk factors that make it more likely that you will develop it:


Gestational diabetes is diagnosed by checking your blood glucose level. Before doing that, your doctor will probably review your risk level and what risk factors you have; this is part of routine screening for gestational diabetes.

If the doctor feels you are at high risk for developing gestational diabetes, he or she will probably check your blood glucose level early in the pregnancy—sometimes as soon as they confirm that you’re pregnant.

If you aren’t at high risk, most doctors check the blood glucose level in the second trimester—around 24 to 28 weeks.

To diagnose gestational diabetes, your doctor will use the oral glucose tolerance test.  He or she will give you instructions on how to prepare for the test, but you won’t be able to eat anything for 8 hours before the test; you’ll be fasting.  This test is often done in the morning after an overnight fast.

On the day of the test, the doctor will test your blood glucose level at the beginning of the appointment; that’s called your fasting blood glucose level.

Then, you’ll drink 75 g of a very sugary mixture. Every hour for the next 2 hours, your blood glucose level will be measured.

If your blood glucose level is elevated (above normal) one or more times during the test, you have gestational diabetes.

The American Diabetes Association has set the following “above-normal” levels:

How Gestational Diabetes Can Affect Your Baby

When you have gestational diabetes, you must tightly control your blood glucose level. Talk to your healthcare professional regarding your individual blood glucose goals. Poorly controlled blood glucose levels—that stay too high for too long—can cause complications for your baby. 

Just because you’ve been diagnosed with gestational diabetes, that isn’t a guarantee that your baby will have all (or even any) of these complications. This is a list of what may happen if you don’t manage gestational diabetes.

Here’s how gestational diabetes can affect your baby at birth and right after birth:

Here’s how gestational diabetes can affect your child later on:

How Gestational Diabetes Can Affect You

As mentioned above, gestational diabetes often comes with no symptoms, so you probably won’t know that you have it until the doctor diagnoses it. However, gestational diabetes can still have an effect on you. 

Gestational diabetes can increase your risk of high blood pressure while you’re pregnant. Also, you may have a larger baby, which can make delivery difficult or require a C-section.

Gestational diabetes can also put you more at risk for developing type 2 diabetes later in life.

Gestational Diabetes Treatments

Treating gestational diabetes comes down to one main thing: controlling your blood glucose level so that it doesn’t go too high. You can control your blood glucose level by eating well, exercising, and perhaps taking insulin or another medication. Not every woman with gestational diabetes has to take a medication or insulin.

You’ll know how you’re doing controlling your blood glucose level by monitoring it several times per day. The doctor, a nurse, or a certified diabetes educator will explain how to use a blood glucose monitor, and they’ll give detailed instructions on when you should check your level. You’ll also be asked to keep track of your daily levels—that helps both you and the doctor know how you’re doing.

Delivery When You Have Gestational Diabetes

When you’re delivering your baby, the doctor will watch your blood glucose level. If your level goes too high during labor, the baby may release more insulin in response. That increases the risk of the baby developing low blood glucose (hypoglycemia) after birth.

You may need to have a C-section if your baby is too large.

Will Gestational Diabetes Go Away?

Most likely, after you deliver your baby, gestational diabetes should go away. About six weeks after delivery, your doctor will check your blood glucose level to see if it’s in the normal range again.

However, because you had gestational diabetes, you’re at a higher risk (a 33-50% increased risk) for having it again in another pregnancy. You’re also at a higher risk for developing type 2 diabetes. To learn how to prevent type 2 diabetes, read our article on prevention.