Gestational Diabetes: What You Should Know

Learning about the signs, symptoms, and risks for developing gestational diabetes during your pregnancy is important for your health and the long-term health of the baby.

Written by Grazia Aleppo MD, FACE, FACP

What Is Gestational Diabetes?

While pregnant, women who have never had diabetes before but then develop high blood glucose levels may be diagnosed as having gestational diabetes,1 according to the American Diabetes Association.

It’s when the blood glucose level (blood sugar) of the mother stays high (hyperglycemia) because she is unable to make and use all the insulin needed to support the demands of the pregnancy. About 18% of women may experience gestational diabetes while pregnant but only 7% of those pregnancies will face complications.3,4

Having an elevated blood glucose level, or a glucose intolerance, while pregnant raises concerns not only for the mother but also can cause long-term problems for the baby—if it goes untreated. Fortunately, doctors are vigilant about checking for gestational diabetes so that it is identified and effectively managed early.

If you are pregnant and develop gestational diabetes, sticking to your treatment plan helps you have a good pregnancy and protects the health of your baby. It's important to know that having gestational diabetes raises a woman's risk 7-fold for developing type 2 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 blood glucose 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 somatomammotropin (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 maternal blood glucose level and makes a woman's body less sensitive to insulin—less able to use it properly. If the body doesn’t use insulin as it should, then the blood glucose levels will rise. The HPL hormone increases the blood glucose level so that the baby can get the nutrients it needs from the extra glucose in the blood.

At 15 weeks, another hormone—human placental growth hormone—also increases and causes maternal blood glucose level to rise. This hormone is also supposed to help regulate the mother’s blood glucose level to be sure that the baby gets the right amount of needed nutrients. 

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 goes up and stays high. Should this happen, gestational diabetes is associated with an increased risk of type 2 diabetes developing in the child.

While doctors aren’t clear about why some women develop gestational diabetes and others don't, there are several risk factors that make it more likely to occur:

How is Gestational Diabetes Diagnosed

Your doctor, most likely your obstetrician/gynecologist, but also your primary care practitioner, will likely review your risk level and discuss any risk factors you might have with you; this is part of routine screening for gestational diabetes.

If the doctor feels you are at high risk of developing gestational diabetes, s/he will probably check your blood glucose level early in the pregnancy—sometimes as soon as your pregnancy is confirmed. If you/'re blood sugar levels are in the normal range, you can expect the doctor to recheck your blood glucose levels again in the second trimester—around 24 to 28 weeks.

To diagnose gestational diabetes, your doctor will have you do an oral glucose tolerance test (OGTT), or glucose challenge.  S/he 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 over the course of two hours, your blood glucose level will be measured. 

The American Diabetes Association has set the following “above-normal” levels:1

If your blood glucose level is elevated (above normal) at least once during the test, your doctor will tell you that you have gestational diabetes. To reduce the risk of diabetes-related problems for you and your baby, follow your doctor's instructions. Some of the adjustments may be hard but like much of pregnancy, it's temporary and worth it!

Keep in mind, when blood sugar levels are not well controlled, the baby will gain more weight than is healthy, and you may face having to deliver a baby that weighs 10 pounds more.

If I Have Gestational Diabetes, How Will It Be Treated?

Treating gestational diabetes comes down to one key factor: controlling your blood sugar. The goal is to manage your blood glucose level so that it doesn’t go too high and stay high. This is accomplished by eating wisely, remaining physically active, and if needed taking medication to help keep your blood sugar levels in your target range.  

The importance of treating gestational diabetes gained attention following the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) trial, which demonstrated a direct link between continuous treatment of the maternal glucose levels and reducing negative outcomes.

You’ll know how well you’re doing controlling your blood glucose level by monitoring it several times per day. This is done by checking your blood glucose. Your health care practitioner will explain how to use a blood glucose monitor, and you'll receive detailed instructions on when and how often to check your blood sugar. You’ll also be asked to keep track of your glucose daily levels to help both you and the doctor know how well you are managing.

Delivery When You Have Gestational Diabetes

When planning for the baby's arrival,  the doctor will access the size of the baby to determine if you can deliver vaginally. If you have been able to keep your blood glucose well- controlled, your baby's weight is within an appropriate range, you don't have any other pregnancy concerns such as high blood pressure, and you are not on medication, than your labor should proceed just as it would if you didn't have gestational diabetes. Of course, your delivery team will monitor your blood sugar throughout.

If your baby is considered too large for you to deliver vaginally than you will likely be induced at weeks 38 or 39. You and your doctor may also decide that a cesarean (C-) section may be a better route for delivering the baby. Should blood sugar levels get 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 so a C-section may be considered.

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.

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.

Sources

  1. American Diabetes Association.  Standards of Medical Care in Diabetes—2018. Diabetes Care. 2018;41(S1):S137-S143. 
  2.  International Association of Diabetes and Pregnancy Study Group Recommendations on the Diagnosis and Classification of Hyperglycemia in Pregnancy. Diabetes Care. 2010;33:676–682
  3. Metzger BE, Lowe LP, Dyer AR, et al, for the HAPO Study Cooperative Research Group. Hypergylycemia and adverse pregnancy outcomes. N Engl J Med. 2008 May 8; 358(19):1991-2002.
  4. Ottawa Histology website.  The placenta.  Available at:  http://www.courseweb.uottawa.ca/medicine-histology/English/Reproduction/Placenta/Default.htm.  Accessed April 30, 2009.

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