According to the CDC (Centers for Disease Control and Prevention), between 2% and 10% of pregnancies in the United States are affected by gestational diabetes. Learning what your risk factors are for gestational diabetes can help you prevent it and manage it, if it should occur.
What is gestational diabetes?
Gestational diabetes, or GDM for short, is a type of diabetes that occurs during pregnancy, typically midway through the second trimester. Like pregnancy, gestational diabetes (GDM) is temporary. GDM will resolve in about 90% of women after they’ve given birth. It’s important to distinguish pregnancies accompanied by GDM from pregnancies that occurs in women with preexisting type 1 or type 2 diabetes.
If GDM isn’t treated, it can lead to problems for you and your baby. Also, having GDM means that you’re at an increased risk of getting type 2 diabetes later in life.
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What causes gestational diabetes?
The exact cause of GDM isn’t known, but this type of diabetes happens if your body can’t make enough insulin while you’re pregnant. Pregnancy is a time when a lot of changes occur in the body, and that includes changes in hormones, plus, of course, weight gain. Both hormone changes and weight gain affect how the body uses insulin; in fact, the body starts to use insulin less effectively, called insulin resistance. If you have insulin resistance your body needs more insulin to help keep blood sugar levels in a safe range.
Of note, all women have some insulin resistance during late pregnancy. But if you have insulin resistance before you become pregnant, you are more likely to have GDM.
What are the risk factors for gestational diabetes?
Some women are at higher risk of GDM. These risk factors include:
- Being older than 25
- Overweight or obesity
- Not enough physical activity
- Being Hispanic, African American, Native American, Asian, or Pacific Islander
- Family history of type 2 diabetes
- GDM with a previous pregnancy
- Having a baby who weighed more than 9 pounds at birth
- High blood pressure
- Heart disease
- Polycystic ovary syndrome
You might have noticed that many of the risk factors for GDM are the same as for type 2 diabetes. Some women with GDM will have none of the above risk factors, by the way. Why some women without any of the above risk factors develop GDM is unknown. What we do know is that the incidence of GDM in the U.S. has increased over the years, most likely due to the increasing prevalence of overweight and obesity in this country.
How is GDM diagnosed?
Your healthcare provider should test you for GDM, typically between 24 and 28 weeks of pregnancy, which is during the second trimester of pregnancy. You might get the test earlier if your provider believes that you’re at risk, based on the above risk factors. Blood sugars that are higher than normal early in your pregnancy may be a sign that you have type 1 or type 2 diabetes, rather than GDM.
There are different screening methods for GDM: a glucose challenge test and an oral glucose tolerance test (OGTT), as outlined by the American Diabetes Association.
The one-step strategy:
OGTT: This is done in the morning after fasting (not eating or drinking anything) overnight for at least eight hours. The diagnosis of GDM is make when any of these glucose levels are met or exceeded:
- Fasting: 92 mg/dl
- 1 hour: 180 mg/dl
- 2 hours: 153 mg/dl
The two-step strategy:
Glucose challenge test: You don’t need to fast for this test. You drink a drink that contains 50 grams of glucose and your blood glucose is checked an hour later. If your blood glucose is 140 mg/dl or higher, you will likely have an OGTT. If your blood glucose is 200 mg/dl or higher, you may have type 2 diabetes.
OGTT: For this test, you need to fast for at least eight hours. You’ll have your blood drawn, then you’ll drink a 100-gram glucose drink. Then, you’ll have your blood drawn every hour for three hours. High blood glucose levels at any two or more blood test times that exceed the following indicates GDM:
- Fasting: 95 mg/dl
- 1 hour: 180 mg/dl
- 2 hours: 155 mg/dl
- 3 hours: 140 mg/dl
If you are pregnant or planning a pregnancy, be sure to talk with your obstetrician about when and how you should be screened for GDM.
What are the risks of having GDM?
Having any type of diabetes is very serious due to possible complications that can occur. It’s important to note that women who have GDM can and do have successful, healthy pregnancies. But GDM must be carefully managed to ensure both a healthy baby and a healthy mother.
A lot happens in the body when a woman is pregnant. The hormones estrogen and progesterone rise, leading to increased insulin secretion and decreased production of glucose by the liver. The baby (fetus) uses a lot of the mother’s glucose, which can lead to low blood glucose levels in the mother. As pregnancy progresses, other hormones kick in, including human placental lactogen, cortisol, and prolactin. These hormones, combined with higher levels of estrogen and progesterone, can cause insulin resistance, which prompts the pancreas to secrete more insulin. In healthy, low-risk women, this isn’t a problem. But in women who are already at risk for diabetes, this isn’t good news; the pancreas can’t keep up with the demand for insulin. As a result, insulin resistance continues and GDM can set in.
Potential gestational diabetes complications
If GDM is not diagnosed or managed properly, some of the complications that can occur with the mother include:
- High blood pressure and preeclampsia, a serious condition that raises blood pressure and can be fatal.
- Cesarean birth (C-section).
- Increased risk of GDM with another pregnancy, as well as an increased risk of type 2 diabetes in the future.
- Increased risk of high blood pressure and high blood fats, raising the risk of heart disease.
- Macrosomia: This is a baby who weighs more than 9 pounds at birth. A large baby may mean that you need a Cesarean birth (c-section). A large baby can mean a higher risk of birth injuries, too.
Problems that can occur with the baby are:
- Early labor and delivery: These can lead to respiratory distress syndrome in the infant. Babies born with this may need help breathing until their lungs are fully formed.
- Low blood glucose in the baby due to high levels of insulin, raising the risk of seizures.
- Jaundice, due to the baby’s liver not being fully formed.
- Higher risk of obesity and type 2 diabetes later in life.
If you have GDM or are at risk of developing GDM, go to all of your prenatal appointments and learn what you can to manage your blood sugar levels to keep you and your baby as healthy as possible.
Want to learn more about gestational diabetes? Read “Glucose Test During Pregnancy for Gestational Diabetes,” “Treatment for Gestational Diabetes: Once You’re Diagnosed,” and “Gestational Diabetes: More Treatment Approaches.”