Reviewed by Qin Yang, M.D., Ph.D. 4/18.
Gestational diabetes, or diabetes that occurs in the second and third trimester of pregnancy and resolves at birth, occurs in approximately 9.2 percent of pregnancies in the United States. Gestational diabetes is defined as impaired glucose tolerance with onset or first recognition during pregnancy. It occurs in women who have never had overt diabetes before but who develop high sugar levels during pregnancy.
Similar to other types of diabetes, gestational diabetes affects how your cells use glucose. It causes high blood sugar that can affect your pregnancy and your baby.
While gestational diabetes can be an alarming complication, it can be controlled by maintaining a healthy diet, exercising, and taking medication if needed.
A mother’s blood glucose levels usually return back to normal after delivery. However, she should be closely monitored by her health care provider.
You will probably be tested for gestational diabetes between weeks twenty-four and twenty-eight of your pregnancy, using an oral glucose tolerance test to see how well your body responds to ingesting a large amount of glucose.
If you have a higher risk of gestational diabetes, your doctor may test you earlier, at your first visit during your pregnancy.
Causes of Gestational Diabetes
Researchers don’t know exactly what causes gestational diabetes and why some women develop it. However, it’s helpful to know what happens in the body when a woman does develop gestational diabetes.
According to the Mayo Clinic, the placenta produces high levels of various hormones which many of which impair the action of insulin within the body’s cells. As the baby grows, the placenta produces more and more insulin-countering hormones.
In gestational diabetes, the placental hormones create a rise in blood sugar that can affect the growth and health of your baby. The condition usually develops during the last half of pregnancy.
Potential Risk Factors:
Some known risk factors for gestational diabetes include the following:
- Family history- if a parent or sibling has type 2 diabetes
- Personal history- if you have a history of prediabetes or
- Women who are pregnant and over the age of 25 are more likely to develop gestational diabetes
- Overweight with a body mass index of 30 or higher
- Having had gestational diabetes in a previous pregnancy
- Having prediabetes
- Having given birth previously to a child weighing nine pounds or more
- Having polycystic ovarian syndrome (PCOS)
- In addition, the same populations at risk for type 2 diabetes—Latino Americans, African Americans, Pacific Islanders, and Asian Americans—are also at greater risk for gestational diabetes.
For most women, gestational diabetes doesn’t cause any symptoms. However, gestational diabetes screening is part of normal prenatal care.
Your doctor will evaluate your risk factors for gestational diabetes early in your pregnancy. If you have risk factors for gestational diabetes, your doctor will evaluate when screening is right for you.
Routine screening for gestational diabetes involves an oral glucose test. The test involves drinking a sweetened liquid, called Glucola, which contains 50 grams of glucose, also known as 50g OGTT. How the body metabolizes this solution is measured by a blood test.
Glucose Challenge Test Results:
A blood sugar level below 130 to 140 mg/dL: Usually considered normal
A blood sugar level higher than 140 mg/dL: Identifies 80% of women with gestational diabetes.
A blood sugar level higher than 130 mg/dL: Identifies 90% of women. Your doctor will recommend you taking another screening test that will require fasting.
Complications of Gestational Diabetes
Women who develop gestational diabetes have problems metabolizing glucose.
Their pancreas produces plenty of insulin (the hormone responsible for “unlocking” cells so that glucose can enter them and provide energy), but a condition known as insulin resistance prevents them from using it effectively.
When insulin doesn’t work properly, blood glucose (or blood sugar) builds up in the bloodstream, and gestational diabetes is the result.
The fetus of a woman with gestational diabetes may become large for a date as it stores the excess glucose it is receiving from the mother as fat, a condition known as “macrosomia.”
A large infant may have a more difficult time descending the birth canal. Other potential risks for the baby include hypoglycemia (low blood sugar) and jaundice.
A pediatrician or a neonatologist, (a physician who specializes in high-risk infant care), is often present at the births of gestational-diabetes babies to handle any potential complications.
Women who are able to effectively manage their gestational diabetes and keep blood glucose levels in the safe range dramatically reduce the risk of pregnancy complications.
Potential complications of uncontrolled gestational diabetes:
- Increased risk of developing gestational diabetes in subsequent pregnancies
- The risk of developing type 2 diabetes in the future
Treatment and Prevention
Gestational diabetes requires treatment with dietary changes, exercise, and/or insulin injections to keep maternal blood glucose levels as close to normal as possible and to prevent complications in both mother and baby.
Women with gestational diabetes are also encouraged to self-test their blood glucose levels often.
There’s no surefire way to ensure the prevention of gestational diabetes, but preconception planning may help to facilitate prevention by reducing some of the risk factors associated with gestational diabetes, such as excess weight.
Strategies are known to improve insulin resistance, and that may make a difference in the development of gestational diabetes, include:
- Maintaining a healthy weight
- Staying active
- Eating right
If you’re planning a pregnancy, talk to your doctor about your gestational diabetes risk and how to lower it. You can learn more about gestational testing goals and what to eat here. Read about considerations before planning your pregnancy here.
Qin Yang, M.D., Ph.D., is an Assistant Professor of Medicine, Physiology, and Biophysics at the Center for Diabetes Research in the Department of Medicine, Division of Endocrinology, at the UC Irvine School of Medicine. He specializes in Endocrinology & Metabolism and Internal Medicine.
- DeSisto CL, Kim SY, Sharma AJ. Prevalence Estimates of Gestational Diabetes Mellitus in the United States, Pregnancy Risk Assessment Monitoring System (PRAMS), 2007–2010. Prev Chronic Dis 2014;11:130415. DOI:http://dx.doi.org/10.5888/pcd11.130415.
- Mayo Clinic. “Gestational Diabetes.” Accessed March 15, 2018. https://www.mayoclinic.org/diseases-conditions/gestational-diabetes/symptoms-causes/syc-20355339
- American Diabetes Association. “Nutrition Principles and Recommendations in Diabetes.” Diabetes Care 2004 Jan; 27(suppl 1): s36-s36. https://doi.org/10.2337/diacare.27.2007.S36
- Hippokratia. “Gestational diabetes mellitus: why screen and how to diagnose.” Accessed March 15, 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2943351/