Gestational diabetes mellitus (GDM) is a condition that develops during pregnancy when the body cannot produce or effectively use the insulin required to manage blood sugar levels. This condition affects between two and ten percent of pregnant women, and the standard method for initial detection is the 1-hour glucose challenge test, typically performed between 24 and 28 weeks of gestation. Receiving an abnormal result on this screening test can be alarming, but this initial test is designed to have a high sensitivity, meaning it often produces a high rate of false positives. A failed screening only indicates the need for further, more comprehensive testing, and it is not an automatic diagnosis of GDM.
The Next Step: Confirmation Testing
An abnormal result on the initial 1-hour glucose challenge test necessitates a follow-up diagnostic procedure: the 3-hour oral glucose tolerance test (OGTT). For this test, you must fast for at least eight hours prior to the procedure, consuming only plain water, and you should not smoke or exercise during this time.
The process begins with a blood draw to establish your baseline or fasting blood sugar level. Following this initial draw, you consume a sweetened liquid containing 100 grams of glucose within a few minutes. You must remain at the clinic for the entire duration of the test, as physical activity can interfere with the results.
Additional blood samples are then collected at the 1-hour, 2-hour, and 3-hour marks after finishing the glucose drink. A diagnosis of gestational diabetes is confirmed if two or more of these blood sugar levels—fasting, 1-hour, 2-hour, or 3-hour—are found to be above the established thresholds. If only one value is elevated, you may be asked to monitor your blood sugar at home or repeat the test later in the pregnancy.
Managing a Gestational Diabetes Diagnosis
If the 3-hour OGTT confirms a diagnosis of GDM, the focus immediately shifts to achieving and maintaining healthy blood sugar levels through active management. Management relies on modifications to diet and physical activity, often in consultation with a nutritionist or diabetes educator. Dietary adjustments center on careful carbohydrate counting and strategic meal timing to prevent sharp spikes in blood sugar.
You will be instructed on how to use a glucose meter to check your blood sugar levels multiple times a day, typically upon waking and after meals, to monitor the effectiveness of your management plan. Regular exercise helps your body’s cells use insulin more efficiently, thereby lowering blood glucose. Moderate activities, such as walking, swimming, or prenatal yoga, are recommended for 30 to 60 minutes a minimum of three times a week.
Should lifestyle changes alone not be sufficient to keep blood sugar within the target range, medication is introduced. Oral medications, such as metformin, may be prescribed to help reduce the amount of glucose produced by the liver or to increase insulin sensitivity. If oral medication is ineffective, or if blood sugar levels are significantly high, insulin therapy is introduced, which involves self-administered injections.
Protecting Mother and Baby Through Active Management
Strict control of blood sugar is paramount because uncontrolled GDM can lead to complications for both the pregnant person and the baby. High glucose levels in the mother cross the placenta, causing the baby’s pancreas to produce extra insulin, which leads to excessive growth, a condition known as macrosomia. A larger-than-average baby increases the likelihood of birth trauma, such as shoulder dystocia, and raises the probability of needing a Cesarean delivery.
For the baby, uncontrolled GDM carries the risk of hypoglycemia (dangerously low blood sugar) immediately after birth, as the baby’s body continues to overproduce insulin temporarily. Other neonatal risks include respiratory distress syndrome due to delayed lung maturity, and jaundice. Risks for the mother include an increased chance of developing preeclampsia, a serious condition characterized by high blood pressure and potential organ damage.
To mitigate these risks, active management includes increased fetal surveillance during the third trimester. This involves more frequent prenatal visits and additional testing, such as non-stress tests and biophysical profiles, to monitor the baby’s well-being. Regular ultrasounds are used to track the baby’s growth and ensure that macrosomia is not developing unchecked.
Postpartum Follow-Up and Future Screening
Gestational diabetes resolves immediately following delivery once the placenta, which produces the hormones that caused the insulin resistance, is removed. However, a history of GDM increases the future risk of developing Type 2 Diabetes. Up to 70% of women who experience GDM may develop Type 2 Diabetes later in life.
To confirm that blood sugar levels have returned to a healthy range, a postpartum screening is recommended using the 2-hour OGTT between six and twelve weeks after giving birth. If this test is normal, regular follow-up screening is necessary, with most medical guidelines recommending re-testing at least every three years. Maintaining a healthy diet and exercise regimen after delivery can substantially reduce the long-term risk of developing Type 2 Diabetes by up to 60%.