10 min read
Gestational diabetes mellitus (GDM) is a form of diabetes that develops during pregnancy in women who did not have diabetes before becoming pregnant. It occurs when your body cannot produce enough insulin to meet the increased demands of pregnancy, leading to elevated blood sugar levels. Gestational diabetes is one of the most common pregnancy complications, affecting approximately 2% to 10% of pregnancies in the United States each year. The good news is that with proper screening, monitoring, and management, most women with GDM have healthy pregnancies and deliveries. Understanding your risk factors, knowing what to expect from glucose screening, and learning how to manage your blood sugar can empower you to take an active role in your care.
During pregnancy, the placenta produces hormones that help your baby grow and develop. However, these same hormones can also make your cells more resistant to insulin — the hormone that moves glucose (sugar) from your blood into your cells for energy. This is known as insulin resistance, and it occurs to some degree in all pregnancies. In most cases, your pancreas compensates by producing extra insulin. When it cannot keep up with the increased demand, blood sugar levels rise, and gestational diabetes develops.
Gestational diabetes typically appears in the second half of pregnancy, most commonly between 24 and 28 weeks. It is different from pre-existing type 1 or type 2 diabetes, though women with undiagnosed type 2 diabetes may first be identified through pregnancy screening. In most cases, blood sugar levels return to normal after delivery, but a history of GDM is a significant risk factor for developing type 2 diabetes in the future.
While any pregnant woman can develop gestational diabetes, certain factors increase the likelihood. These include being overweight or obese before pregnancy (BMI of 25 or higher), having a family history of type 2 diabetes (particularly in a parent or sibling), a personal history of gestational diabetes in a previous pregnancy, a previous delivery of a baby weighing more than 9 pounds, polycystic ovary syndrome (PCOS), age older than 25 (with risk increasing with age), and belonging to certain racial or ethnic groups that have higher rates of type 2 diabetes, including African American, Hispanic, Native American, Asian American, and Pacific Islander populations.
Having one or more risk factors does not mean you will definitely develop gestational diabetes, but it does mean that your healthcare provider may recommend earlier or more frequent screening. Women with no risk factors can still develop GDM, which is why universal screening is recommended.
Current guidelines recommend that all pregnant women be screened for gestational diabetes between 24 and 28 weeks of gestation. Women with significant risk factors may be screened earlier, sometimes at their first prenatal visit.
There are two main screening approaches. The two-step method, which is more common in the United States, begins with a one-hour glucose challenge test (GCT). You drink a 50-gram glucose solution, and your blood sugar is measured one hour later. If your result is elevated (typically 130 to 140 mg/dL or higher, depending on your provider's threshold), you proceed to a three-hour glucose tolerance test (GTT), which involves fasting overnight, then drinking a 100-gram glucose solution and having your blood sugar measured at one, two, and three hours. A diagnosis of GDM is made if two or more values meet or exceed the diagnostic thresholds.
The one-step method uses a single 75-gram, two-hour oral glucose tolerance test performed in a fasting state. This approach, recommended by the International Association of Diabetes and Pregnancy Study Groups, diagnoses GDM if any single value is elevated. Your healthcare provider will determine which approach is most appropriate for your care.
The cornerstone of gestational diabetes management is blood sugar control, which involves a combination of dietary modifications, physical activity, blood glucose monitoring, and in some cases, medication.
Dietary management focuses on balancing carbohydrate intake to prevent blood sugar spikes. A registered dietitian or diabetes educator can help you develop a meal plan that includes appropriate portions of complex carbohydrates, lean proteins, healthy fats, and fiber-rich foods. Eating smaller, more frequent meals throughout the day (typically three meals and two to three snacks) helps maintain steady blood sugar levels. Limiting simple sugars, sugary beverages, and highly processed foods is generally recommended.
Regular physical activity, such as walking for 15 to 30 minutes after meals, can significantly improve insulin sensitivity and help lower blood sugar levels. According to current guidelines, most pregnant women can safely engage in moderate exercise unless their healthcare provider advises otherwise.
You will be asked to monitor your blood sugar levels at home, typically checking fasting glucose (first thing in the morning before eating) and one or two hours after each meal. Your provider will give you target ranges, which are generally a fasting level below 95 mg/dL and a one-hour postmeal level below 140 mg/dL or a two-hour postmeal level below 120 mg/dL.
When dietary and lifestyle measures alone are not sufficient to maintain blood sugar within target ranges, insulin therapy may be recommended. Insulin is safe for use during pregnancy and does not cross the placenta. Some providers may also use oral medications such as metformin or glyburide, though insulin remains the preferred pharmacologic treatment according to most guidelines.
When gestational diabetes is well managed, most women have healthy pregnancies and deliveries. However, uncontrolled blood sugar levels can lead to several complications.
For the baby, elevated maternal blood sugar causes the baby's pancreas to produce extra insulin, which can lead to macrosomia — excessive growth resulting in a birth weight of 9 pounds or more. Macrosomia increases the risk of birth injury, including shoulder dystocia (when the baby's shoulder gets stuck during vaginal delivery), nerve damage, and fractures. Babies born to mothers with poorly controlled GDM are also at risk for neonatal hypoglycemia (low blood sugar after birth), jaundice, respiratory distress syndrome, and a slightly increased long-term risk of obesity and type 2 diabetes.
For the mother, gestational diabetes increases the risk of preeclampsia (a serious blood pressure condition), the likelihood of needing a cesarean delivery, and the risk of birth trauma. There is also a higher chance of developing gestational diabetes in future pregnancies.
If your gestational diabetes is well controlled and no other complications are present, your healthcare provider may allow you to carry your pregnancy to your due date. However, if blood sugar control has been difficult or if the baby is measuring large on ultrasound, induction of labor or a planned cesarean delivery may be recommended, often between 37 and 39 weeks of gestation.
After delivery, your blood sugar levels will likely return to normal relatively quickly. Your healthcare team will monitor your glucose in the hospital after birth. The American Diabetes Association and ACOG recommend a postpartum glucose tolerance test at 6 to 12 weeks after delivery to confirm that your blood sugar has normalized and to screen for type 2 diabetes.
Crucially, evidence shows that women who have had gestational diabetes face up to a 10-fold increased risk of developing type 2 diabetes over their lifetime compared to women who did not have GDM. For this reason, ongoing screening with a fasting glucose or hemoglobin A1c test every one to three years is recommended. Maintaining a healthy weight, staying physically active, and following a balanced diet are the most effective strategies for reducing this long-term risk.
Research published in 2026 has identified promising biomarkers that may allow clinicians to predict gestational diabetes risk much earlier in pregnancy — potentially in the first trimester, well before the standard screening window of 24 to 28 weeks. These biomarkers include specific patterns of placental proteins, inflammatory markers, and metabolomic profiles that can be detected through a simple blood test.
Early identification of women at high risk for GDM could allow for earlier dietary counseling, lifestyle modifications, and closer monitoring, potentially preventing the condition from developing or reducing its severity. While this research is still being validated in larger clinical trials, it represents a significant step toward more personalized and proactive prenatal care. Discuss with your provider whether any early screening options are available based on your individual risk profile.
Your body and baby change dramatically across 40 weeks. This guide walks through each trimester’s key developments, recommended tests, and common symptoms.
Prenatal vitamins support your baby’s development and your health during pregnancy. Find out which nutrients matter most, when to begin taking them, and how to pick the right supplement.
Preeclampsia affects 5 to 8 percent of pregnancies and can develop rapidly. Understanding the warning signs, risk factors, and treatment options is critical for protecting both mother and baby.