Gestational Diabetes Mellitus (GDM) is a type of diabetes that develops for the first time during pregnancy. It occurs when the body cannot produce enough insulin to meet the increased demands of pregnancy, leading to elevated blood sugar levels. While a diagnosis of GDM can be concerning, it is a manageable condition. With appropriate medical care and lifestyle adjustments, most individuals can have a healthy pregnancy and delivery.
Causes and Risk Factors of GDM
The development of GDM is linked to the hormonal changes of pregnancy. The placenta produces hormones like estrogen, cortisol, and human placental lactogen that can interfere with the mother’s insulin. This effect, known as insulin resistance, is a normal part of pregnancy that begins around 20 to 24 weeks. As the placenta grows, it produces more of these hormones, increasing insulin resistance.
In most pregnancies, the pancreas compensates by producing more insulin to keep blood sugar levels stable. GDM occurs when the pancreas cannot produce enough additional insulin to overcome the placental hormones’ blocking effect. This results in glucose building up in the blood instead of being used for energy.
Several factors can increase a person’s likelihood of developing GDM.
- A pre-pregnancy body mass index (BMI) in the overweight or obese range
- Being older than 25
- A personal history of GDM in a previous pregnancy
- A family history of type 2 diabetes
- Certain ethnicities, including individuals who are Black, Hispanic, American Indian, or Asian American
- Pre-existing conditions like polycystic ovary syndrome (PCOS) or prediabetes
Diagnosis and Monitoring
GDM often presents with no noticeable symptoms, so diagnosis relies on routine screening during prenatal care. Screening begins with a one-hour glucose challenge test, performed between 24 and 28 weeks of pregnancy. For this test, you drink a sugary solution, and a blood sample is taken one hour later to measure your blood sugar level.
If the results of the initial screening are high, a follow-up diagnostic test is required to confirm GDM. This is the three-hour oral glucose tolerance test (OGTT), which requires fasting overnight. You then drink a more concentrated glucose solution, and your blood is tested again at one, two, and three hours after. A GDM diagnosis is made if at least two of the blood sugar readings are above the standard threshold.
Once GDM is diagnosed, regular monitoring of blood sugar levels becomes a daily routine. This involves self-monitoring at home using a glucometer. Individuals are instructed to test their blood sugar upon waking (fasting) and again one or two hours after each main meal. This tracking provides feedback on how diet and exercise are affecting blood sugar, allowing for adjustments to the management plan.
Management Strategies
The primary goal of managing GDM is to maintain blood sugar levels within a target range for the well-being of both the mother and baby. For most, this can be achieved through dietary changes and regular physical activity, which are the first line of treatment.
A healthcare provider or registered dietitian will recommend a meal plan that focuses on balanced nutrition and controlled carbohydrate intake. This involves eating smaller, more frequent meals throughout the day to prevent blood sugar spikes. Emphasis is placed on whole grains, lean proteins, and vegetables while limiting sugary foods and refined carbohydrates. Tracking carbohydrate portions is a common strategy to help keep blood sugar levels stable.
Regular, moderate physical activity is also beneficial. Activities like walking or swimming can help the body use insulin more effectively, which in turn lowers blood sugar. It is important to discuss an appropriate exercise plan with a healthcare provider to ensure it is safe for the pregnancy.
When diet and exercise alone are not enough to keep blood sugar levels in the target range, medication may be necessary. This can include oral medications, such as metformin, or insulin injections. Insulin is a common and effective treatment for GDM as it does not cross the placenta in significant amounts.
Potential Effects on Mother and Baby
Effects on the Baby
If GDM is not well-managed, high blood sugar levels in the mother can cross the placenta to the baby. This can cause the baby’s pancreas to produce extra insulin, leading to a condition called macrosomia, where the baby grows significantly larger than average. A large baby increases the risk of birth injuries or the need for a Cesarean section (C-section) delivery. After birth, these babies are at risk for neonatal hypoglycemia (low blood sugar), jaundice, and breathing problems.
Effects on the Mother
For the mother, uncontrolled GDM increases the risk of developing preeclampsia, a serious condition characterized by high blood pressure during pregnancy. Due to the potential for a larger baby, there is a greater chance of needing a C-section for delivery. Having GDM in one pregnancy also increases the likelihood of developing it in future pregnancies.
Post-Pregnancy Outlook
For most individuals, blood sugar levels return to their normal range shortly after the baby is born. GDM resolves once the placenta, the source of the insulin-blocking hormones, is delivered. Because of this, GDM treatment is usually no longer needed postpartum.
To confirm that blood sugar levels have stabilized, a healthcare provider will recommend a glucose test, often an OGTT, around 6 to 12 weeks after delivery. This test is important to rule out the possibility of underlying type 2 diabetes that was present before or developed during pregnancy.
Having a history of GDM increases an individual’s lifetime risk of developing type 2 diabetes. The risk is higher within the first five to ten years after delivery. Therefore, maintaining a healthy lifestyle, including a balanced diet and regular exercise, is recommended to mitigate this future risk. Regular check-ups with a healthcare provider to monitor blood sugar are also advised.