Gestational diabetes mellitus (GDM) is a form of diabetes first diagnosed during pregnancy. It arises because placental hormones interfere with the body’s ability to use insulin effectively, leading to high blood sugar, or hyperglycemia. This poses risks to both the pregnant person and the developing fetus.
Tight control of blood sugar is necessary to prevent complications. These include fetal macrosomia, which increases the risk of birth injury and cesarean delivery, and neonatal hypoglycemia in the baby immediately following birth. Initial management of GDM focuses on lifestyle changes, including medical nutrition therapy and regular physical activity.
Blood Glucose Targets During Pregnancy
The immediate goal of managing gestational diabetes is to maintain blood glucose levels within a specific, narrow range that minimizes risks to the baby. These targets are significantly lower than those for non-pregnant individuals with diabetes. Monitoring involves checking blood sugar multiple times daily, typically upon waking and after meals, to ensure these goals are met.
The standard target for fasting blood glucose, measured before breakfast, is below 95 milligrams per deciliter (mg/dL). Many healthcare providers prefer an even tighter target, sometimes setting the fasting goal below 90 mg/dL.
Post-meal blood sugar levels are also closely monitored, with separate targets for one-hour and two-hour readings. The accepted one-hour post-meal target is below 140 mg/dL. If testing occurs two hours after the start of a meal, the goal is to remain below 120 mg/dL.
Defining Persistent Hyperglycemia
Achieving these tight glycemic targets through diet and exercise is the first step in GDM management. A single high reading does not automatically mean that medication is required; the decision to escalate treatment is based on a pattern of persistently elevated blood sugar levels.
Hyperglycemia is considered persistent when blood glucose readings remain above the established targets despite strict adherence to the prescribed diet and exercise plan for a defined period. This period is commonly set at one to two weeks of consistent monitoring and lifestyle effort. Some clinical guidelines specify that medication should be initiated if readings exceed the target levels more than one-third of the time over a one-week period.
Elevated readings indicate that the body’s natural insulin production cannot overcome the placental-induced insulin resistance. Documenting these consistently high levels in a log provides the medical team with the data needed to determine the appropriate timing and type of medication. The progression of GDM often makes it harder to control blood sugar as the pregnancy advances, frequently necessitating treatment changes.
Specific Glucose Levels That Trigger Insulin Therapy
When diet and exercise are not sufficient to meet the blood sugar goals, medication is introduced, with insulin being the preferred and safest option. The specific thresholds that trigger the initiation of insulin therapy are slightly higher than the target goals and must be consistently exceeded. For the fasting blood sugar, insulin is started if the level remains at or above 95 to 100 mg/dL.
If fasting levels are controlled but post-meal levels remain high, mealtime insulin may be added to the treatment plan. This intervention is recommended if the one-hour post-meal reading is persistently at or above 140 mg/dL, or if the two-hour post-meal reading consistently reaches or exceeds 120 mg/dL.
Some healthcare providers may first attempt oral medications, such as Metformin, before moving to insulin. However, insulin is considered the standard of care due to its established safety profile and effectiveness. If blood sugar levels remain uncontrolled on oral medication, insulin therapy will be necessary to bring the glucose back into the target range.
Managing Blood Sugar After Insulin Initiation
Once insulin therapy has begun, the immediate focus shifts to finding the correct dosage to return blood sugar to the target range. This process requires a temporary increase in the frequency of blood glucose monitoring, often involving checking levels four or more times each day. Increased monitoring helps the healthcare team determine how effectively the insulin is working and whether the dose needs adjustment.
Insulin doses are not static throughout the pregnancy and often require titration as insulin resistance naturally increases. A common titration algorithm involves increasing the insulin dose by a small amount, such as two units, every few days until the target levels are consistently achieved. This adjustment process demands regular communication with the diabetes care team, who review the blood sugar logs and guide dose changes.