Hypoglycemia, or low blood sugar, occurs when the body’s primary energy source, glucose, drops below 70 milligrams per deciliter (mg/dL). While often associated with diabetes, pregnant individuals can experience low blood sugar due to the profound metabolic shifts that occur during gestation. The body must support both the pregnant person and the developing fetus, and disturbances to this delicate balance can cause glucose levels to fall. Understanding these specific causes, whether physiological or related to medical management, is important for a healthy pregnancy.
Physiological Changes in Early Pregnancy
The metabolic environment shifts dramatically in early pregnancy, setting the stage for potential dips in blood glucose. One significant change is a temporary increase in the body’s sensitivity to insulin. This heightened sensitivity, driven by hormonal changes, makes existing insulin levels more effective at clearing glucose from the bloodstream, leading to lower blood sugar, particularly when fasting.
The continuous transfer of glucose across the placenta to the developing fetus is another powerful factor, drawing glucose away from the maternal circulation. The fetus constantly consumes sugar even when the pregnant person is not actively eating. This uninterrupted drain, combined with an increased basal metabolic rate, causes the body to use up glucose stores more quickly.
This metabolic change often results in lower fasting glucose levels compared to before pregnancy. While the body adapts by using more fat as an energy source, this shift does not always prevent a drop in blood sugar, especially during overnight fasting. This early increase in insulin sensitivity is most pronounced during the first trimester, making pregnant individuals susceptible to non-treatment-related hypoglycemic episodes.
Hypoglycemia as a Side Effect of Diabetes Management
For pregnant individuals managing pre-existing Type 1, Type 2, or Gestational Diabetes Mellitus (GDM), low blood sugar is a frequent complication of treatment. The primary risk is a mismatch between the dose of glucose-lowering medication and the body’s fluctuating needs, which is challenging because insulin sensitivity changes dramatically throughout the trimesters.
The first trimester’s heightened insulin sensitivity often necessitates reducing the insulin dose by 10% to 20% to avoid low blood sugar episodes. Failure to adjust the dosage downward can lead to iatrogenic hypoglycemia, caused by medical intervention. As pregnancy progresses, placental hormones cause increasing insulin resistance, requiring higher doses; miscalculating these frequent adjustments can also lead to over-treatment.
Hypoglycemia can also result from the incorrect timing or dosage of oral medications, such as sulfonylureas, which stimulate the pancreas to produce more insulin. Taking these medications too far in advance of a meal, or taking too high a dose, can cause blood glucose to drop too low. “Insulin stacking,” where a correction dose is taken before the previous dose has finished working, is a common cause of severe hypoglycemia for those using insulin pens or pumps.
Lifestyle and Dietary Contributors
External factors related to diet, activity, and illness can significantly increase the risk of a low blood sugar episode. Inadequate caloric intake is a major contributor, often stemming from severe morning sickness or hyperemesis gravidarum. When severe nausea and vomiting prevent consuming enough carbohydrates, the body’s glucose reserves become depleted, triggering hypoglycemia.
Prolonged fasting periods, such as skipping a meal or going a long time between meals, interact poorly with the reduced fasting glucose levels of pregnancy. Since the fetus constantly consumes glucose, the pregnant person has less reserve sugar to rely on during these periods. Regular, small, well-balanced meals throughout the day are important for maintaining stable blood sugar.
Uncompensated strenuous exercise also uses up glucose stores more rapidly than usual. If a person exercises without consuming an appropriate carbohydrate snack or adjusting medication, the physical activity can drive blood glucose levels down quickly. This external stressor is compounded by the body’s underlying metabolic changes, increasing the likelihood of a low blood sugar event.
Recognizing and Treating Low Blood Sugar
Recognizing the signs of hypoglycemia is the first step toward immediate treatment. Common symptoms include sweating, shaking, nervousness, dizziness, a rapid heart rate, and confusion. Individuals may also experience blurred vision, intense hunger, or weakness.
The standard approach for treating an active low blood sugar episode is the “Rule of 15s.” This involves immediately consuming 15 grams of fast-acting carbohydrate. Examples include four ounces of fruit juice, a half-can of regular soda, or three to four glucose tablets. The simple sugar is absorbed quickly, raising blood glucose levels.
After consuming the carbohydrate, the individual should wait 15 minutes and then re-check their blood sugar. If the level is still below 70 mg/dL, the 15-gram carbohydrate treatment should be repeated. If an episode is severe, causing unconsciousness or an inability to safely consume sugar, emergency medical attention is required.