What is the cutoff for hypoglycemia (low blood sugar) in pregnancy?

Hypoglycemia Cutoff in Pregnancy

The cutoff for hypoglycemia in pregnancy is 70 mg/dL (3.9 mmol/L), which represents the lower limit of the target range for pregnant women with diabetes. 1

Blood Glucose Targets in Pregnancy

According to the most recent American Diabetes Association (ADA) Standards of Care in Diabetes (2025), the recommended blood glucose targets for pregnant women with diabetes are:

• Fasting glucose: 70-95 mg/dL (3.9-5.3 mmol/L)
• 1-hour postprandial glucose: 110-140 mg/dL (6.1-7.8 mmol/L) or
• 2-hour postprandial glucose: 100-120 mg/dL (5.6-6.7 mmol/L) 1

These targets apply to women with type 1 diabetes, type 2 diabetes treated with insulin, and gestational diabetes treated with insulin. For gestational diabetes not treated with insulin, only the upper limits apply.

Hypoglycemia Risk in Pregnancy

Hypoglycemia during pregnancy presents significant risks:

• Occurs 3-5 times more frequently in early pregnancy than in the pre-pregnancy period 2
• Approximately 33% of women with pre-existing type 1 diabetes experience at least one severe hypoglycemic episode during pregnancy 3
• Risk factors include:
  • History of severe hypoglycemia in the year preceding pregnancy
  • Impaired hypoglycemia awareness
  • Long duration of diabetes
  • Low HbA1c in early pregnancy
  • Fluctuating plasma glucose values 2

Physiological Considerations

Several physiological factors affect glucose levels during pregnancy:

• Early pregnancy (first trimester) is characterized by enhanced insulin sensitivity and lower glucose levels, increasing hypoglycemia risk 1
• Around 16 weeks, insulin resistance begins to increase, with total daily insulin doses increasing linearly (5% per week through week 36) 1
• Insulin requirements typically double compared to pre-pregnancy needs 1
• Red blood cell turnover increases during pregnancy, causing A1C levels to be slightly lower than in non-pregnant individuals 1

Balancing Glycemic Control and Hypoglycemia Risk

While tight glycemic control is important to prevent adverse pregnancy outcomes, overzealous control may lead to:

• Increased risk of maternal hypoglycemia
• Potential fetal growth restriction
• Increased maternal morbidity 4

Therefore, glycemic targets should be achieved without significant hypoglycemia. If a woman cannot achieve the recommended targets without hypoglycemia, less stringent goals may be appropriate based on clinical experience and individualization of care 1.

Monitoring Recommendations

To minimize hypoglycemia risk while maintaining optimal glycemic control:

• Implement fasting, preprandial, and postprandial blood glucose monitoring 1
• Consider continuous glucose monitoring (CGM), especially for women with type 1 diabetes 1
• For women using CGM, aim for:
  • Time in range (63-140 mg/dL or 3.5-7.8 mmol/L): >70%
  • Time below range (<63 mg/dL or 3.5 mmol/L): <4%
  • Time below range (<54 mg/dL or 3.0 mmol/L): <1% 1

Common Pitfalls to Avoid

• Setting overly aggressive glycemic targets that increase hypoglycemia risk
• Failing to adjust insulin doses appropriately throughout pregnancy as insulin requirements change
• Not accounting for the increased risk of hypoglycemia in early pregnancy
• Overlooking the potential consequences of maternal hypoglycemia on fetal development
• Inadequate monitoring, especially during high-risk periods (early morning hours, before meals) 3

Remember that while the cutoff for hypoglycemia is 70 mg/dL (3.9 mmol/L), treatment approaches should be tailored based on the woman's specific clinical situation, history of hypoglycemia, and stage of pregnancy.