From the Guidelines
Fetal hyperglycemia and fetal acidosis are closely related conditions that occur when maternal hyperglycemia leads to excessive glucose transfer to the fetus, and management focuses on tight maternal glucose control throughout pregnancy, with target fasting glucose levels below 95 mg/dL and 1-hour postprandial levels below 140 mg/dL, as recommended by the most recent guidelines 1.
Pathophysiology
When a pregnant woman has poorly controlled diabetes or gestational diabetes, excess glucose crosses the placenta, stimulating the fetal pancreas to produce more insulin. This fetal hyperinsulinemia causes increased glucose utilization and oxygen consumption in fetal tissues, potentially leading to hypoxia. The hypoxic state forces the fetus to shift to anaerobic metabolism, resulting in lactic acid production and subsequent fetal acidosis.
Consequences
This metabolic derangement can have serious consequences, including increased risk of:
- Intrauterine fetal demise
- Neonatal hypoglycemia
- Respiratory distress syndrome
- Macrosomia
Management
Management typically involves:
- Dietary modifications
- Regular blood glucose monitoring
- Insulin therapy when needed
- Regular fetal assessment with non-stress tests, biophysical profiles, and growth ultrasounds to monitor for complications The underlying pathophysiology involves the maternal-fetal glucose gradient, where glucose freely crosses the placenta while maternal insulin cannot, creating this dangerous cascade of metabolic effects in the fetus when maternal hyperglycemia persists, as supported by the HAPO study 1 and subsequent guidelines 1.
Key Recommendations
Key recommendations for managing gestational diabetes mellitus (GDM) include:
- Using a one-step or two-step approach for diagnosis, with the one-step approach being associated with higher prevalence of impaired glucose tolerance and reduced insulin sensitivity in offspring 1
- Focusing on carbohydrate-controlled meal plans that promote optimal nutrition for maternal and fetal health, with adequate energy for appropriate gestational weight gain and achievement of normoglycemia 1
- Encouraging regular physical activity and lifestyle modifications after pregnancy to reduce the risk of subsequent diabetes 1
From the Research
Effects of Fetal Hyperglycemia and Fetal Acidosis
- Fetal hyperglycemia can lead to metabolic acidosis, as evidenced by a study where acute maternal glucose infusion resulted in maternal hyperglycemia, hyperinsulinemia, and an increase in the blood lactate level, as well as increased cord blood glucose, insulin, and lactate levels 2.
- Fetal acidosis can occur due to various factors, including hypoxia, and may not be directly caused by maternal glucose administration 3.
- Maternal hyperglycemia can lead to an increase in maternal and fetal lactate production, resulting in metabolic acidosis 4.
- Fetal hyperglycemia may lead to an increased fetal lactate production, contributing to metabolic acidosis 4.
Maternal Diabetes and Fetal Development
- Maternal diabetes can lead to severe problems, including spontaneous abortion, perinatal mortality, and congenital malformations, such as caudal regression syndrome, neural tube defects, and cardiovascular alterations 5.
- Gestational diabetes can induce increased fetal corporal fat and macrosomia with hyperinsulinemia, hypoglycemia, hypoxia, metabolic acidosis, and perinatal death 5.
- Hyperglycemia and hyperketonemia have been mentioned to have predominant roles in the pathogenic mechanism by which diabetes produces fetuses' abnormal development 5.