What is the leading cause of macrosomia in newborns that are LGA?

• A. Genetic factors
• B. Maternal diabetes
• C. Excessive maternal weight gain
• D. Advanced maternal age

Answer: (B)

The leading cause of macrosomia, particularly in newborns classified as large for gestational age (LGA), is maternal diabetes. Maternal diabetes, whether it be preexisting type 1 or type 2 diabetes or gestational diabetes that develops during pregnancy, influences fetal growth significantly. Elevated glucose levels in the maternal blood result in increased insulin production in the fetus, leading to excessive fat deposition and subsequent macrosomia.

The relationship between maternal diabetes and macrosomia is critical since it actually produces a cascade effect not only on fetal growth but also on the newborn’s metabolic processes. The newborn may experience a higher risk of hypoglycemia right after birth due to potential overproduction of insulin, as their body adjusts to the new environment without the maternal glucose supply.

While genetic factors, excessive maternal weight gain, and advanced maternal age can also contribute to fetal growth, they typically do not have the same strong, direct link to macrosomia as maternal diabetes does. Maternal diabetes stands out as a primary risk factor due to its physiological effects on both the mother’s metabolism and the fetus's growth patterns.