Large for gestational age (LGA) is a term used to describe infants that are born with an abnormally high weight, specifically in the 90th percentile or above, compared to other babies of the same developmental age. Macrosomia is a similar term that describes excessive birth weight, but refers to an absolute measurement, regardless of gestational age. Typically the threshold for diagnosing macrosomia is a body weight between 4,000 and 4,500 grams (8 lb 13 oz and 9 lb 15 oz), or more, measured at birth, but there are difficulties reaching a universal agreement of this definition.

Evaluating an infant for macrosomia or LGA can help identify risks associated with their birth, including labor complications of both the parent and the child, potential long-term health complications of the child, and infant mortality.