Large for gestational age (LGA) babies are those whose birth weight lies above the 90th percentile for that gestational age. Macrosomia, also known as big baby synrome, is sometimes used synonymously with LGA, or is otherwise defined as a fetus that weighs above 4000 grams (8 lb 13 oz) or 4500 grams (9 lb 15 oz) regardless of gestational age.